presents - chicago · pdf filepresents: p rocedural pain m ... use of checklists like this one...

JUNE 12, 2013

Chicago Veterinary Medical Association Shaping the Future of Veterinary Medicine - Promoting the Human-Animal Bond

Presents: PROCEDURAL PAIN

MANAGEMENT

With: ALICIA KARAS MS, DVM, DACVA

Chicago Veterinary Medical Association – June 12, 2013

Procedural Pain Management Alicia Z. Karas MS, DVM, DACVA Page 1 of 39

Overview of this series, “Procedural Pain Management”: We all want our patients to be calm, comfortable and to recover well after surgery. An individualized approach to each patient will keep the pain and stress of surgery and hospitalization as low as possible. These notes include descriptions of techniques and a selection of charts, tables and other useful documents to use in your clinic are included. Comfort, Calming and Communication and the Difference they Make for Pain and Worry ............................... 2 The effects of non-pharmacologic therapies, handling and environmental shifts can be significant on how our patients feel. This lecture will review methods for improving pain and the overall experience that veterinary patients have, by addressing handling, restraint, environment, techniques and communication. Choosing a Sedative or Premedication Protocol: The “Just Right” Approach for the Situation ........................ 6 Old and grumpy? Limited examination possible? Young and extremely fearful? Already painful? Disease challenges? Bad recovery from general anesthesia? Smile – because here are some approaches that you may find helpful to make your patients’ veterinary sojurn the best it can be. Don’t forget to refer to the Kitty Magic table too. Assessment of Pain in Hospitalized Dogs and Cats: Review of Principles .............................................................. 19 Assessment of acute pain is based on behavior which ideally includes dynamic and interactive components. Distinguishing pain from anxiety or dysphoria allows treatment goals to be optimized. Pain scales can be useful, but observers must be trained and limitations can be a problem. These presentations will review what we know about assessment of pain and then use real video presentations of dogs and cats after surgery or trauma to illustrate methods of assessment of pain so that when significant unrelieved pain is present, additional measures to treat it can be undertaken. Surgical and Procedural Pain Management ....................................................................................................................... 25 The objective of this lecture is to help the practitioner determine an initial analgesic strategy and to be confident in how to add other therapies when they are warranted. Timing, interactions with anesthetics and other medications, individualized therapy and use of adjunct drugs to augment comfort will be discussed using a case based platform. In addition, we will touch on the transition to “go home” analgesia and advice for clients. Use of Local Anesthetics for Perioperative and Procedural Pain Control .............................................................. 32 You may not know just how incredibly versatile, inexpensive and safe local anesthetics can be for reducing pain; in fact, many of us have lots of “old baggage” in our minds about the perils of using them in dogs and cats. This lecture will review the indications, effects, safety and methods of administration (including novel ones) of local anesthetics. Other documents: The Many Ways to Work Magic on Kitties .......................................................................................................................... 36 A table with guidance for procedural sedation in cats of all conditions and moods. Guide to Use of Peri-Anesthetic Anticholinergics: ........................................................................................................... 37 This chart can help you decide whether to use these drugs. Checklist for Anesthesia and Surgery .................................................................................................................................. 38 You may have heard about the alarming rate of “never events” (things that should not happen) in human hospitals. Use of checklists like this one can reassure you that you have taken all the precautions necessary to avoid never events in your clinic. Post-Anesthesia Temperature Support Monitoring ....................................................................................................... 39 Avoid distress and adverse events in your patients by proper thermal support after anesthesia.



COMFORT, CALMING AND COMMUNICATION AND THE DIFFERENCE THEY MAKE FOR PAIN AND WORRY

Alicia Z Karas MS, DVM, DACVA Tufts University Cummings School of Veterinary Medicine, North Grafton, MA, TuftsVETS, Walpole, MA

Each veterinary patient who enters the clinic is like a human toddler at the doctor’s office: they don’t know why they are there and they are frequently very afraid of the place. We are obligated to understand that struggling, growling, scratching and biting are natural ways for them to tell us they are afraid or that we are hurting them. Responding with “dominant” behavior such as yelling or excessive force will make the experience more awful for them and fear can make pain worse. For this reason, we must use skillful assessment of behavior, low stress handling, sedation and reassurance to accomplish medical care and cause as little mental and physical stress as possible. This lecture will review methods for improving pain and the overall experience that veterinary patients have, by addressing handling, restraint, environment, techniques and communication. I. COMFORT Picture this: being held still by one person who extends your arm and squeezes it to make your vein stand out, while another person grabs your hand and sticks a large needle through your skin and pokes around to hit the vein. Or, you are suddenly put on a table, turned on your back and restrained by one or more people. Now, envision that you don’t know these people, and that you don’t know why they are doing this, and that you have back pain, you hate having your feet touched, you have foot, hip or elbow arthritis, or have difficult veins to hit. You might struggle, scream or bite! Our patients have no idea why they should submit to this sort of thing – and reactions are not because they are inherently evil, they are natural responses. While truly irate and or dangerous patients may require a degree of forcible restraint, the author has found that use of a very brief restraint period for the purpose of giving sedation or analgesia to lessen the impact of further manipulations makes a tremendous difference to the amount of force required, and to the safety of the patient and the staff. Even if a patient is relatively cooperative, there are many things that will contribute to a more comfortable clinical experience. Assess the patient: Robust, friendly and healthy? Elderly or debilitated? Difficulty walking or rising? Fearful, anxious or in obvious pain? Handling in general should take these factors into consideration. Some patients may feel very insecure when placed on a table, working with them on the floor may be better, at least until the moment you need them at waist height. Knowing how the patient is likely to tolerate handling is key to preventing anxiety or pain. Lifting: We so often lift large dogs by placing one arm under their abdomen, but the author feels that this is not a good way to lift them. A dog with strong abdominal muscles can tolerate this, but if they have back or hip pain, or abdominal pain or fragile structures inside, the pressure on the organs, or the torque that this places on the low spine can cause pain and even damage. It is far more neutral to support the pelvis with one arm between the hind legs or around the rump. Restraint: Less is often more and most veterinary professionals instinctively know this. If the limb seems stiff when you extend it, then there may be lots of significant pain, and force will make this worse. Often, rolling a patient into lateral position will permit access to a hind leg with more neutral amount of force, and this is also ideal for patients with back or neck pain, as the spine is not subjected to pressure. If it is possible, working with large breed dogs on the floor is more suitable for them. Also, when restraining small dogs or cats on tables, a rubber mat for traction makes them much less uneasy. Handling and positioning anesthetized patients: It is essential to consider the negative impact of non neutral positioning of the head, limbs, spine and jaw when patients are positioned while taking radiographs, sedated for procedures or anesthetized for surgery. Even robust patients can be harmed by non neutral positioning, rope or gauze ties, sand bags, ECG clips, cautery plate handles and dental gags.



The use of spring loaded mouth gags in cats for oral procedures has been associated with post anesthetic brain injury and death and the author recommends that these not be used at all in cats, and used only for short procedures in dogs as the spring tension puts a huge amount of stress on the muscles and TM joint. Limbs that are positioned above the heart for long periods of time may become ischemic. The chest must not be restricted by sand bags, heavy blankets, or equipment. Moving the patient while under anesthesia should consist of careful cooperative and neutral handling. Twisting or bending the spine and traction on the legs can result in iatrogenic pain and even dislocations and spinal injury. When patients who are weak or painful are placed in recovery, a neutral and natural position is best, the author generally advocates a sternal position, supported by a pillow or wall, with the head slightly elevated but the oral cavity oriented downwards, in case a patient has fluid in the mouth that might be aspirated into the lungs. Large weak or sedated and confused old dogs frequently have difficulty adjusting their posture from a lateral recumbent one. In addition, if the abdominal contents are not compromised, then it is very kind to express the bladder prior to ending anesthesia delivery, so that patients who can’t quite get up yet do not have to face the distress of full bladder or soiling themselves. Reducing pain of procedures: In some cases you will find that the animal’s reaction to restraint signals fear or painfulness and this is when sedation or analgesia makes a tremendous difference. The author prefers to use intramuscular (or sometimes oral transmucosal) premedication prior to placing a catheter for anesthesia as the patient will struggle less and experience much less pain or stress. But one simple technique can help reduce even the pain of intramuscular or intravenous needle sticks – and your own dentist or phlebotomist as probably used these on you without your knowing! This is to use a physical distraction technique. Many people learn to gently tap a patient on the head (mental distraction), but it actually works better if you take a fold of skin in your hand (distant from the injection site) and gently squeeze to give a mechanical (but not painful) stimulus, the patient will often not notice the needle stick. There is a very sound neurophysiologic basis for this technique, similar to the skillful use of a lip twitch in horses – or your dentist pinching your cheek while injecting local anesthesia with a long needle. Also, once a catheter site is clipped, if the patient objects to the needle stick (often happens in small dogs), placing an ice cube on the skin for 30 - 60 seconds usually desensitizes the skin sufficiently to avoid a reaction. Substrate: Our clinics often have a good supply of pillows and blankets and we use them to good effect. Picture how much more comfortable you would be in a hospital bed when the nurse props your back or head firmly. But the traumatized or chronically painful dog may require more than this. If you sit in a run, even on a thick layer of quilts, you may find that you develop pressure induced “pins and needles” or need to readjust your position often to avoid pain. The author has found that an ultra-delux synthetic fleece from the listed supplier, “faux sheepskin” is useful for wicking away urine, and provides a washable and very comfortable bed. Cats also love this. http://www.palacepet.com/ Or, for the wholesale product: https://www.montereymills.com/Products/PetFabrics.aspx Slings and traction for dogs: Slipping and falling cause more pain and can even lead to severe injury. Slings can be easily made from large trash bags, but beware that patients with back or abdominal pain may find that strong pressure of an abdominally placed sling is uncomfortable. Thus, a “figure 8” sling can be employed that helps support the pelvis itself, or a sling can be placed under the thorax instead. Traction is a really big problem; our clinics have easy to clean but slick floors for old dogs with long nails and dry paws. One solution is to provide boots for hospitalized patients, and there is a temporary type of rubber bootie (PAWZ, http://pawzdogboots.com/) that is less cumbersome than a more permanent boot for hospitalized dogs. Alternatively, there are spray on rosin preparations (such as “Show Foot” http://www.showdogstore.com/bio-groom-show-foot) available from dog grooming suppliers, that can help dogs find traction in the clinic.

http://www.palacepet.com/

https://www.montereymills.com/Products/PetFabrics.aspx

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Thermal support: Shivering has two downfalls; one is that it is deleterious to animals with poor circulatory, respiratory or anemia conditions, and that hypothermia is immunosuppressive, leading to increases in wound infection rates. The other is that it is really distressing. Thus thermal support during anesthesia or after bathing will reduce distress and improve outcomes. Being too warm is also a stressor, and cooling measures can include provision of cool surfaces – even a nearby ice pack, dampening paws or ears (but isopropyl alcohol smells and tastes terrible, so just use water) and fans. It is essential that when using hot water heating pads in cages, that space be provided for patients to move off the heat if they need to. It should go without saying that regular electric heating pads should NEVER, EVER be used in vet clinics. They can cause burns. In addition, the use of microwaved hot fluid bags can also cause thermal burns and use on patients is not advisable. The hospitalized chronic pain patient: We see more dogs and cats that are on multiple medications for chronic pain, and they may be admitted for emergency or elective procedures that are unrelated to their chronic pain. If we abruptly discontinue a pain medication, no matter what the reason, the patient is likely to experience much more pain in hospital, and have a more complicated recovery. It is thus essential to know what medications the owner has been giving, to have them bring those with the pet and to either continue giving them or to substitute other suitable medications (if oral medications can’t be given). It is very helpful for the nursing staff to help owners and veterinarians realize the need for continued chronic pain relief. Additionally, the chronic pain patient and any patient with moderate to severe acute pain will benefit more from analgesia and sedation for procedures such as radiography. Struggling is a risk factor for causing more pain. II. CALMING Anxiety and fear make for lots of distress. While we can make use of drugs to help with these, there are many things that are non-pharmacological that will help reassure the patient. Observing and responding to behavioral cues requires experience and training. Not all veterinary professionals are adept at this. Verbal cues: There are people who use two unfortunate kinds of voice around animals. One is a loud, warning or threatening voice. Yelling NEVER is a calming influence, for human or non human animals. There simply is, in the author’s opinion, never a need for becoming a worse threat to the animal than we already are. Alternatively, people instinctively use a high pitched, squeaky voice around animals. Most canine behaviorists will suggest that dogs find this somewhat distressing (because dogs use high pitched or squeaky sounds to signal anxiety). Those who work with horses naturally use a soothing, low pitched and drawn out voice to settle their patients, and we ought to think about this when working with dogs. Also, many dogs know some human language cues, such as “walk”, “out” and of course, their names. While we can use these “do you want to go OUT?” (this is asking the animal a question), some behaviorists caution us not to ask animals to do things like “sit” or “down” or “stay” because, if the dog does know these cues, using them in an aversive situation actually “poisons” the cue for the future (after all, you are not asking them to sit for a cookie, but to submit to restraint, which punishes them for the behavior and reduces its likelihood in future). Presence and touch = the absence of isolation: Dogs and cats in the clinic may be stressed by the presence, sounds and conveyed threats of other animals nearby. But most socialized animals, whether overtly friendly or not, find isolation stressful. Evidence is accumulating for the beneficial effects of companionship (social support) and touch in both human and non-human animals, and the benefits include improved levels of stress and immuno-enhancement. While we are often so busy that spending time with animals in a non-medical way, sitting, brushing, stroking, in or out of the cage, is not possible, it is useful to remember that these efforts are not just nice but may help recovery. Owner visits should be encouraged, even though it can often be distracting to daily routines. Odor cues: Many of the odors that we find associated with cleanliness or pleasure are inherently noxious to animals. Use of non-scented detergents and disinfection preparations should be encouraged.



If something smells strong to you, imagine how an animal with the nose of a dog finds it! There are new disinfectants which make use of hydrogen peroxide with no perfume and which do not corrode metal or rubber, and break down into oxygen and water that are very useful in the vet clinic. On the other hand, we can make good use of some odors - synthetic pheromones (feline facial pheromone, or FFP, and dog appeasing pheromone, or DAP) to help patients. The author routinely sprays a face cloth or small towel with the appropriate pheromone and places it in cases with nervous or excited patients. III. COMMUNICATION Talking with colleagues: The language that we use to help characterize our patients should involve mutually agreed upon terms; ones that are easily understood by people with various language backgrounds. Thus, the use of scoring systems for temperament, degree of sedation, illness, or pain are of enormous benefit. Many is the time that one of us has called a colleague to tell them something important about a patient, only to be misunderstood. It is also important to keep detailed notes in a patient’s record about what things they like or dislike (e.g. caution around men, will chew blankets, must wear E collar), what sedation techniques worked and as well, what medications they reacted negatively to (e.g. no hydromorphone). Communicating with the owner: The pet is precious to the owner. And, thus, every word that conveys your compassion and the things that you have done to help the patient is valuable. Rather than saying (or writing on the cage label) that an animal is “fractious” or “fearful”, imagine the difference if the cage said “go slow, I’m nervous about treatments”, or, “I don’t like needles”, or “I’m grumpy today”, or “if you muzzle me, I can be good for treatments.” It is important to clearly convey when an animal has no bite inhibition, especially if someone has been bitten, but think of how you can say this without having it sound critical. And in the author’s opinion, no cage should ever say “painful” – because that suggests that we have not addressed this. Rather, perhaps, say “my injury (or my condition) requires very gentle handling (or thick bedding).” You can use these “code words” to say what is needed and to communicate your compassion. IV. THE OVERALL BENEFITS Mind-body. It’s no longer just a nice theory, but a discipline with accumulating evidence. Optimal healing requires not only expert medical treatment, but reduction of fear, pain and stress. The process of dying is also one with a critical need for emotional and physical comfort. So, by bringing these methods into your practice, you will not only help the patient, but you will impress owners and engender their trust and gratitude. But lastly, you will have less job stress and go home at the end of the day, knowing that you did your utmost to help the patient, so you will be better off as well. Additional reading: Carney, HC, Little, S, Brownlee-Tomasso, D et al. (2012) AAFP and ISFM Feline-Friendly Nursing Care Guidelines. J Fel Med Surg 14, 337-349. Rodan, I, Sundahl, E, Carney, H et al (2011) AAFP and ISFM Feline-Friendly Handling Guidelines. J Fel Med Surg 13, 364–375 Yin, S. (2009) Low Stress Handling Restraint & Behavior Modification in Dogs and Cats. (Textbook and DVD) Cattle Dog Publishing



CHOOSING A SEDATIVE OR PREMEDICATION PROTOCOL: THE “JUST RIGHT” APPROACH FOR THE SITUATION


Making your patients happy on the “before” or “after” side of a procedure is a challenge. Listed here are some protocols for sedation and pain management (and induction and monitoring too) for a number of common surgeries. But also described here are some things that the author has found to be good rules of thumb or techniques to deal with unanticipated problems. The crazed ones: We know them – the greyhound who melts down as soon as they arrive at the clinic, the cat who did let you examine him, once, but has had it, or the patient who comes in the door –freaking-out. There are a few things you can do here.

1. If you know that a patient is a nervous wreck, dispense a dose of injectable acepromazine (0.01 – 0.05 mg/kg, depending on what you would give them IM) to the owner ahead of time, no needle – just have the owner squirt it in the pet’s mouth about 20 minutes prior to leaving the house. It is better than tablets (which I do not use at all). It might not make them into well adjusted model citizens, but it will help when you go to premed with the other half of the cocktail. 2. If they are crazed enough, consider ALSO having the owner give a dose of gabapentin (5 – 10 mg/kg) PO in a small treat or meatball in the morning – in addition to the acepromazine. Gabapentin is anxiolytic, as well as analgesic and sedative. You might have to adjust your premed and anesthesia dose if this makes them really gorked. You MUST also tell the owner that sleepy is FINE and is the GOAL here, so they don’t fret.

Shifting your paradigm: If you are not used to having your patients be sedate and quiet prior to or after anesthesia – take note: 1. It is perfectly fine if they are really sleepy preop – especially if they are nervous, or have lots of preop pain. BUT your anesthetist must get used to:

a) being careful to ONLY give the amount of induction drug that they need – more than they need results in hypotension, hypoventilation and sometimes poor saturation

b) the MAC sparing effects of profound premeds!!! Turning the vaporizer setting down, sometimes WAY down, is nerve wracking at first. Use your skills to assess patient depth; don’t worry if they are only on a 0.5 % isoflurane setting. THIS is cutting edge balanced anesthesia.

2. They should NOT be so sleepy postop that they can’t be extubated within 20 minutes of turning off the vaporizer. If prolonged time to extubation occurs, then you probably had them too deep. EXCEPTIONS: brachycephalic breeds and after laryngeal tie back, dogs will often snooze happily for up to an hour, because they have not been able to breathe so easily for a long time. If a patient has had a pure agonist opioid in the premed and seems too sleepy (unarousable, not swallowing) then try this technique: draw up a 0.1 mg/kg dose of butorphanol and give half of it IV, wait 3 minutes then give the other half – the patients will nearly always spit out the ET tube and be comfy – you don’t have to worry about reversing their analgesia, it’s usually pretty good with a multimodal technique. Moving target? An intraoperative technique to consider: let’s say your dental patient, having extractions, local blocks just didn’t do the trick, or, surgical patient under anesthesia - and they are responding by taking heaving breaths, moving chewing, etc. First, is the heart rate and blood pressure high? If so, they aren’t deep enough, and you should adjust depth of inhalant (and it’s another lecture altogether to help coach you how to do this efficiently). Can’t increase anesthetic plane because of hypotension? Check heart rate – if it’s low, then give a dose of anticholinergic IV (and be ready to adjust



depth, they may lighten as their BP rises and inhalant is re-distributed to muscle from brain). If they are responding intermittently during painful probings, then try giving a 0.6 mg/kg dose of ketamine IV. It will help your opioid work better, often just does the trick. If you used ketamine for induction, then chances are it won’t help to give more ketamine. Don’t try this if the patient has epilepsy, until we know more about its effects in these patients at micro doses. Call it like it is: Vocalizing and thrashing after extubation can be due to emergence delirium, pain, anxiety or opioid induced dysphoria. See the assessment file in this series to understand how to differentiate between these phenomena. Emergence delirium occurs when the excitatory centers of the brain “wake up” before the

inhibitory centers do. It is usually very short lived, less than 3 minutes after extubation. However, patients who were very nervous prior to anesthesia and who didn’t get a good robust anxiolytic like acepromazine in the premed may be more likely to experience emergence delirium. Puppies and kittens may also be more prone to this.

Pain will make recovery rocky. If you haven’t chosen a good combination of analgesics and sedatives, your patients might have rough recoveries. Palpating the surgical site (and the whole patient if you don’t get pain at the surgical wound) can give you an idea whether it is due to pain.

Anxiety in recovery often leads to emergence delirium, but might also make patient more prone to dysphoria.

Dysphoria is described in the assessment file of this series. If a dog or cat is being very violent, might hurt themselves, or you, then a great option is to use a low dose of dexdomitor IV to calm them. It has analgesic and sedative properties, so if you don’t know, it is a good choice. The author draws up a 3 mcg/kg (0.003 mg/kg) dose of dexdomitor and gives half. If this doesn’t do it, then give the other half. You can always reverse it if the patient is too sleepy but in fact they usually sleep for about 30 minutes and then can be re-assessed. I generally avoid this in cats and dogs with heart murmurs, however, you can assume that violent struggling is pretty bad for the heart too and very oxygen consumptive. So sometimes you may have to elect to use this even in patients with some degree of cardiac disease. If you find that there is significant pain (see assessment file), then it is best to give some additional analgesia. NSAIDS can take up to 2 hours for onset. Buprenorphine starts to take effect in about 15 minutes but may require 30 minutes to show best effect. If you have used buprenorphine in the premed, it is always a great idea to try to add to it – higher total doses of 0.15 – 0.03 mg/kg can work wonders for pain in dogs and cats. If you used a pure agonist opioid, then giving another ¼ to ½ the dose you originally gave may be the best option. Acepromazine takes as long as 20 minutes for full onset of action. If you give ace to a patient who is waking up badly, but it was just a touch of emergence delirium, or if they are actually painful; the result will be an overly sedated or under-analgesed patient. I usually wait to see how they recover and if they are whiny, struggling to stand, or thrashing and they a) calm down when you sit with them, and b) don’t respond to palpation of their wound, then a small dose of acepromazine (0.01 to 0.025 mg/kg IV or OTM) can do the trick. You can always give more, but you can’t reverse its actions. If the patient will not calm when petted or spoken to, and you have eliminated the possibility of undertreated pain, then there is a good chance that it is dysphoria. Giving these patients dexdomitor or acepromazine may calm them somewhat but if it is truly dysphoria, then they will “relapse” into the vocal/struggling behavior in a short time. When you think it might be dysphoria, then draw up your 0.1 mg/kg butorphanol and give it IV. If your patient calms down, seems more oriented, then you did the right thing. If you do this and it wasn’t dysphoria, you still need to hunt for the cause and proper treatment but you haven’t hurt anything.



Cats that are thrashing and struggling after surgery who were pre-medicated with pure agonist opioids might be hyperthermic. Giving that 0.1 mg/kg butorphanol, maybe some cool SQ fluids, wetting their paws (with water) and even a dose of acepromazine to vasodilate them, will often set things right. Always try some general nursing care if the patient can’t settle after recovery. Bladder full? Did not defecate this morning, owner running late? Regurgitated intraop, burning esophagus? Re-position (dogs in lateral find it stressful), neutral posture? And, if it’s an hour after recovery and the dog or cat just won’t settle, try a small meatball. Empty stomach makes me sad too. Just make sure that they can swallow and don’t choke on it. It will often settle patients, probably by altering their brain neurotransmitter levels (like sleepy after your turkey dinner or warm milk). The following protocols are ones I generally use for routine procedures. I will modify this document over time; consider it a work in progress.



ABDOMINAL EXPLORE (Exploratory Laparotomy) Pre-med Options:

Hydromorphone (avoid in cats) (0.1mg/kg) + Midazolam (0.1-0.2mg/kg) Oxymorphone (0.1mg/kg) + Midazolam (0.1-0.2mg/kg) Methadone** (0.3 mg/kg) + Midazolam (0.1-0.2mg/kg) Fentanyl (3-5µg/kg) + Midazolam (0.1-0.2mg/kg) [more critical patients] add Glycopyrrolate as needed you may choose to omit midazolam if you are giving premed IV, or use midazolam IV prior to

induction with propofol Induction Options:

Ketamine**-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume) Propofol (4mg/kg) Without Pre-med: Ketamine** (2mg/kg) + Fentanyl (3µg/kg) + Midazolam (0.1mg/kg) [most

critical patients] Avoid:

Drugs that cause splenic enlargement or unstable hemodynamics: Acepromazine, (but OK to use ace for stable cystotomy patients)

To Do’s and Watch For’s:

may need two catheters [largest bore preferred] is blood loss or sepsis a potential problem? Think of letting ER know about assistance and or

blood products need ventilator is usually advised consider lidocaine and ketamine CRI for multimodal analgesia for most canine patients, just

ketamine CRI for feline patients w/ out heart murmurs, and Fentanyl CRI as additional intra-op for critical patients

if there is likely to be a problem with “full stomach” or vomiting, then induce patient with head above body, keep head up, avoid gagging during intubation and inflate cuff ASAP while head is up – you can recheck it later but if patient accidentally regurgitates, you have avoided aspiration

stable patients can have some acepromazine in recovery if they seem to need it + IF GDV/Splenectomy

watch for VPCs – treat runs with Lidocaine if HR >160bpm, dropped pulses, or low BP watch and replace blood loss; blood type +/- coag useful prior to surgery esp. if hemoabdomen

Must Have Monitors:

ECG SpO2 Blood Pressure(NIBP,

doppler)

EtCO2 Temperature Esophageal Stethoscope

+ IF Septic Abdomen/Cholecystectomy/Cholecystoenterostomy/EHBTO

Pre-op: dopamine CRI calculated, +/- blood typed, coag profile, Vit K if obstructive Feline patients

several units of blood available (prefer whole blood) ECHO (heart status prior b/c ↑↑ fluid/blood transfusion therapy)

Peri-op: (esp. feline patients) Bleed back line (prefer lumen) E-tube placement + u-cath? Monitor Hypo K+- supplement KCL – recheck every 45 min



AMPUTATION - LIMB Pre-med Options:

Methadone** (0.5 mg/kg) or Hydromorphone (0.1 mg/kg) + Acepromazine** (0.01-0.05mg/kg) +/- Glycopyrrolate (0.01mg/kg)

Hydromorphone (0.1mg/kg) + Dexmedetomidine (2-8mcg/kg) Oxymorphone (0.1mg/kg) can be used in place of other pure mu opioid, preferable mu opioid

for cats Substitute benzodiazepine for acepromazine when indicated

Induction Options:

Propofol (4mg/kg) Ketamine**-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume)

Avoid:

Putting a catheter in the leg that is being amputated To Do’s and Watch For’s:

Epidural – Duramorph (0.1mg/kg) for BOTH fore and hind limb cases Local Blocks if applicable (total dose bupivacaine in canine patient is 2 mg/kg q 6 hours, and in

feline patient is 1 mg/kg q 6 hours) Consider soaker catheter!!! See wound soaker catheter protocol Two IV catheters in case of blood loss? Lidocaine (dogs only) + Ketamine CRI/ Fentanyl CRI if no epidural or as needed

Lidocaine (150mg) + Ketamine (30mg) in 500mL LRS NSAID postop if applicable Oral gabapentin (5 – 10 mg/kg BID) pre and post op for 10 – 14 days

Must Have Monitors:

ECG SpO2 Blood Pressure (NIBP, doppler)

Temperature Esophageal Stethoscope

CASTRATION – FELINE Pre-med Options:

Premed Only Castration Cocktail IM [supplement with mask inhalant if necessary] Ketamine (6-10mg/kg) Dexmedetomidine (8-10mg/kg) Butorphanol (0.2mg/kg)

Ketamine (6-8mg/kg) + BAG (0.1mL/kg) Induction Options if needed:

Ketamine-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume) Propofol (4mg/kg)

… with “Castration Cocktail”:

+/- inhalant by mask if not enough Have ETT ready in case of an emergency



Analgesia: Lidocaine testicular block (2mg/kg divided between testicles) Buprenorphine (0.01mg/kg) NSAIDs: Meloxicam (0.1-0.2mg/kg) or Onsior

To Do’s and Watch For’s: Cocktail has quick onset! Make sure surgeon has proper supplies and is ready; watch cat after

premed! CASTRATION – K9 Pre-med Options:

BAG (0.1mL/kg) + Buprenorphine (0.01mg/kg) [post-induction] Hydromorphone** (0.1mg/kg) + Acepromazine (0.025-0.05mg/kg) +/-Glycopyrrolate

(0.01mg/kg) Hydromorphone** (0.1mg/kg) + Dexmedetomidine (2-8mcg/kg) Oxymorphone (0.1mg/kg) can be used in place of pure mu opioid Substitute benzodiazepine where needed

Induction Options:

Propofol (4mg/kg) Ketamine-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume)

Analgesia:

Lidocaine testicular block (2mg/kg divided between testicles) Buprenorphine (0.01mg/kg) if BAG pre-med NSAIDs: Meloxicam (0.1mg/kg) or Carprofen (2.2 mg/kg)


patient getting light when pulling on testicle (testicular block very helpful in avoiding this) Must Have Monitors:

ECG SpO2 Blood Pressure

(NIBP, doppler)




CESAREAN SECTION If Puppies/Kittens are Alive: Pre-med Options:

None Butorphanol (0.2mg/kg) +/- Atropine (.02mg/kg)

Induction Options:

Propofol (4-8mg/kg) Maintenance with Sevoflurane Avoid:

Long lasting and irreversible drugs. Many drugs will pass through the placenta and into neonate system.

Do not overheat the babies! They only need an ambient temperature of 80°F. To Do’s and Watch For’s:

keep patient left side down to keep pressure of the aorta (don’t position in dorsal until necessary)

Surgeon can do a line block of linea alba and ventral midline with lidocaine < 4 mg/kg; or infiltrate body wall and SQ w bupivacaine (1.5 mg/kg) post-op

Have additional propofol to use as needed Pain Management: give Buprenorphine (0.01mg/kg) AFTER puppies have been taken out Single dose meloxicam 0.1 mg/kg SQ for bitch postop If opioids are given before puppies/kittens are out, remember that the babies may need to be

reversed with oral transmucosal naloxone. If Puppies/Kittens are Dead: Treat as OHE/ABDOMINAL EXPLORE Must Have Monitors:

ECG SpO2 Blood Pressure

(NIBP, doppler)


CYSTOTOMY Pre-med Options:

Hydromorphone (0.1mg/kg) + Acepromazine (0.01 – 0.05 mg/kg) or Midazolam (0.1-0.2mg/kg) Oxymorphone (0.1mg/kg) + Acepromazine (0.01 – 0.05 mg/kg) + Midazolam (0.1-0.2mg/kg)

(for cats) Since surgery is caudal abdomen, acepromazine can be used if needed add Glycopyrrolate as needed

Induction Options:




To Do’s and Watch For’s: Analgesia for stable cystotomy in patient w normal renal function may include NSAIDS Hyperkalemia – leads to metabolic acidosis

Do not anesthetize hyperkalemic patients until you FIX their K+!!! Ventilate patient to eucapnia (respiratory alkalosis) Treat with insulin and dextrose (cause K+ to move into cell) Have calcium gluconate ready in case of emergency (3 cc per cat injected slowly IV)

Must Have Monitors:

ECG SpO2 Blood Pressure, (NIBP, doppler)


DENTAL PROCEDURES Pre-med Options:

Butorphanol 0.2 mg/kg + acepromazine 0.01 – 0.05 mg/kg +/- glycopyrrolate 0.01 mg/kg Add ketamine 3 – 5 mg/kg IM if fractious and only in cats with no heart murmur If extractions: use local blocks with bupivacaine

Minor: Buprenorphine (0.01mg/kg) in addition to above Major or several: substitute Hydromorphone (0.1mg/kg) or Oxymorphone (0.01mg/kg)

for butorphanol

Induction Options: Propofol (4mg/kg) Ketamine-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume)

Avoid:

Watch for bradycardia during strong stimulation of oral cavity, premed with glycopyrrolate especially in brachycephalics and “little white breeds”

No spring loaded mouth gags EVER in cats To Do’s and Watch For’s:

Local blocks – cats: 1.5 mg/kg bupivacaine, dogs: 2 mg/kg bupivacaine Add NSAID postop in patients with normal renal/hepatic function Airway protected – check to make sure there are no leaks by ETT

Must Have Monitors:

ECG SpO2 (if poss.) Blood Pressure (NIBP, doppler)

Temperature



DIAPHRAGMATIC HERNIA Treat like ABDOMINAL EXPLORE + THORACOTOMY Avoid:

Peak inspiratory pressure greater than 20cm H2O, esp. if problem is chronic Elevation of hind end of animal; this increases pressure on the diaphram.


Ventilator a must! May need to manual ventilate until chest is cleared of abdominal organs; may need PEEP

Elevate thorax to keep abdominal organs from entering chest Watch saturation!!!

Must Have Monitors:



ENDOSCOPY Pre-med Options:

Acepromazine (0.025-0.5 mg/kg) Butorphanol 0.2 mg/kg + acepromazine 0.01 – 0.05 mg/kg +/- glycopyrrolate 0.01 mg/kg Butorphanol 0.2 mg/kg +/- glycopyrrolate 0.01 mg/kg

Induction Options:


Avoid:

Pure agonist opioids increase pyloric sphincter tone To Do’s and Watch For’s:

Note: with minimal premed used, patients tend to need higher levels on inhalant anesthesia Vagal reflex when passing scope

Must Have Monitors:


Temperature



ENUCLEATION Pre-med Options:

Hydromorphone (0.1mg/kg) + Acepromazine (0.025-0.05mg/kg) OR Midazolam (0.1-0.2mg/kg) + Glycopyrrolate (0.01mg/kg)

Oxymorphone (0.1mg/kg) can be used instead of Hydro for cats Buprenorphine 0.02 mg/kg + Acepromazine (0.025-0.05mg/kg) + Glycopyrrolate (0.01mg/kg) Use Glycopyrrolate, unless contraindicated, because of vagal reflex

Induction Options:

Propofol (4mg/kg) Avoid:

Ketamine if patient has or is prone to glaucoma in other eye To Do’s and Watch For’s:

Add NSAID if indicated

Must Have Monitors: ECG SpO2 Blood Pressure (NIBP, doppler)


THORACIC OR LUMBAR LAMINECTOMY Pre-med Options:

Hydromorphone (0.1mg/kg) + Acepromazine (0.025-0.05mg/kg) +/- Glycopyrrolate (0.01mg/kg)

Hydromorphone (0.1mg/kg) + Midazolam (0.1-0.2mg/kg) + Glycopyrrolate (0.01mg/kg) Oxymorphone (0.1mg/kg) can be used for cats

Induction Options:



Ventilate as needed – positioning can cause thorax restriction Blood loss!! Watch for hyperthermia

Consider LK CRI as additional inter-op pain management in dogs ( Lidocaine (150mg) + Ketamine (30mg) in 500mL LRS run at 10 ml/kg/hr) or ketamine only CRI in cats

Must Have Monitors:





LATERAL SUTURE / TTA/ TPLO/MPL / ARTHRODESIS Pre-med Options:

Hydromorphone (0.1mg/kg) OR Oxymorphone (0.1mg/kg) OR Methadone (0.3 mg/kg) + Acepromazine (0.025-0.05mg/kg) +/- Glycopyrrolate (0.01mg/kg)

Induction Options:



Dogs: lidocaine/ketamine CRI Consider epidural morphine for more painful surgeries Postop NSAID if indicated Postop cryotherapy

Must Have Monitors: ECG SpO2 Blood Pressure (NIBP, doppler)

Temperature Esophageal

Stethoscope MASTECTOMY Pre-med Options:

Hydromorphone (0.1mg/kg) OR Oxymorphone (0.1mg/kg) OR Methadone (0.3 – 0.5 mg/kg) + Acepromazine (0.025-0.05mg/kg) +/- Glycopyrrolate (0.01mg/kg)

Induction Options:



Local blocks/ line blocks – can be very painful procedure if full chain removed Consider epidural duramorph NSAID if applicable LK CRI intraoperatively for pain management

Lidocaine (150mg) + Ketamine (30mg) in 500mL LRS (dog) Ketamine CRI - cat

Must Have Monitors:

ECG SpO2 Blood Pressure (NIBP, Doppler)




MASS REMOVAL Pre-med Options:

Minor (dog, for cat options see chart) BAG (0.1 ml/kg) + Buprenorphine (0.01mg/kg) OBAG (0.1 mL/kg) + Buprenorphine (0.01mg/kg)

Major Hydromorphone (0.1mg/kg) or Oxymorphone (0.1mg/kg) or Methadone (0.3 – 0.5 mg/kg) +

Acepromazine (0.05 – 0.025mg/kg) or Midazolam (0.2 mg/kg) +/- Glycopyrrolate (0.01mg/kg) Induction Options:

Propofol (4mg/kg) To Do’s and Watch For’s:

MCTs – add Benadryl and famotidine with premed Blood loss Soaker catheter for large masses NSAID if applicable

Must Have Monitors:



OHE – FELINE Pre-med Options: See chart – Kitty Magics Induction Options:

Ketamine-Diazepam/Midazolam (1mL/20# - 50/50 mix by volume) Propofol (4mg/kg)


consider using NSAIDs for additional pain management Must Have Monitors:

ECG SpO2 Blood Pressure (Doppler)




OHE – K9 Pre-med Options:

BAG or OBAG (0.1mL/kg); Buprenorphine (0.01mg/kg) post-induction Hydromorphone (0.1mg/kg) + Acepromazine (0.025-0.05mg/kg) + Glycopyrrolate (0.01mg/kg) Add Ketamine (2-3 mg/kg) if not a happy camper Oxymorphone (0.1mg/kg) can be used in place of Hydro

Induction Options:



consider using NSAIDs for additional pain management Must Have Monitors:

ECG SpO2 Blood Pressure (NIBP, Doppler)


**Specific medication hints: Acepromazine – very elderly or calm older patients may only need 0.01 mg/kg IM and we use half the IM dose when giving it IV Hydromorphone – if you give hydromorphone IM, it often causes vomiting, but if you give an entire 0.1 mg/kg dose IV, the pet usually gets briefly nauseous and does not vomit. If pet is already sedate, or on opioids, or under anesthesia, you should titrate IV doses “to effect” i.e. do not give the entire dose IV because the respiratory and cardiovascular depression will be too great. Ketamine – generally should not use ketamine in the following patients: cats with murmurs or gallops (OK in dogs w heart murmurs), patients with glaucoma or having intraocular surgery, patients with epilepsy, cats with renal dysfunction or UO Methadone – If patient has no catheter and is very excited or anxious, methadone is not a good IM premed choice as it doesn’t lead to much sedation. Very healthy and calm patients may benefit from a 0.5 mg/kg IM dose rather than 0.3 mg/kg



ASSESSMENT OF PAIN IN HOSPITALIZED DOGS AND CATS: A VIDEO ASSESSMENT LABORATORY


Abstract: Assessment of acute pain is based on behavior which ideally includes dynamic and interactive components. Distinguishing pain from anxiety or dysphoria allows treatment goals to be optimized. Pain scales can be useful, but observers must be trained and limitations can be a problem. These presentations will use real video presentations of dogs and cats after surgery or trauma to illustrate methods of assessment of pain so that when significant unrelieved pain is present, additional measures to treat it can be undertaken.

Pain assessment is challenging, yet something we all want to do well. Most experts agree: studying behavior is the best way to assess pain in animals. Animals live mainly in the present, meaning that it is hard for them to understand that our veterinary care is intended to help them in the future. They don’t know that it will be better tomorrow – and so we really must help them cope with how it is right now for them. A dog or cat recovering from a major surgery, or trauma might show credible evidence of pain – vocalizing (yelping or screaming), biting at or looking at the injured body region, struggling, or trying to bite people nearby in their distress. Sometimes pain is quite obvious from observing animal behavior – but it isn’t always. Some of the most painful patients are absolutely quiet and still, and may or may not vocalize when manipulated. There is no gold standard measurement of pain. Skillful reduction of negative experiences in the acute pain context requires pharmacologic therapy as well as physical, environmental, and emotional support. Assessment methods are subjective; they depend on an observer’s level of experience and preconceived beliefs. There is no substitute for directly examining patients to guide treatment; thus training yourself and caregivers to observe and communicate your findings is essential. Assessment of Pain: Painful animals (and humans) may have elevated blood pressure, respiratory rate, or heart rate and in the past, pain assessment schemes have included physiologic variables. Current evidence does not favor this approach, because the process of taking physiologic measurements can alter the variable itself. Also, they are non-specific, elevated in fear, stress, shock, during recovery from anesthesia, and may be normal when the patient is experiencing pain. While there are good reasons to use vital signs for regular patient health monitoring, consider these two points. One is the value of the quality of respiratory effort; a quietly resting patient should have a relatively slow respiratory rate and an end- expiratory pause, similar to that occurring during sleep. The other is that as opioids and acepromazine may cause lower rectal temperatures, low body temperature is not per se, a contraindication to giving additional medications. Instead, use a sedation scoring system, (see Figure), as guidance in medicating for pain. You may have to translate this chart into language that works for your situation and culture, but it is helpful to post this on the wall of the clinic for reference. If a patient is alert enough to respond to you when you greet him, then more pain medication should not be harmful.

There are essentially four aspects of behavioral observation that may be used to assess whether an animal is adequately comfortable.

1. Look for the impact of pain on normal behavior. When pain impacts “activities of daily living” to the

point where the patient can’t cope physically and mentally, recovery is impacted and the humans around that pet will be distressed. It’s helpful to know what is “normal” for that patient in the clinical environment – was he originally anxious, subdued, resistant, or friendly & social? Normal orientation in the cage/run, posture and facial expression are key observations; most dogs will face and watch the outside of the enclosure when awake. For cats, this is more variable. Learning facial expression language is important, stressed dogs tend to show white around the eye (whale eye), furrowed brow, lips pulled back and ears often attuned to the challenge; relaxed dogs a more



elliptical eye shape, smooth brow, and alert or relaxed ears. Generally, willingness to engage in normal postures or activities can be used as comfort indicators. Upon rising, dogs often do a vigorous “whole body shake” or stretch. In the authors’ experience, an injured dog will terminate the shake at the level of injury (i.e. stop at diaphragm with abdominal or back pain) or fail to shake at all (head/neck, severe debilitating pain), and when this is seen to be restored to normal, it indicates comfort. Social interest in nearby patients is a normal activity for many. With mental dullness, or decreased response to handling or approach of an observer, the condition should be rated “abnormal”; and efforts taken to determine the cause. In severe adverse states, (which may be due to pain, nausea, weakness, electrolyte abnormality, etc.); animals appear unable to respond to or unaware of human presence. It the cage door is open and the patient doesn’t seem to notice you, intervention is urgently needed. Conversely, dogs observed to be dull and depressed by remote video responded to the entry of a human by tail wags and greeting (which was, however, still subtly diminished from normal quality) (Hansen, 2003). This may lead to the conclusion that such animals are not in significant pain when, in fact, additional analgesia reverses their dullness when alone and improves vigor of greeting and interactions with humans. Also, not all animals will be able to exhibit “normal” behavioral repertoire. Critically ill or chronically debilitated animals may not be able to walk or react as healthier animals do, and so use of other assessment methods is essential.

2. Look for abnormal behaviors indicative of pain. Hansen (2003) characterized new onset pain

behaviors as occurring for a variety of reasons: as protective against exacerbation of pain (guarding or escape), as expressions of pain that are designed to distract or call attention, as learned responses, or due to physical impairment. Although it is possible an animal might limp from non-painful limb dysfunction, administration of an effective analgesic helps distinguish this by improving the lameness if due to pain. Grooming and behaviors directed at the painful body part, (looking, biting or chewing, kicking, rubbing, and paw or head shaking) may be new onset indicators of pain. Abnormal postures frequently occur in painful animals, and include writhing, hunching, inability to lie down or to roll into sternal, stiffness, walking on toes, and abnormal tail position. These depend upon the affected body part. Abdominal and thoracic pain often causes an increase in tone of abdominal muscles (“splinting”) and breath-holding or shallow respiration. Spontaneous vocalization is often assumed to be a universal pain symptom; however, vocalization in dogs after surgery is less specifically indicative of pain and more commonly a sign of anxiety, and is not a feature of pain in cats unless pain is extreme. A normal or abnormal behavior must occur with enough frequency that it can be seen during a relatively short observation period, or it is not as useful to the observer.

3. Use evoked behavioral responses - pain in relation to movement or palpation. In human clinical

studies, pain scores are often similar in treatment versus control groups when pain is assessed at rest. When dynamic pain is studied (ask subjects to do a task, sit up or cough) differences between groups in mean pain score become evident. Inactivity is protective of some types of pain, but not all. Most currently accepted veterinary pain scoring systems include an interactive component, e.g., ambulation, or wound palpation. This is of significant value in detecting moderate to severe pain in animals whose behavior may appear normal at rest.

4. Use behavioral changes in response to analgesic administration - observing return of normal

behavior, or cessation of abnormal behavior in response to analgesic administration is a convincing gauge that pain was indeed present when it is observed. If your exam does not reveal pain at the surgical site – consider other sources of discomfort. These may be unrelated to surgery, such as: full bladder, constipation, bandage pain, joint pain from positioning during surgery, and in some cases – hunger!

Signs of pain: You must know the species, and sometimes the breed or strain. In order to detect abnormalities, the observer must be very astute. Also, realize that pet owners may be better at “reading”



their pet than a stranger. Listed below, are just some of the “new onset pain behaviors” shown by animals in acute severe pain (adapted from Karol Matthews excellent chapter in the Veterinary Clinics of North America Small Animal Management of Pain, July 2000 Vol 30 issue entitled: Pain Assessment and General Approach to Management). Note that signs may vary depending on the individual, a stoic animal may not vocalize and may appear still and withdrawn. You may be able to add to the list as you observe animals. Also notice that some of these signs may be due to pain, or to other factors (i.e. whining might occur in an animal that needs to urinate, or one that is anxious or wants out of the cage). Dogs: abnormal sitting or lying posture restlessness, thrashing (less common) splinting of abdomen, “prayer position” whining, groaning, screaming (less common) limping, unwilling to get up, unwilling to lie down lack of appetite trembling increased respiratory rate, expiratory grunt bulging eyes, dilated pupils aggression, resents being touched, dull behavior, won’t wag tail licking or biting at affected area, lack of grooming Cats: cats can be seen with many of the signs listed above for dogs, and cats are more likely to become extremely grumpy when they are in pain. However, some cats actually purr when they are distressed or in pain! Cats in severe postoperative pain may become aggressive, tearing at the bandage, frantic and vocalizing. Also, cats are more likely to exhibit withdrawn behavior – crouching in the back of the cage, unwilling to use the litter box, etc., than dogs. Table 1 gives you pictorial guides to the way I think animals look when they are normal or abnormal. In each abnormal case, the primary problem may have been pain, but other conditions may also have been present. Please note that after photographing abnormal patients, we attempted to diagnose and treat their distress. Pain scoring systems: Use of behavioral methods to assess pain requires a structured, reliable, valid and recorded system of evaluation and observer training. A pain scale that doesn’t do what it is supposed to do wastes time and is unhelpful to the patients. Visual analog scales (VAS): a line with no markings and a 0 (no pain) and a 100 (worst pain imaginable) at either end. Numeric rating scales (NRS): a number line with discrete numerical markings (as in 1 through 10) which are chosen as a score. Simple descriptive scales (SDS): numerical values assigned to descriptions categorizing different levels of pain intensity (mild, moderate, severe). A pain scale that takes into account the various dimensions of pain is thought to be more useful in indicating how much the pain “meant” to the animal, but VAS, NRS and SDS scales are unidimensional. A pain scale should ideally be multidimensional, in that several aspects of pain intensity & pain related disability are included – especially the dynamic aspects. The composite measurement scale (CMS) is constructed to take into account such dimensions as the temporal patterns, location, interference with basic function, or well-being. There are few validated veterinary CMS pain scales, but this does not mean that scales can’t be crafted, using a basic understanding of pain rating tools and animal behavior, and combining those with actual “in the trenches” experience with observations. Ensure that all potential scale users assign equal meaning / importance to descriptive terms.

Assessment of fear and anxiety: If the animal is vocalizing or struggling, but upon talking to and touching the patient, calming occurs, there is a chance that the problem is less pain and more anxiety. If analgesics have been given and the



animal still vocalizes, and the exam reveals no pain upon palpation, consider giving a trial dose of acepromazine. A dexmedetomidine CRI may also be useful for sedation of overly anxious patients. Often within 30 minutes, the patient is quiet. Dysphoria: This is a special syndrome where opioid treated animals (particularly but not only those treated with pure agonist opioids) appear to be very agitated. It is often mistaken for pain and treated with additional opioid doses. Opioid induced dysphoria is recognized in the human anesthesia/critical care literature. In dogs we see vocalization, panting, and non-responsiveness to human contact and the condition responds dramatically to reversal of the opioid by 0.01 mg/kg naloxone or, in this author’s experience, by 0.1 mg/kg butorphanol (both IV). Response occurs within minutes and the patient becomes oriented to surroundings with more normal behavior. The addition of tranquilizers or sedatives does not permanently resolve the condition. Also, in cats, a dysphoria-like state is observed after surgery on occasion with some opioids. Cats become agitated, develop hyperthermia, and this may also be effectively treated with butorphanol or naloxone reversal (Robertson, 2005). It is important to differentiate true dysphoria from anxiety or pain or discomfort from hyperthermia. Assess for various causes of pain, consider adding a sedative or tranquilizer, and if these do not resolve the issue, then try the antagonist. Animals thus reversed do not appear to be more painful, and “weaker” opioids, +/- adjunctive analgesics can be used to effectively treat pain from then on. You already have a feel for the expected duration of postoperative pain. Severe pain when it is not expected should prompt a look for serious causes, such as infection, pin or screw migration, or pinched nerves. This is one of the most important things to remember. Conclusion: Assessment of pain is a subjective process. Avoid the commonly held notion that a patient who is screaming postoperatively is definitely painful, while the one who is quiet is not. Your patient CAN tell you a lot about how he / she feels, if you take the time to listen AND touch. Suggested Readings: Hansen, B. (2003) Assessment of pain in dogs: veterinary clinical studies. ILAR J. 44, 197- 205 Robertson, S. (2005) Assessment and management of acute pain in cats. J Vet Emerg Crit Care Soc 15(4), 261-272



orientation facial expression posture

Normal

dog

Normal

cat

Abnormal

dog

Abnormal

cat

Very

abnormal

dog

Very

abnormal

cat



SEDATION SCORING FOR SMALL ANIMALS

If the animal is: Score

Standing and/or vocalizing MOST of the time, appears frantic or upset: 0

Sitting, standing or lying down, alert, vocalizing sometimes, watching you with eyes wide open:

1

Sitting, standing or lying down, eyes a bit drowsy, but alert: 2☺

Sitting, standing or lying down, eyes a bit drowsy or squinted, not paying much attention to you unless you enter cage:

3☺

Asleep, but if you call pet’s name, he opens eyes and lifts head - “wakes up” (for deaf animals, gently tap cage door), can lie sternally or sit up:

4☺

Asleep or deeply sedated, when stimulated by touch or voice, opens eyes and lifts head but goes right back to sleep:

5

Cannot rouse patient, even when physically moved: 6

Sedation scoring gives criteria for discussions about patient care ☺means this patient is probably doing well in general Opioids and some other pain medications can cause drowsiness. But so can anesthetics, & other

conditions such as hypoglycemia, hypothermia, shock, and PAIN can make animals appear mentally dull. Patients having a score of 6 (when fully recovered from anesthesia) should be evaluated in case medical treatment is needed.

Patients who vocalize or fret constantly or most of the time may benefit from a walk to urinate, a visit, drugs or techniques to calm them, or may need pain medications. So, if you feel that a patient has a sedation score of 0 or1, it is worth mentioning to the doctor, noting in the record, or walking the patient if indicated.



SURGICAL AND PROCEDURAL PAIN MANAGEMENT


It is common for the veterinarian or technician who is concerned about optimizing pain control to face objections and misconceptions from colleagues. One argument is that animals “need” the presence of acute pain to promote optimal recovery. In general, this is untrue. Other concerns cited include the side effects of certain medications; e.g. immune suppression or ileus, nausea and vomiting from opioids, gastrointestinal ulceration from NSAIDS, tissue toxicity from local anesthetics. Some of these are valid, but knowledge and skill helps avoid them. There are also concerns about pain medications “masking” signs that would alert the clinician or owner to worsening of a condition, such as infection, or tissue destabilization. Generally, astute monitoring means that this is not a concern, but evaluation of the patient is essential. The goal of patient care includes both optimal recovery and comfort but with skill, both can be achieved. One problem is that we often fail to consider that pain itself is detrimental. Acute pain may even be a risk factor for a transition to chronic pain. Acute pain has the potential to be a source of moderate to severe distress to the animal, and to the owner or caregivers. Management efforts must weigh positive and negative effects of pain and its treatment but minimization of pain and stress are major ethical concerns in our responsibility to animals. Causes of and contributions to acute pain: The extent of tissue damage The amount of inflammation The type of tissue damage

o nerve damage causes neuropathic pain o distention, inflammation and necrosis of visceral tissue can cause intense pain o somatic pain is greater when swelling of tissue within fascia or bony confines occurs o ischemia from thrombosis, physical disruption of blood supply to organs is very painful

The individual patient’s tolerance to pain o may be breed or age dependent o may be greatly influenced by fear or anxiety o may also be dependent on the situation – lack of comfortable bedding, familiar people, or

thermal support can increase discomfort Trauma (such as fractures, bruises, burns) can cause more pain than surgery in some cases, because generally, the amount of tissue that is affected is greater. The production of cytokines associated with massive trauma or infection can amplify pain signals. Disease may cause pain. Pancreatitis, gastritis, urinary tract sepsis, pleuritis, inflammatory bowel disease, CNS disease (brain tumors, meningitis/encephalitis) are only some of the many disease states that can be accompanied by moderate to excruciating pain. Urinary tract or gastrointestinal obstruction is very painful. The pain from surgical procedures can also vary depending on the type of surgery, the skill of the surgeon, the amount of tissue handling, and factors such as infection and inflammation. Often, surgical procedures are performed with the purpose of reducing pain (lancing abscess, pulling infected tooth, stabilizing fractures, removing herniated disk) and sufficient pain relief at surgery is needed, in some cases the pain may improve rapidly. One very important type of pain that occurs in patients is that caused by medical procedures themselves. Diagnostic procedures, patient restraint, positioning can be sources of pain in veterinary patients, especially as animals may not be cooperative. Fear of pain can make pain worse. Only surgical pain and procedural pain are amenable to prevention. Other types of pain may have developed to the point of being substantial by the time a patient is seen by the practitioner. Once pain has become established it is thought to be more difficult to overcome. Prevention of surgical or procedural pain involves an attempt to predict the degree of anticipated pain, and to “pre-



treat” with sedatives and analgesics and to minimize iatrogenic damage. For all types of pain, an important concept is that of “multimodal analgesia.” Also important for all types of pain is to consider what can be done to reduce fear, anxiety, physical discomforts such as dry mouth, hunger, thirst, gastric distention, constipation, catabolism, pressure injury, discomfort due to devices, bandages, side effects of medications, and other environmental stressors. Non-pharmacological control of pain and discomfort is as important as use of drugs to reduce pain. Interaction with anesthetics and other drugs: When opioids, local anesthetics, ketamine, or alpha 2 agonists are used prior to or during general anesthesia, the requirement for inhalant and injectable anesthetics can be significantly lessened. It is critical to recognize that reduced doses of anesthetic are needed; extreme anesthetic depth can lead to depression of respiration and cardiac output; risking morbidity or death. Decreased blood flow to the kidney, in combination with NSAID therapy risks nephrotoxicity. Other potential interactions include patients already being treated with psychopharmaceutical drugs, tranquilizers and especially those that impact serotonin levels. It is important to review all therapeutic agents that the patient is receiving in order to maximize safety of acute pain control. Strategies of acute pain treatment: Synergies: For relatively minor pain, a single agent and even as few as one administered dose might be sufficient. Opioid-only, NSAID-only, or local anesthesia-only therapy may be used, depending on the species or situation. Many veterinary clinical pain studies have only evaluated single agent therapy and these may compare drugs of two different types (e.g. buprenorphine versus meloxicam). As the magnitude of pain increases, the necessity for adding a second type of analgesic becomes probable. The opioids, NSAIDS, local anesthetics, ketamine and gabapentin have been shown to have synergistic effects when used in certain combinations. One additional benefit is that usually, the drugs can be used in lower doses than if used alone, and this may reduce the side effects of individual agents. Research supporting analgesic synergies (multimodal analgesia) is common in the human clinical arena and in animal models. And veterinary analgesia clinical trials have also been investigating the impact of adding a second analgesic type. Multimodal analgesia is thus becoming widely appreciated in veterinary medicine. Timing: Dosing of analgesics must mesh with monitoring for pain and observation for side effects. Continuous infusion of certain types of analgesics (opioids, local anesthetics, ketamine, alpha 2 agonists) avoids “peaks and valleys’ in drug levels and may provide better coverage for moderate to severe pain. So, overall, what interventions are possible for acute pain? 1. We can treat pain at a central level Opioids, alpha 2 agonists, and ketamine modify and depress transmission of pain within the CNS To avoid the emotional component of pain, tranquilizers and sedatives decrease anxiety Epidural or spinal analgesics (opioids and local anesthetics) inhibit central pathways as well. NSAIDS given systemically also work centrally (on the brain and spinal cord) to decrease pain. Other drugs such as muscle relaxants, gabapentin, tramadol may have valuable central actions

2. We can target a peripheral aspect, removing the stimulus (injured tissue, foreign body) or use local

anesthetics to block painful stimuli from even entering the spinal cord, and use anti-inflammatory agents such as NSAIDS or corticosteroids to reduce swelling.

3. Lastly, we can use non-pharmacologic methods cold therapy inhibits inflammation and is analgesic acupuncture can give analgesia



nursing care - such as syringing a bit of water onto dry tongues, grooming, attention to noises, drafts, and social contact can affect the patient’s level of distress

Opioids are one of the most common, effective, and safe analgesics currently in use for treating acute surgical, trauma, or medical pain. The type (i.e. agonist-antagonist versus pure agonist) and dose of opioid required are usually chosen based on the expected amount of pain, with pure agonists (morphine, hydromorphone, methadone, fentanyl) chosen for more extensive pain, buprenorphine and agonist antagonists chosen for more moderate pain. When an opioid is chosen from a dose table for a particular animal, it should be kept in mind that additional increments may be needed as one observes the analgesic effect and it is this “total” dose can be given going forward until pain levels decrease.

Administration of an opioid at the time of surgery or after trauma is usually initiated by giving the drug intravenously or intramuscularly, however, oral-transmucosal delivery of buprenorphine in the cat results in rapid and thorough absorption and so this is a potential alternative route for this species. Subcutaneous injection of opioids is becoming recognized as suboptimal in terms of consistency of effect and duration. Opioid analgesia is continued into the postoperative or post-injury period by intermittent dosing or a continuous infusion/delivery method. With intermittent dosing, serum concentrations fluctuate from high to low and the drugs may cease to be effective prior to the next dose, increasing the chances for breakthrough pain. Continuous infusions allow treatment with no drug “troughs”, and can be altered to address needs effectively, but may require additional equipment (e.g. infusion pumps) and monitoring. Epidural morphine has also been demonstrated to provide good analgesia with extended duration in the dog, horse, pig and goat. The duration of opioid treatment depends on the nature of the injury and patient assessment. For most elective surgeries it appears that 24 – 48 hours is common, during which time the doses may be tapered and after which oral medications may suffice. For major traumatic injury, and after more extensive surgeries, longer duration of treatment with opioids may be necessary. Transdermal (TD) fentanyl patches can be used in dogs, & cats. Clinical efficacy data are presently somewhat limited for TD fentanyl. It is important to realize that the lag in onset after patch placement (of 8 – 24 hours), inconsistency of serum levels and thus presumably of effect means that some animals may not experience adequate pain relief. Use of this route must be preceded and/or supplemented by injection, or the patch must be in place prior to surgery. Owners may be instructed to give oral transmucosal buprenorphine in the cat, and potentially in the dog when it is useful to continue opioid therapy in animals treated “at home.” Tramadol, with its opioid-like effect has been prescribed for oral administration in dogs, cats is possibly useful to combine with other oral analgesics for administered by the owner. Concern is often raised about the use of opioids in acute pain patients because of the incidence of undesirable effects such as nausea, constipation and ileus, suppression of cough, respiratory depression and urinary retention. Nausea and vomiting in dogs and cats may occur when non-painful animals are premedicated with pure agonist opioids, but with use of appropriate doses postoperatively, the incidence of vomiting related to opioid dosing is low. When vomiting persists or nausea appears to be present, then reduction of the dose or switch to a “weaker” agonist-antagonist opioid usually resolves the problem. Decreased propulsive bowel motility leading to ileus can be caused by pain, handling of the bowel at surgery, inactivity, lack of oral intake and electrolyte imbalances as well as opioid use. Cough suppression and respiratory depression can be a concern when opioids are used in a patient with pneumonia or blood in the lung secondary to trauma. The reluctance to cough and breathe deeply are also impaired by chest wall or upper abdominal pain, thus there is a need to consider a balanced approach to relief of pain in such patients, using opioids and other analgesics. Animals may experience urinary retention when opioids acting at the mu receptor are used; this may be more profound after epidural morphine. Urinary retention can be treated by partial reversal of mu agonist opioids.



Non-steroidal anti-inflammatory drugs (NSAIDs) are insufficient for moderate to severe pain, but they can be combined with other analgesic drugs. Precautions for use of preoperative NSAIDS must include careful scrutiny of preexisting heath status, monitoring and support of blood pressure. When blood pressure monitoring is not possible, then it is advisable to give NSAIDS to small animals after anesthetic recovery, once a stable state is assured. When no pre-existing or potential risk factors are present, NSAIDS are powerful tools as part of a unimodal or multimodal approach to treating pain. Local anesthetics can be very effective agents for control of acute pain, and are especially useful in combination with other analgesics. There are two main benefits to the use of local anesthetics prior to surgery even when the patient will undergo general anesthesia. These are 1) the ability to reduce general anesthetic doses (thus reducing anesthetic induced cardiovascular depression), and 2) absence of severe pain upon awakening from surgery. All local anesthetic techniques, when used preoperatively, reduce inhalant anesthetic requirements (MAC) from thus the vaporizer setting must be adjusted to avoid excessive anesthetic depth. The duration of local anesthetic action is relatively short, depending on the drug and administration site after many single administration techniques. Thus timing of observations and supplemental treatment with other analgesics when the local anesthetic effect is predicted to wane may be warranted. Intratesticular administration of lidocaine to reduce castration pain is reported for a number of species. Local anesthetic techniques should be in most cases combined with one or more additional analgesic method. Intravenous and intrawound infusion techniques can be used to extend the duration of local anesthetic action. Intravenous lidocaine (IVL) is reported to be beneficial for pain after soft tissue surgery in humans; this has led to extrapolation of its use to veterinary species. Non-surgical types of acute pain (from major trauma, burns and pancreatitis) may also benefit from IVL use. The reduction in hepatic blood flow that occurs during inhalant anesthesia may decrease clearance of lidocaine. Several reports of concentrations and effects of IVL in cats indicate that it should not be used intraoperatively in cats, because of poor ability to metabolize the drug. IVL is routinely used in dogs for surgeries of moderate to severe painful nature, often in combination with parenteral and epidural opioids and ketamine. IVL should be used with caution and possibly lower doses in animals with reduced serum protein levels or poor cardiac output due to increased risk for toxicity; these conditions are common in many critically ill animals. Wound infusion catheters are an emerging new strategy to extend the duration of local anesthesia after surgery. The most studied surgical indication for wound infusion catheters in veterinary medicine is canine total ear canal ablation, but use for extensive soft tissue resection in cats (fibrosarcoma resection) is also reported. Studies reported to date have used either bupivacaine or lidocaine infusion, pain is generally perceived to be adequately managed with low doses of opioids, and complication rates low and not perceived to be problematic. Currently, anecdotal reports are that practitioners are using such wound infusion catheters for limb amputation, ear canal ablation, intercostal and sternal thoracotomy, celiotomy, and major soft tissue tumor excision, in dogs, cats, and ruminants with excellent results and few complications (Abelson et al, 2009). Ketamine is an extensively used component of anesthesia in many animal species. Administration of even very low doses of ketamine reduces the required concentration of inhalant anesthetics required for surgery in dogs, from approximately 20 – 50%. Its anesthetic sparing action may be in part due to an analgesic effect that is present at low and sub-anesthetic dosages. In many species, subanesthetic or so called “low dose”, or “micro dose” ketamine is demonstrated to improve opioid sparing; prevent opioid tolerance; and reduce acute somatic and visceral pain. Because ketamine has a high therapeutic index and is relatively inexpensive, low dose ketamine infusions are now widely used as an analgesic adjunct in dogs & cats for acute pain, even though clinical data to support its efficacy is still needed. Higher anesthetic doses of ketamine are thought to be relatively contraindicated in animals with high intraocular pressures, hypertrophic heart disease, tachyarrhythmias, and in central nervous system disorders, e.g. epilepsy and intracranial surgery. High dose ketamine is avoided in those patients because of its tendency to increase arterial blood pressure and heart rate, and to increase CNS



excitation. Therefore, it may be prudent to avoid low dose ketamine in such patients until evidence of safety is demonstrated. When no contraindications exist, the routine incorporation of intraoperative low dose ketamine for moderate to severe expected pain, or its addition to analgesic regimens represents a safe, inexpensive, and potentially effective technique when current therapy is not deemed sufficient. Low dose ketamine also has potential dose dependent anti-inflammatory actions that may also prove to be beneficial in many critically ill veterinary patients, but more research is needed. Avoid a common source of iatrogenic pain: Older patients are very prone to injury and pain from handling– worsening arthritis pain, muscle pulls, etc. Especially when anesthetized, they are unable to support unstable joints and can wake up from surgery with new pain – caused unnecessarily. Older or very large animals may experience nerve, muscle or joint injury if not properly padded paying special attention to bony areas, or if their position strains ligaments or joints. Muscle and nerve can also be damaged in large patients if a limb hangs halfway off a table edge. Corneal damage can also easily result from mishandling. This can happen during dental procedures when the head of small pets is extensively handled without care in protecting the eyes. The transition to “go home meds”: stopping injectable medication in the hospital just before the patient is discharged may result in the sudden development of pain upon reaching home. It may not be noticed right away as the patient is usually going to be “happy” to be at home with familiar friends, as well as potentially exhausted from the experience of being hospitalized. It may be advisable to taper the injectable drugs some time before discharge, and to institute oral analgesics at that point. Fentanyl patches must be placed in dogs at least 12 and preferably 24 hours before discontinuation of injectable drugs and in cats, 6 – 8 hours before discontinuation. Have an idea of how much pain should occur and how long pain should last - this will allow you to spot unusually severe pain. Unusual amounts of pain may signal that an infection, instability or nerve entrapment are present, in which case a careful examination should take place. The treatment for pain due to an “acute abdomen” (caused by severe abdominal disease that may pose a serious risk to the patient’s life) is not simply to give pain medications. The morning after abdominal surgery (GDV), a dog who demonstrates depression, panting, a heart rate of 200 and cranial abdominal “splinting” is not showing the ordinary signs of a dog 24 hours post GDV surgery. This is a dog in early shock from dehiscience of a gastric repair, and has a problem that will lead to his death if the abnormality isn’t spotted and addressed.



Drug Dose Duration Species Route Comments

Buprenorphine 0.0005 - 0.03 mg/kg

4 - 8 hr

both

IV, IM, OTM*

Partial mu agonist. For more severe pain, choose pure agonist opioid. Use lowest dose only for animals < 8 weeks of age, or with very mild pain. New information suggests use of 0.02 mg/kg in dogs and cats for surgery such as OHEa,b. Higher doses have been used when assessment indicates need. Also, duration may be shorter than previously reported, unless doses higher than 0.01 mg/kg are usedb. Onset more rapid with IV or OTM (cat) usec. OTM route well established in cat, may be feasible (but less bioavailable) in the dogd

Butorphanol 0.1 - 0.4 mg/kg 1 - 4 hr both IV, IM, SC Use only for mild pain, or at 0.1mg/kg IV to treat/diagnose dysphoria or urinary retention. Sedative/analgesic effects useful in combination with acepromazine, dexmedetomidine, benzodiazepines for premedication.

Fentanyl 2- 10 mcg/kg

10 -30 mcg/kg/hr

2 - 10 mcg/kg/hr

15 min

intraop

postop

both

both

both

IV bolus

IV CRI

IV CRI

Pure agonist with short onset and recovery time useful for critically ill patients, or those with very severe pain. In awake patient, titrate loading dose to effect while monitoring respiration. Anesthetized patients receiving fentanyl bolus and CRI generally require assisted ventilation and may require anticholinergic administration if bradycardia- induced hypotension ensues.

Fentanyl patch 2 – 4 mcg/kg/hr 3 days dog Trans dermal

Onset of clinical effect 12 – 24 hrs in dog, 6 – 12 hrs in cat, must use injectable opioid until this occurs. Also, individual variation means may be insufficient for pain. Heating of skin over patch risks excessive levels. In animals < 6 – 10 kg, may remove only half the backing to expose smaller surface to skin, unless 12.5 mcg/hr patch is available. 25 mcg/hr patch 3 – 5 days cat Trans

dermal

Hydro-morphone

0.05 – 0.2 mg/kg 2 – 6 hr both IV, IM Pure agonist good for treatment of moderate to severe pain. In cats, monitor for hyperthermia and use lower dose if possible. SC dosing gives suboptimal serum levels, but can be usedc.

Morphine 0.5 - 2 mg/kg 0.1 - 0.5 0.05 - 0.2 mg/kg/hr 0.1 mg/kg

1 - 4 hr 3 - 6 hr NA 8 – 24 h

dog cat dog both

IV, IM, SC IV, IM, SC IV CRI LS epidural

Pure agonist good for treatment of moderate to severe pain. IV administration may cause histamine release unless very slow administration, but IV CRI commonly used safely. Cats may not make active metabolite, thus higher doses or different opioid may be more suitable. Use preservative free morphine or dilute with preservative free saline to 0.2 ml/kg (dog) or 0.3 ml/kg (cat). Provides analgesia as far forward as thorax and forelimb. Add 1 mg/kg bupivacaine in dog to prolong analgesia significantly.f (Maximum 6 ml volume in dog)

Naloxone 0.005 – 0.04 mg/kg

15-30 min both IV Antagonist to have on hand in case of need to reverse pure agonist opioids. Will not reverse buprenorphine. Start at very low doses unless emergent condition exists.

Oxymorphone 0.05 – 0.1 2 - 6 hr both IV, IM, SC

Pure agonist opioid good for treatment of moderate to severe pain.

Tramadol 3- 5 mg/kg 2 -3 mg/kg

6 - 12 hr 8-12 hr

dog cat

PO PO

Non-opioid analgesic drug with mu agonist like action, and other actions. Unreliable as monotherapy, combine with NSAID or other analgesic. Not controlled. Dysphoria in cat may limit dose range. Avoid in animals taking drugs that elevate serotonin levels (antidepressants, seligilene). Oral tablets may be useful for dispensing, but are bitter and aversive to many animals.



Drug Dose Comments

Acepromazine IV, SC, IM: 0.01 - 0.025 mg/kg Not analgesic although may enhance analgesia and reduce anxiety when combined with other drugs. Onset after IV route most rapid, but full onset after injection by any route may take up to 30 minutes. Potentiates sedative properties of some analgesics. Avoid in hemodynamically unstable patients. Use lower doses in sighthounds, giant breeds, MDR1 deficient dogs/breeds, and markedly brachycephalic animals.

Dexmedetomidine IV bolus: 0.5 – 5.0 mcg/kg “to effect” IV CRI: 0.5 – 3.0 mcg/kg/hr

Sedative, analgesic, anxiolytic, reversible useful in combination with other analgesics. Sedation is dose dependent and can be adjusted by altering CRI. A 1mcg/kg bolus + 1 mcg/kg/hr IV CRI studied in healthy dogs. OTM delivery of 20 – 40 mcg/kg in cat is as bioavailable as IV route, may be useful for bolus micro-dosesa

Gabapentin PO: 2 – 10 mg/kg q 8 - 12 hr Potentiates sedative properties of some analgesics. Author recommends starting with 5 mg/kg q 12 hr in more robust patients, lower in critically ill or elderly.

Ketamine IV CRI 0.1 - 0.6 mg/kg/hr Ketamine may be contraindicated with severe CNS disorders, in presence of unstable tachyarrhythmias, glaucoma, and cats with hypertrophic heart disease. Reduce dose if tremors or agitation occur.

Lidocaine (dog) IV bolus for extreme pain: 2 mg/kg IV CRI: 30 - 50 mcg/kg/hr

Do not use by IV infusion in cats until additional information on safety is available. Critically ill animals w/ hypoproteinemia and acidosis are more prone to lidocaine toxicity.



USE OF LOCAL ANESTHETICS FOR PERIOPERATIVE AND PROCEDURAL PAIN CONTROL: INTRAVENOUS AND INTRA-WOUND LOCAL ANESTHESIA


Traditional nerve block techniques eliminate the pain of surgery but mastery can require significant expertise. In addition, the two commonly used local anesthetics have relatively short durations (lidocaine, 1 – 2 hours, bupivacaine 4 – 6 hours). There are two methods by which long duration analgesia using local anesthetics can be achieved: 1) intravenous infusion of lidocaine, and 2) the use of intra-wound infusion devices. Local anesthetics are not just useful to desensitize tissues for a period of time. They have been shown to have broad anti-inflammatory effects, including inhibition of leukocyte function, reduced production of eicosanoids, thromboxane, leukotriene, histamine, and inflammatory cytokines, and enhanced scavenging of oxygen free radicals. These effects are proposed to explain the effect of local anesthetics to inhibit edema formation in various conditions, reduce acute lung injury and improve survival in sepsis models. Lastly, they may have antimicrobial, antifungal and antiviral effects (Cassuto et al 2006). Vital though it is in the overall immune response, inflammation can be responsible for severe morbidity in patients, in addition to its impact on the generation and maintenance of pain. When used appropriately, the “less local” techniques of intravenous and intra-wound administration of local anesthetics may be regarded as having multiple beneficial effects: on pain, on inflammation, and as a bonus, perhaps even on survival.

Intravenous infusion: IV lidocaine (IVL) has been shown to have anti-hyperalgesic effects in human and animal models of incisional, burn, visceral, thermal and mechanical stimulus (Ness, 2000, Robertson et al, 2005). The mechanisms by which IVL produces its analgesic, anti-hyperalgesic, and anti-inflammatory effects include: sodium channel blockade, and inhibition of both GPC receptors and NMDA receptors (Kaba et al, 2007).

Human studies have established benefits for pain control in soft tissue surgeries. For example, an intraoperative infusion of lidocaine ending at 1 hour after surgery resulted in lower pain scores during movement and less morphine consumption for 72 hours (Koppert et al 2004). Kaba et al (2007) demonstrated multiple beneficial aspects of IVL in a study of human colectomy surgery patients; significant reductions in time to return of bowel function and length of hospital stay as well as pain, opioid consumption and fatigue scores occurred with use of a 24 hour infusion. In addition, IVL treated patients had a 35% reduction in inhalant anesthetic (MAC reduction) and reduced intraoperative opioid requirements. IVL may be a promising therapy for pain and minimization of tissue damage in burn patients (Mattssona et al, 2000). And in a recent meta-analysis involving 706 patients, IVL was able to cause short term alleviation of neuropathic pain of various origins. (Tremont-Lukats et al, 2005). However, a study of IVL during hip replacement surgery in humans did not show a benefit of lidocaine (Martin et al, 2008). In veterinary patients, a rather compelling case can be made for the use of perioperative IVL for pain control in a variety of surgical procedures, with the added benefit of MAC reduction. Extrapolating from human data, it is less clear whether the same is true for orthopedic or other types of surgeries. However, because of the potential to reduce neuropathic and visceral pain, it may be possible that orthopedic, neurosurgical and acute disease states (e.g. pancreatitis) as well as trauma pain, could stand to benefit from the use of IVL. This is especially true if the technique could provide opioid sparing and other (e.g. antimicrobial, anti-inflammatory) effects. Caution is needed in avoiding toxicity, as the reduction in hepatic blood flow that occurs during inhalant anesthesia may decrease clearance of lidocaine, leading to serum concentrations outside of the safe range. This has been shown to be the case in the cat but not in the dog (Thomasy et al, 2005). At our teaching hospital, we routinely use perioperative IVL in the dog for any surgery of moderate to severe painful nature; only in certain cases is it continued



postoperatively. Although we recommend it as a safe and sparing adjunct to opioid and other analgesics for surgery, trauma, and pancreatitis at a dose of 50 mcg/kg/min, we have no actual data to support its benefit. Good quality studies are clearly needed. We have seen few complications after using it in thousands or canine cases. We do not use IVL in cats, due to a concern about toxicity (Robertson, 2005). Intrawound sustained local anesthesia – the “wound soaker catheter”: One of the past decade’s remarkable advances in managing the pain of major surgery involves local anesthetic delivery to the wound and is easily adopted for use in veterinary patients. The availability of implantable infusion catheters has made it possible to use repeated or continuous infusion of local anesthetics into surgical wounds to prolong the duration of pain control. FDA approved human use catheters are available, but costly. Two modestly priced types are commercially available for veterinary use (see below). Basically they consist of a pliable catheter with tiny holes along the implanted end; functioning somewhat like a garden “soaker hose.” The catheter is buried in the wound bed during surgical closure. Constant infusion of the drug is maintained by fluid or syringe pump for patients staying in hospital for 36 hours or longer. If electronic pumps are unavailable, or if early discharge is planned, an elastomeric balloon pump can be used to achieve continuous infusion. If neither is available, it is possible to use intermittent manual injection of bupivacaine every 4 – 6 hours. In humans, these “wound soaker” or wound infusion catheters are used for cardiothoracic, abdominal, amputation and mastectomy surgeries, as well as for other major surgery types. Placement of the catheter is generally done at the end of surgery, buried in the deepest layer of wound and infusion duration can range from 1 hour to 2 days. Benefits include reduction of mean pain scores at rest and with activity, reduction of daily consumption of opioids, and trends towards better patient satisfaction and reduced length of hospital stay. To date, a small number of veterinary clinical studies of wound soaker catheters have been reported in the literature. The most studied surgical indication was total ear canal ablation in dogs, but use for extensive soft tissue resection in cats (fibrosarcoma resection) is also reported. Our investigators have published a review of clinical use of wound soaker catheters in our hospitals (see below). Collectively, the studies reported to date have used either bupivacaine or lidocaine infusion. As with human studies, pain control was optimized, there was a lower need for strong opioids and low complication rate. Ancillary benefits include reduction in the level of sedation or opioid side effects and reduced hospital stay. Those of us who were taught that local anesthetics impair wound healing and can lead to infection might be skeptical about adopting the wound infusion techniques. Indeed, there are tissue injury animal models for bupivacaine (Zink et al, 2005). However, reported clinical complication rates for various methods of wound infusion of local anesthetic techniques in humans are extremely low, with the exception of direct constant infusion into joints (which is not recommended currently). In addition, our substantial experience with use of wound infusion techniques has won broad support with our surgeons and some referring veterinarians, who request the use of this technique, particularly for limb amputations. If you perform thoracotomies, limb amputations or extensive soft tissue resections, it is worth your time to look closely at the use of peripheral local anesthetics and to explore their usefulness in your pain medicine. Specific instructions for use of wound soaker catheters: Pre- intra- and post - operative analgesics are administered – preferably including a strong opioid

+/- other adjunctive pain medications, tapering to oral “go home” medications. Pain is assessed at regular intervals.



Prior to surgical closure, a soaker catheter is chosen so that the infusion length will span the long axis of, but remain within the wound. It is placed in the deepest layer of the wound, ideally so that the injection port exits more dorsally and to be close to major nerve trunks.

The wound is closed over the catheter and it is fastened to the skin where it exits by means of a waterproof tape butterfly or other knotted suture technique. Care is taken not to occlude the soft catheter.

A priming dose of bupivacaine (1.0 - 1.5 mg/kg) is injected slowly prior to discontinuing anesthesia. Local anesthetic presence in the wound is continued by either:

o Intermittent injection of bupivacaine over 2 minutes (dog or cat) o Continuous infusion of lidocaine (dog only) (may result in spotty delivery)

Administration of local anesthetic is continued for at least 24 hours, and up to 3 days. After the last dose of local anesthetic, wait for 6 or more hours to ensure that pain does not recur. Then, remove fastening sutures and pull the wound soaker catheter.

Dosing: o Dogs – lidocaine continuous infusion rates of 2.0 mg/kg/hour, and the dilution of lidocaine

(from 1 – 2%), adjusted so that the following approximate volumes are used: 30 – 40 kg, limb amputation wound: 3 - 4 mls/hour 5 – 25 kg, limb amputation wound: 1 – 3 mls/hour 30 – 40 kg, thoracotomy wound: 2 – 3 mls/hour 5 – 25 kg, thoracotomy wound: 0.75 – 2 mls/hour

o Dogs – bupivacaine diluted to 0.25% with saline, intermittent injection every 6 hours: 30 – 40 kg, limb amputation wound: 4 – 8 mls/dose 5 – 25 kg, limb amputation wound: 1.5 – 6 mls/dose 30 – 40 kg, thoracotomy wound: 2 – 3.5 mls/dose 5 – 25 kg, thoracotomy wound: 0.75 – 2 mls/dose

o Cats - intermittent bupivacaine diluted to 0.25% with injection of 0.5 mg/kg every 4 – 6 hours.

The volume of drug used may be adjusted somewhat according to the size of the wound bed and adequacy of pain control. Palpation of the entire wound, initially with the amount of pressure that you can comfortably apply over a closed eyelid and then slightly more, should elicit little reaction from the patient. Technical staff should be trained and the catheter hub, syringes, pumps and any lines should be clearly marked to prevent accidental intravenous injection of local anesthetic – a significant hazard.

Sources of catheters: o http://milainternational.com/us/products/small-animals/pain-management/diffusion-

catheter-wound-catheter.html o http://www.recathco.com/staging/catheters/Post-Op.html

Case Example: An 8-year-old, male neutered, 30 kg, mixed breed dog presents with recent onset of left hind leg lameness. Radiographs and subsequent biopsy reveal presence of an osteosarcoma of the distal femur. The decision to amputate the limb is made. Limb amputation causes severe pain that is best managed by a multimodal analgesic strategy in the perioperative period and continuing for up to several weeks after surgery. The dog is premedicated with acepromazine, 0.02 mg/kg, hydromorphone 0.1 mg/kg. After induction of anesthesia, a lumbosacral epidural with 0.1 mg/kg preservative-free morphine is placed. Prior to closure of the wound, a wound soaker catheter with a diffusion area of 4 – 5 inches is placed in the deepest fascial layer of the wound, exiting towards the dorsal rump region and secured. After wound closure, a dose of 9 mls of 0.5% bupivacaine ([30 kg X 1.5 mg/kg]/5 mg/ml) is injected through the catheter. Postoperatively he is given a 2.2 mg/kg dose of carprofen SQ. Within 3 hours of anesthetic recovery, a continuous infusion of

http://milainternational.com/us/products/small-animals/pain-management/diffusion-catheter-wound-catheter.html

http://milainternational.com/us/products/small-animals/pain-management/diffusion-catheter-wound-catheter.html

http://www.recathco.com/staging/catheters/Post-Op.html



lidocaine through the wound soaker is started. His now lower bodyweight is estimated at 27 kg. The ideal volume for this size patient and wound is approximately 3 mls/hour, which at 2 mg/kg/hour is 2.7 mls per hour of 2% (20 mg/ml) lidocaine. Using a syringe pump, the lidocaine is delivered to the wound for a total of 36 hours. During this time, intermittent IV injections of buprenorphine (0.01 – 0.02 mg/kg q 6 hours) or hydromorphone (0.05 – 0.1 mg/kg, q 6 hours) are given, increasing the interval between opioid doses as his pain assessments indicate. The dog may be discharged on oral carprofen plus tramadol +/- gabapentin, continuing for as much as 2 weeks. References: Abelson, A (2009) Characterization of the use of a wound soaker catheter to deliver peripheral local anesthetic: 56 cases. Vet Anes Analg Cassuto et al (2006) Anti-inflammatory properties of local anesthetics and their present and potential clinical implications. Acta Anaesthesiol Scand 50: 265—282 Davis KM, et al (2007b) Correlation between perioperative factors and successful outcome in fibrosarcoma resection in cats. Vet Rec 161: 199-200,. Kaba, A et al (2007) Intravenous lidocaine infusion facilitates acute rehabilitation after laparoscopic colectomy. Anesthesiology 106:11–8 Koppert et al (2004) Perioperative intravenous lidocaine has preventive effects on postoperative pain and morphine consumption after major abdominal surgery. Anesth Analg 98:1050 –5) Liu, SS et al (2006) Efficacy of continuous wound catheters delivering local anesthetic for postoperative analgesia: a quantitative and qualitative systematic review of randomized controlled trials. J Am Coll Surg 203: 914-932. Martin, F et al (2008) Lack of impact of intravenous lidocaine on analgesia, functional recovery, and nociceptive pain threshold after total hip arthroplasty. Anesthesiol 109:118–23 Mattssona, U et al. (2000) Intravenous lidocaine infusion in the treatment of experimental human skin burns -digital colour image analysis of erythema development. Burns 26 710-715 Radlinsky MG et al (2005) Use of continuous, local infusion of bupivacaine for post-operative analgesia in dogs undergoing total ear canal ablation. JAVMA 227: 414-419. Robertson,SA. (2005)Assessment and management of acute pain in cats J Vet Emerg Crit Care 15(4) 261-272 Thomasy, SM et al (2005) Pharmacokinetics of lidocaine and its active metabolite, monoethylglycinexylidide, after intravenous administration of lidocaine to awake and isoflurane-anesthetized cats. AJVR 66:1162–1166 Tremont-Lukats IW et al (2005) Systemic administration of local anesthetics to relieve neuropathic pain: a systematic review and meta-analysis. Anesth Analg 101:1738 –49 Wolfe TM, et al (2006). Evaluation of a local anesthetic delivery system for the postoperative analgesic management of total ear canal ablation- a randomized, controlled, double-blinded study. Vet Anaes Analg 33: 328-339. Zink,W et al (2005)The long term myotoxic effects of bupivacaine and ropivacaine after continuous peripheral nerve block. Anesth Analg 101:548 –54

A.Z Karas DVM, DACVA Doses based on author’s experience. 2013 Tufts VETS

Many Ways to Work Magic on Kitties

Physical condition:

Temperament: Sedation needs: (note, if using oxymorphone in cats, can partially reverse w/ 0.1 mg/kg butorphanol IV if hyperthermia or dysphoric post procedure)

Minor (suture removal etc) Moderate (premed, xrays,, bandage change Strong(painful things, minor surgery, biopsy)

Normal healthy young (3 mo) to middle aged (11 y) cat with NO heart murmur:

Social manners +/- nervous

Butorphanol 0.2 – 0.3 mg/kg

“KBAG” ketamine 5 mg/kg + BAG

Buprenorphine 0.02 mg/kg + ace +/- ketamine 2 mg/kg

Oxymorphone 0.1 mg/kg + ace +/- glycopyrrolate

Oxymorphone 0.1 mg/kg + ace +/- Ketamine 2 - 7 mg/kg

Buprenorphine 0.02 mg/kg + ace +/- ketamine 2- 7 mg/kg

Butorphanol 0.2 mg/kg + dexdomitor 0.01 mg/kg +/- ketamine 2.0 mg/kg

Not a happy camper (also probably nervous)

“KBAG” ketamine 5 – 7 mg/kg + BAG

Butorphanol 0.2 mg/kg + dexdomitor 0.01 mg/kg +/- ketamine 2 mg/kg

Ketamine 5 mg/kg + Oxymorphone 0.1 mg/kg + ace

Buprenorphine 0.01 mg/kg + dexdomitor 0.01 mg/kg +/- ketamine 2– 7 mg/kg

Young to middle aged cat with stable heart murmur or gallop: (avoid ketamine and dexdomitor)


Butorphanol 0.2 – 0.3 mg/kg

Add ace 0.025 mg/kg or midazolam 0.2 mg/kg

Buprenorphine 0.01 – 0.03 mg/kg + ace OR midazolam 0.2 mg/kg

Oxymorphone 0.1 mg/kg + ace OR midazolam 0.2 mg/kg

(to above add glyco 0.01 mg/kg IM or IV if anesthetized HR < 90 with hypotension (BP < 70)) (Midazolam may make some stable cats ballistic)


Butorphanol 0.2 – 0.3 mg/kg + ace 0.025 mg/kg might possibly help not certain

Buprenorphine 0.01 – 0.03 mg/kg + ace

Oxymorphone 0.1 mg/kg + ace (Midazolam may make some stable cats ballistic)

May need to use chamber inhalant induction if insufficient.

(to above add glyco 0.01 mg/kg IM or IV if anesthetized HR < 90 with hypotension (BP < 70))

Fragile, elderly or systemically ill (CKD,AKI, trauma, sepsis, hepatic/biliary dz, etc).


Butorphanol 0.2 – 0.3 mg/kg IM + midazolam 0.2 mg/kg

Buprenorphine (esp. w/ pain present / avoid in unstable patients) 0.01 – 0.02 mg/kg +/- low dose ace

Oxymorphone 0.0 5 – 0.1 mg/kg + midazolam 0.2 mg/kg OR low dose ace

(Midazolam may make stable but grumpy cats ballistic)

May need to use chamber inhalant induction if insufficient.

(to above add glyco 0.01 mg/kg IM or IV if anesthestized HR < 90 with hypotension (BP < 70))


See entry to right Chamber induction is often useful alone.

Kitten < 12 weeks


Butorphanol 0.2 mg/kg Buprenorphine (esp. w/ pain present / avoid in unstable patients) 0.01 – 0.02 mg/kg +/- low dose ace

Oxymorphone 0.0 5 – 0.1 mg/kg + midazolam 0.2 mg/kg OR low dose ace

Feral/ wild thing “KBAG” ketamine 5 – 7 mg/kg + BAG

Oxymorphone 0.05 – 0.1 mg/kg + low dose ace +/- Ketamine 2 - 7 mg/kg

Buprenorphine 0.01 mg/kg +low dose ace +/- ketamine 2- 7 mg/kg

BAG = butorphanol 0.2 mg/kg, ace 0.05 mg/kg, glycopyrrolate 0.01 mg/kg IM (give half of this mixture when using IV administration)

Acepromazine doses: base on age, condition and route: 0.05 mg/kg < 8 y, 0.025 mg/kg for 8 – 12 y, 0.01 mg/kg > 12 y. Ace takes 30 minutes for full onset, no matter how you give it. Can be given OTM (squirt in mouth) prior to using other sedatives. If given IV, use half the above doses. Ace alone is not sedative in cats but can calm them (hospitalization, pre and post op). “Low dose ace” is half or less than indicated for young cat.

Dexdomitor in cats: if cat is to stay in clinic for > 1 hour after sedation and is painful or grumpy, then resist the temptation to reverse with atipamezole, let kitty sleep it off. Also if use higher doses of ketamine (> 5 mg/kg). Avoid dexdomitor in cats w heart murmurs.

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Procedural Pain Management

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Chicago Veterinary Medical Association - June 12, 2013

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Alicia Z. Karas MS, DVM, DACVA

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Guide to use of peri-anesthetic anticholinergics (dogs and cats)

Favors “do not

use”

Favors “yes, use”

Baseline HR high?*

YES NO

Potential for trigemino-cardiac reflex? (ocular,

dental, facial pain)

Is high vagal tone inherantly likely in this

patient? (brachycephalic, pediatric, small white breed, mini schnauzer,

dachshund).

NO YES

YES NO

Will ketamine be used?

NO YES Does patient have

cardiac dysfunction or tachyarrhythmias?

YES (avoid

initially)

NO (fine to

use) Karas, AZ. Tufts Cummings School of Veterinary Medicine, 2013

Glycopyrrolate: 0.01 mg/kg IV, IM, SQ Atropine

0.02 mg/kg IV, IM, SQ

NEVER give < ½ dose of anti-cholinergics may cause bradycardia. Also, IM and SQ dosing in anesthetized patients may cause AV block initially until reaches full onset.

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Checklist for Anesthesia and Surgery *** Initial each step: patient label here Date of procedure _________

For workup and before giving premed: _____ Medications, when last given, recorded on anesthesia request?

_____ Review FIRST & paper med records for relevant info including previous anesthesia history?

_____ Confirmed surgery site with surgeon?

_____ TPR & temperament/pain eval, weight, performed & recorded on Tx sheet and anesthesia request??

_____ Attending DVM approval of workup?

Before induction: _____ Has the anesthetist reviewed anesthetic & treatment plan?

_____ Preoperative met check or other diagnostic procedures performed?

_____ Anesthesia machine pre-use check performed?

_____ OR set up, packs, towels, drapes, light handles, heating pad, anesthesia machine?

_____ Antibiotics, fluids, blood products, other drug therapies (CRI) ready to be given?

_____ Check HR prior to induction?

_____ Are post-operative radiographs needed? If so coordinate with radiology tech.

Before surgery: _____ Site/surgery confirmed?

_____ Antibiotics given?

Before recovery: _____ Sponge count? Biopsy specimens in jars and labeled?

_____ Postoperative treatment orders written/initialed by attending Dr.?

_____ Bladder emptied (when feasible) prior to recovery?

_____ E collar, catheter extension/taping ready, etc?

After recovery: _____ Post anesthesia status performed & recorded (TPR, pain, anxiety?)

_____ Rounded with ER technician?

_____ Controlled drug check performed? Tvetsurgery_v.1_3-1-12



Post anesthesia temperature support monitoring:

Temp at end of anesthesia

Thermal support

measures Monitoring Comments

≤ 96 F HW heating pad

PLUS Bair Hugger

Temp check q 30 minutes until > 98/99 on heat, then remove heat and check temp for 1 – 2 more hours to ensure that temp doesn’t decrease below 98 . These patients are unstable and you should stay with them until they are > 96 F.

Patients who have difficulty with oxygen delivery (heart failure, pulmonary disease, anemia) will shiver when cold and this makes their O2 demand increase by 200% OR MORE. Thus preventing shivering by waking them up after warming them is often a desirable goal. It seems counter-intuitive, but actually may be safer.

> 96 F but

< 99 F HW heating pad

Temp check q 1 hour until > 99 F OR until pet is too active or resentful for you to temp

Patients on opioids will often not have core body temperatures higher than 98 F (the opioids make them think they are too hot, and the brain orders the body to cool off). Therefore, temperature checks every hour when the patient is alert, functioning, and mentally oriented only serve to annoy the patient. Thus if the patient looks alert but has a temp of 98 or 99 , then it is safe to DC hourly temp checks and just monitor their TPR daily and their attitude every 4 – 6 hours.

≥ 103 F

Move blankets

away from half

of cage floor.

Temp check q 1 hour, if rises to 105 F,

then take measures to treat

hyperthermia

This is most often a problem in cats on pure agonist opioids, and occasionally buprenorphine or ketamine. Methods to treat opioid – related hyperthermia include: provide cool surface, dampen paws and ears, give cool SQ fluids, give small dose of acepromazine, give 0.1 mg/kg butorphanol IV, switch to a “lesser” opioid (i.e. buprenorphine).

Note: 1. Small patients whose cages are entirely lined with a heating pad can get too hot quickly and then be miserable and harmed by

heat stress. When possible, leave room for the patient to get off the heating pad and if you see a patient on heat who is standing up, or struggling, check to make sure they aren’t too hot.

2. Also, using isopropanol alcohol on pads does help patients cool off but it tastes awful! Maybe ice packs in cage would be less noxious.

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