anesthetic problems and emergencies

ANESTHETIC PROBLEMS

AND EMERGENCIES

CHAPTER 12

Every anesthetic procedure has the potential to cause

death of the animal

Emergencies are uncommon and the overwhelming majority of

patients recover from anesthesia with no ill lasting effects

WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?

1. HUMAN ERROR!

HUMAN ERROR FAILURE TO OBTAIN AN ADEQUATE

HISTORY OR PHYSICAL EXAMINATION ON THE PATIENT.*Ideally, every patient scheduled for

anesthesia should have a complete physical examination, and a thorough history should be obtained with the owner present.

Less than ideal circumstances are common: Owner drops patient off in a hurry Patient brought in by neighbor or friend Receptionist takes the history Physical exam is cursory or omitted

HISTORY?

PHYSICAL?

HUMAN ERROR LACK OF FAMILIARITY WITH THE

ANESTHETIC MACHINE OR DRUGS USED

The confident, knowledgeable, experiencedRVT!

The not so confident kennel worker who wasasked to assist in surgery today.

HUMAN ERROR

INCORRECT ADMINISTRATION OF DRUGS INACCURATE WEIGHT MATHEMATICAL ERRORS USE OF WRONG MEDICATION

*Be aware of medications that come in different concentrations

ADMINISTRATION OF MEDS BY INCORRECT ROUTE*knowledge of pharmacology*drugs with narrow margin of safety

CONFUSION BETWEEN SYRINGES*ALWAYS LABEL SYRINGES

USE OF INAPPROPRIATE SYRINGE SIZE

HUMAN ERROR

PRESSURES AND DISTRACTIONS Feeling hurried or rushed Distraction because of ineffective multi-

tasking Fatigue Inattentiveness

Be proactive, rather than reactive! Recognize early signs of trouble Pay attention to patient and machines


2. EQUIPMENT FAILURE

*In many cases the failure of the machine is in fact a failure of the operator.

EQUIPMENT FAILURE

CO2 ABSORBER EXHAUSTION *In re-breathing systems, if CO2 is not

removed from the circuit, the patient will experience hypercapnia.* In a non re-breathing system, if the gas flow is too low, there may also be a significant re-breathing of expired gases.

↑ CO2 = Tachypnea, tachycardia, brick red mucous membranes, cardiac arrhythmias, respiratory acidosis

Human error!

EQUIPMENT FAILURE INSUFFICIENT O2 FLOW

You will need to check both the flowmeter and the oxygen tank pressure gauge.

Oxygen tank runs out Hose becomes disconnected Obstruction or leak occurs*If the oxygen flow stops while the patient is hooked up to a

non re-breathing system, the anesthetist should disconnect the hose from the Endotracheal tube, allowing the patient to breathe room air.

• If a re-breathing (circle) system is being used, the patient can remain connected for a short period of time, provided the reservoir bag remains inflated.

Human Error

EQUIPMENT FAILURE

ANESTHETIC MACHINE MISASSEMBLEDTake time to learn and follow the

direction and path of gas flow within the machine. Every time a connection is added or removed, the anesthetist should ensure that the correct pattern of flow is maintained and that all connections are secure.

**Soda-Lyme container main leak

EQUIPMENT FAILURE ENDOTRACHEAL TUBE PROBLEMS

BLOCKED TUBES Twisting or kinking of the tube (inappropriate

positioning) Accumulation of material such as blood, saliva,

excess lubricant Tube advanced too far into a bronchus

CHECK TUBE FUNCTION: BAG the patient – watch for chest rising Disconnect the patient – feel for air coming out of

the tube when the patient’s chest is compressedIf an accumulation of material is causing the obstruction, it

may be helpful to suction with a syringe through a red-rubber catheter or feeding tube.

EQUIPMENT FAILURE

VAPORIZER PROBLEMS Wrong anesthetic in the vaporizer Vaporizer is empty Do not tip the vaporizer – could result

in leakage into the oxygen bypass Vaporizer dial may be jammed Don’t overfill the vaporizer

EQUIPMENT FAILURE

POP-OFF VALVE PROBLEMS The pop-off valve is inadvertently left closed Closed pop-off valve →pressure rises in the

circuit →reservoir bag expands, as well as the patient’s lungs →exhalation is prevented

*This can lead to decreased cardiac output, low blood pressure, and death.

If pressure rises in the circuit and the bag is full and tight, the anesthetist should attempt to open the pop-off valve and/or decrease the oxygen flow rate.


3. ANESTHETIC AGENTS

Every injectable or inhalation agent has the potential to harm a patient and, in some cases, cause death. Review the description of the pharmacologic and physiologic effects of pre-anesthetic and general anesthetic agents in chapters 1 and 3.


4. PATIENT FACTORS

PATIENT FACTORS

GERIATRIC PATIENTS (75% of life expectancy)

POTENTIAL PROBLEMS Reduced organ function- liver, kidney, heart Poor response to stress At risk for degenerative disorders- diabetes,

CHF, cancer Increased risk for hypothermia and

overhydration Prolonged recovery

Geriatric Patients solutions

POTENTIAL SOLUTIONS Reduce anesthetic dosages Increase preanesthetic blood work

from mini to a general profile, include u/a, x-rays, ECG if needed

Allow a longer time for response to drugs

Reduce fluid rate Keep patient warm Choose anesthetic agents with

minimal CV effects Pre-oxygenate

PATIENT FACTORS PEDIATRIC PATIENTS (<3 months)

POTENTIAL PROBLEMS Increased risk for hypothermia and overhydration Increased risk of hypoglycemia, hypotension, Bradycardia Inefficient excretion of drugs-reduced kidney and liver

function Difficult intubation Difficult IV cath placement

POTENTIAL SOLUTIONS Be proactive about heat preservation Avoid prolonged fasting (+/- 5% dextrose administration) Reduce anesthetic dosages Use a gram scale to weigh Use inhalant anesthetics

PATIENT FACTORS BRACHYCEPHALIC DOGS

POTENTIAL PROBLEMS Conformational tendency toward airway obstruction

Elongated soft palate Small nasal openings Hypoplastic trachea Difficult to intubate

Abnormally high vagal tone Bradycardia

POTENTIAL SOLUTIONS Use an anticholinergic Pre-oxygenate Induce rapidly with IV agents Delay extubation Close monitoring during recovery- recover in a

excitement free area

PATIENT FACTORS

SIGHTHOUNDS POTENTIAL PROBLEMS

Increased sensitivity to barbiturates Lack of body fat for redistribution/elimination

of the drug POTENTIAL SOLUTIONS

Use alternative agents

PATIENT FACTORS OBESE PATIENTS

POTENTIAL PROBLEMS Accurate dosing is difficult- lower dose /kg Poor distribution of drugs Respiratory difficulty- shallow rapid

respirations during anesthesia POTENTIAL SOLUTIONS

Dose according to ideal weight Pre-oxygenate Induce rapidly Delay extubation Close monitoring during recovery

PATIENT FACTORS

CESAREAN PATIENTS- normally an emergency POTENTIAL PROBLEMS

DAM: increased workload to heart Respiration compromised Increased risk of hemorrhage- shock/hypotension Increased risk of vomiting/regurgitation- not

normally fasted Hypoxemia Hypercarbia Acid/base imbalance Tissue trauma Cardiac arrhythmias

OFFSPRING: susceptibility to the effects of the anesthetic agents (reduced Cardio and Respiratory function)

Cesarean patients

POTENTIAL SOLUTIONS DAM: IV fluids

Clip patient before induction, in lateral recumbency

Pre-oxygenateReduce anesthetic dosages

OFFSPRING: use doxapram and/or atropine aspirate fluids from mouth

Administer oxygen via face mask, intubate with 18 or 16g IVC

Keep warmEncourage nursing

Patient Factors

TRAUMA PATIENTS POTENTIAL PROBLEMS

Respiratory distress common- decrease in tidal volume, increase in CO2

Cardiac arrhythmias Shock and hemorrhage- hypotension Internal injuries

POTENTIAL SOLUTIONS Stabilize patient if possible Obtain chest rads, ECG Check for other concurrent injuries

Anesthetic Problems and Emergencies: Patient Factors

Change in blood pressure Resulting from a change in cardiac output or

vascular tone Anesthetic depth will affect both parameters Hypotension → decreased tissue perfusion →

tissue hypoxia/anoxia → anaerobic glycolysis → lactic acid production → acid/base imbalance

Monitor blood pressure closely Doppler or oscillometric methods Digital pulse palpation Capillary refill time

TREATMENT OF HYPOTENSION REDUCE ANESTHETIC DEPTH

PRESERVE WARMTH FLUID THERAPY- SHOCK RATE ADMINISTRATION OF EMERGENCY

DRUGS: Corticosteroids Sodium bicarbonate Cardiac inotropes (dopamine,

dobutamine, ephedrine)

Fluid Therapy for Hypotension

Crystalloid fluid administration May have to deliver small boluses for

rapid therapy Crystalloid fluids stay in intravascular

space <2 hours

Watch for fluid overload, especially in cats Monitor heart rate, blood pressure,

mucous membrane color, and capillary refill time

Fluid Therapy for Hypotension (Cont’d)

Colloid fluid administration Helpful if blood pressure can’t be

maintained Remain in the intravascular space longer

than crystalloids Will increase colloidal osmotic pressure

and help stabilize blood pressure Given in smaller volume in conjunction

with crystalloids

Hetastarch, Dextran 40 or 70, 10% Pentastarch, plasma, whole blood

Respiratory problems in the trauma patient Direct trauma to the chest leading to lung

collapse or failure of alveolar gas exchange Must remove air/fluid from chest cavity

prior to anesthesia Deliver supplemental oxygen

Oxygen delivery methods Flow-by-oxygen Nasal catheters Oxygen collars

Thoracocentesis (Chest Tap)

To relieve pneumothorax or pleural effusion from chest cavity

Performed by veterinarian Prepped by veterinary technician Temporary bandage over chest wound Place animal in sternal recumbency or standing

position Shave lateral chest wall between the 7th and 9th

intercostal spaces caudal to point of the elbow Aseptically prepare 4 cm × 4 cm area Prepare a 20- to 22-gauge, 1- to 1½-inch catheter

with a three-way stopcock and large syringe video

PATIENT FACTORS

CARDIOVASCULAR DISEASE POTENTIAL PROBLEMS

Circulation compromised Pulmonary edema common Increased tendency to develop arrhythmias

and tachycardia POTENTIAL SOLUTIONS

Alleviate pulmonary edema (diuretics) Pre-oxygenate Avoid agents that may cause arrhythmias Prevent overhydration- cut fluids in 1/2

Preexisting cardiovascular disease Anemia Shock Cardiomyopathy (primary or secondary) Congestive heart disease (mitral valve

insufficiency) Heartworm disease Coexisting imbalances (e.g., hypoxia,

hypercapnia, electrolyte imbalances)

Bradycardia Most common cardiac anesthetic problem Caused by preanesthetic or anesthetic

drugs Force of cardiac contraction may also be

decreased Blood return to the heart may be

decreased (preload) Treat with drugs or adjustment of

anesthetic depth

Cardiac arrhythmias Caused by anoxia/hypercarbia, poor tissue

perfusion, acid/base imbalance, myocardial damage

Difficult to detect on physical examination; may find dropped beats

Diagnose with ECG and report immediately to veterinarian who will determine the treatment required

Concurrent pulmonary disease is sometimes seen

PATIENT FACTORS RESPIRATORY DISEASE

POTENTIAL PROBLEMS Poor oxygenation of tissues Patient may be anxious and difficult to

restrain Increased risk of respiratory arrest

POTENTIAL SOLUTIONS Avoid unnecessary handling Pre-oxygenate Induce with injectable agents Intubate rapidly; control ventilation Monitory closely during recovery

Respiratory disease Caused by:

Pleural effusion Diaphragmatic hernia

Pneumothorax PneumoniaTracheal collapse Pulmonary edema

Clinical signs Tachypnea Dyspnea Cyanosis

Anesthetic considerations VT is reduced and respiratory rate is decreased in

most anesthetized animals A decrease in VT will result in a decreased

alveolar gas exchange Lighten anesthesia as much as possible in a

patient with respiratory disease Provide intermittent ventilation Evaluate oxygen-carrying capacity with PCV or

pulse oximeter Preoxygenation is necessary prior to induction

Diaphragmatic Hernia Dysnpnea- pre oxygenate Avoid head down positions Intubate rapidly “bagging” patient Pay close attention to pulse ox,

capnograph, and do a arterial blood gas if available.

PATIENT FACTORS HEPATIC DISEASE

POTENTIAL PROBLEMS Liver necessary for drug metabolism, blood clotting factors,

plasma proteins, carbohydrate metabolism Decreased synthesis of clotting factors Possibly hypoproteinemic Dehydration common Anemic and/or icteric Prolonged recovery

POTENTIAL SOLUTIONS Pre-anesthetic blood work Preanesthetic agents must be chosen with care Use inhalant anesthetics

Close monitoring during recovery Preanesthetic agents must be chosen with care

PATIENT FACTORS

RENAL DISEASE POTENTIAL PROBLEMS

Delayed excretion of anesthetic agents Electrolyte imbalances common Dehydration may be present

POTENTIAL SOLUTIONS Pre-anesthetic blood work Rehydrate before surgery Reduce anesthetic dosages IV fluids

Renal disease Kidneys maintain volume and electrolyte

composition of body fluids Renal excretion removes anesthetic agents

and metabolites from the body General anesthesia is associated with

decreased blood flow to the kidneys Diagnosis: urine specific gravity, BUN,

creatinine Offer water up to 1 hour prior to premedication Correct dehydration prior to anesthesia

Anesthetic Problems and Emergencies: Patient Factors (Cont’d)

Urinary blockage Clinical signs

Depression Dehydration Uremia Acidosis Hyperkalemia (can lead to cardiac arrest)

Inhalation agents are less hazardous for the patient

Anesthetic problems will inevitably occur at somepoint in your career. No anesthetic experience isthe same, so beware of the false sense of security!

ANESTHETIC PROBLEMS AND EMERGENCIES

ANESTHETIC PROBLEMS AND EMERGENCIES

The Role of the Veterinary Technician in Emergency Care

ANIMALS THAT WILL NOT STAY ANESTHETIZED

Animals won’t stay anesthetized Check vaporizer setting Check level of anesthetic in the vaporizer Proper ET tube placement or air leakage around it Patient apnea Shallow respirations Proper assembly of anesthetic machine with tight

connections Adequate oxygen flow Anesthetic machine/vaporizer is working properly Agonal breathing vs. light plane breathing

ANIMALS THAT ARE TOO DEEPLY ANESTHETIZED

Animals are too deeply anesthetized <6 bpm; shallow respirations, dyspnea Pale/cyanotic mucous membranes Capillary refill time >2 seconds Bradycardia Weak pulse; systolic blood pressure <80 mm Hg Cardiac arrhythmias; irregular QRS complexes or

VPCs Hypothermia Absent reflexes Flaccid muscle tone Dilated pupils

TREATING EXCESSIVE ANESTHETIC DEPTH

ADJUST THE VAPORIZER: NOTIFY THE VETERINARIAN: BAG THE ANIMAL

1. Close the pop-off valve 2. fill the reservoir bag with oxygen 3. gently squeeze the bag until the

patient’s chest rises slightly (15-20 cm H2O)

4. Repeat until animal shows signs of recovery

PALE MUCOUS MEMBRANES

Pale mucous membranes Preexisting conditions Blood loss during surgery Anesthetic agent that causes

vasodilation and hypotension Hypothermia Pain

TREATMENT OF PALE MUCOUS MEMBRANES

Ascertain the animal’s anesthetic depth: HR, RR, pulse quality, CRT

Consult the veterinarian Fluids, blood transfusion

Anesthetic Problems and Emergencies (Cont’d)

Prolonged capillary refill time (>2 seconds) Blood pressure cannot adequately

perfuse superficial tissues May result from conditions present prior

to induction May be secondary to blood loss during

surgery May be seen in animals in deep

anesthesia

DYSPNEA AND/OR CYANOSIS DYSPNEA: respiratory difficulty CYANOSIS: bluish coloration of the mucous

membranes indicating inadequate tissue oxygenation

Assessment Respiratory character and volume Depth of anesthesia Associated with pain Proper ET tube placement ET tube blockage Oxygen saturation Arterial or end-tidal CO2

Treatment of cyanosis/dyspnea

1. Check O2 flow meter2. Turn off vaporizer and begin to bag the patient (IPPV)If the anesthetic machine is unavailable, an Ambu bag can be used to deliver room air3. Reintubate if necessary

4. Continue until patient improves5. Close monitoring to ensure that cardiac arrest does not occur

Radiographs and thoracocentesis might be needed

TACHYPNEA

TACHYPNEA: rapid respirations CAUSES:

Surgical stimulation Commonly seen with opioid use Associated with light anesthesia

accompanied by tachycardia and spontaneous movement

May be seen in hyperthermic animals

TREATMENT OF TACHYPNEA

CHECK ANESTHETIC DEPTH Is the animal too light?

CAPNOGRAPH READING Obese patients

Assist or control ventilation

RESPIRATORY ARREST Not all cases require immediate action

by the anesthetist: Cessation of respiratory efforts Can lead to cardiac arrest Temporary arrest

May follow injection of respiratory depressants or following a period of prolonged bagging

Evaluate other vital signs HR/pulse quality: MM: ECG Pulse oximeter reading:

Respiratory arrest (Cont’d) True arrest

Requires immediate action Can result from anesthetic overdose,

cessation of oxygen flow, or preexisting respiratory disease

May be preceded by dyspnea or cyanosis and abnormal vital signs

May use Ambu bag, mouth-to-ET tube, or mouth-to-muzzle resuscitation

Use of an Ambu Bag

TREATMENT OF TRUE RESPIRATORY ARREST 1. NOTIFY THE VETERINARIAN 2. Turn off the vaporizer 3. Place ET tube if not already done

Emergency tracheotomy? http://www.youtube.com/watch?v=3doQewrHdhQ

4.Monitor for cardiac arrest 5.Restore oxygen flow and begin bagging

the patient 6. Continue bagging every 5 seconds until

vital signs improve 7. Administer shock fluids 8. Preserve warmth

CARDIAC ARREST Cardiac arrest

No heartbeat is auscultated or palpated Normal QRS complexes are absent No arterial pulse and blood pressure <25 mm Hg Gray or cyanotic mucous membranes Widely dilated pupils, no corneal reflex Agonal breathing

Some prior warning is usually present Respiratory distress or arrest, cyanosis/dyspnea,

prolonged capillary refill time, arrhythmia

CARDIAC ARREST - ABCDEF There is a critical 4 MIN window to

restore oxygen delivery to the brain! Five people (ideal) involved

1 performs chest compressions 2 bags the animal 3 assesses the pulse during compressions and

checks the pulse or ECG when compressions are stopped

4 draws up and administers drugs as per the veterinarian’s instructions

5 maintains a record of the patient’s status and resuscitative treatment

Anesthetic Problems and Emergencies

Cardiac arrest with CPCR A = airway B = breathing C = circulation D = drugs E = ECG

Circulation is the most important step so the correct order is CABDE

CARDIAC ARREST - ABCDEF

AIRWAY and BREATHING;IMMEDIATELY CALL FOR HELP, NOTE THE

TIME! An Endotracheal tube must be

placed! Begin bagging at 1 breath every 10-

12 seconds Do not overinflate


CIRCULATION – cardiac compressions should be initiated

POSITIONING: right side down with feet toward the compressor LARGE DOGS: The heel of the compressor’s

hand should compress the chest against a firm object placed under the dog’s chest just behind the elbow. Also, dog can be placed in dorsal recumbency and compression applied to the caudal 1/3 of the sternum


Medium sized dogs: The chest is compressed between two hands, one underneath the chest and the other at the 5th intercostal space over the heart itself.

Small dogs or cats: compression applied using the thumb to compress the chest against the fingers of the same hand.

Circulation Most important factor is return of spontaneous

circulation (ROSC) Cardiac compressions

Method depends on the size of the animal Compress chest about 1/3 the diameter of the chest wall 1-2 compressions/second generates 100 bpm heart rate Compressions manually force blood through the heart

and into tissues Each compression should produce a palpable femoral

pulse

Circulation (Cont’d) Bag the patient every 10-12 seconds

Simultaneously with compressions Some results should be seen within 2 minutes Internal compressions may be necessary Resuscitation is unlikely to be successful after

15 minutes Once spontaneous cardiac contractions are

established, continue bagging until spontaneous breathing is established (several hours)

These patients are not on their right side- boooo

CARDIAC ARREST - ABCDEF Drugs

Veterinarian authorizes dosage, route, and nature of drugs

Catheterized animals Drugs administered IV followed by rapid fluid

administration Be careful of overhydration

Injections into the base of the tongue or by the intratracheal route are the second choice

Intracardiac injections should be avoided

Commonly used drugs Epinephrine

Cardiac arrest Vasopressin

In place of or alternated with epinephrine Atropine

Anesthesia-related cardiac arrest Dopamine or dobutamine

Increase force and rate of cardiac contractions

Monitor cardiovascular and respiratory function Blood pressure, blood gases, pulse oximetry,

ECG, capnography Drug and fluid therapy varies Assess brain function Repeat arrest within 24 hours is common Following successful ROSC, other conditions

may arise Pulmonary or cerebral edema


ECG Periodically check for spontaneous

contractions by discontinuing external compression and either palpating for a pulse or looking for QRS complexes on the ECG.

Differentiate between different forms of cardiac arrest to more effectively pick the treatment

ECG Don’t use alcohol if a defibrillator is

present Asystole

No electrical activity Ventricular fibrillation

Coarse vertical zig-zag lines resulting from disorganized muscular heart activity

Pulseless electrical activity (electromechanical dissociation, EMD)

Normal or near-normal complexes

Regurgitation during anesthesia A passive process under anesthesia

No retching, just fluid draining from animal’s mouth or nose

Stomach contents may be aspirated into respiratory tract

Most common occurrence in head-down surgical positions and in ruminants

Treatment Immediate placement of cuffed ET tube Clean out regurgitated material with suction

Vomiting during or after anesthesia Common in brachycephalic dogs or nonfasted

animals An active process usually accompanied by retching Usually occurs as the animal is losing or regaining

consciousness Signs

Airway obstruction leading to dyspnea/cyanosis, bronchospasm

Treatment Intubation and suction if unconscious Lower head and clean oral cavity if conscious

Seizures Seen with ketamine administration, after

diagnostic procedures (myelography), or preexisting conditions

Signs Spontaneous twitching; uncontrolled

movements of head, neck, and limbs; opisthotonus; triggered by a stimulus

Treatment Reduce stimuli, postoperative analgesia,

diazepam or propofol, monitor for hyperthermia

Excitement Seen after barbiturate anesthesia or

high opioid doses, as spontaneous paddling and vocalization

Treatment may not be necessary Sedatives may help Naloxone can reverse opioids

Seizures should be differentiated from excitement

Dyspnea in cats Dyspnea is usually caused by laryngospasm

sometimes triggered by removal of the ET tube Laryngeal edema may result from repeated

intubation attempts May breathe with an audible stertor (wheeze)

during inspiration Differentiate from growling during expiration May resolve itself or may need oxygen

administration via facemask, intubation, or a tracheotomy

Is easier to prevent than treat

Dyspnea in dogs Breed-related

Brachycephalic dogs Airway obstruction

Anatomy, foreign objects, postsurgical tissue swelling

Humidified oxygen can be delivered to an awake animal

By facemask, nasal cannula, E-collar, or oxygen cage/tent

anesthetic problems and emergencies

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