anesthetic problems and emergencies chapter 12 every anesthetic procedure has the potential to cause...
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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
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
WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
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 or leak Hose becomes disconnected Obstruction or leak occurs Knob can become stripped, check bobbin tract*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.
WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?
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.
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
Respiratory Volumes
Tidal volume-
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual volume
Minute Volume
Respiratory Capacities(involve 2 or more pulmonary volumes)
Inspiratory Capacity
Functional Residual Capacity
Vital Capacity
Total Lung Capacity
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
How to fix it… Low heart rate- access depth- BP, jaw
tone, opiods. Fix- decrease anesthetic , consider
anticholincergic
Increased heart rate- same checks as above
Fix – turn up gas
But…. Low BP- HR increases as compensatory stage – decrease gas
Lost ECG or sudden abnormal reading
Check patients vitals manually Check lead attachment, apply more
alcohol IF you cannot hear heart rate, tell DR.!
Low EtCO2
Check pulse and BP- precursor to cardiac arrest
If normal BP and pulse: check O2 flow rate
If BP is low- decrease anesthetic
High EtCO2- check trache tube, soda lime
Then use ventilator, esp. in obese patients
Low Blood Pressure
Low- check cuff size, and position- is it on a joint?
Check with a doppler if oscillometic is being used
Check anesthetic depth, decrease vaporizer
- Still low?- Try shock rate- Still low?- Alert vet and start colloids or what ever
Dr. prescribes.
High Blood Pressure
Check cuff size and position Check against doppler Check anesthetic depth, and increase
gas Consider drugs given, type of surgery,
or what surgeon is doing to patient at that time
Cut fluids off