ANESTHETIC PROBLEMS

AND EMERGENCIES

CHAPTER 12Every 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!

Can you spot the problem?

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

Propofol? IV IM or Sub Q

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.

WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE?

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 fluidsClip patient before induction, in lateral

recumbencyPre-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

I smell gas

Machine leak- sealed hoses Trache tube leak Inadequate machine scavenging

system Exhausted F-air canister Loose vaporizer cap Vaporizer leak