ANESTHETIC PROBLEMS AND EMERGENCIES

1. ANESTHETIC PROBLEMS AND EMERGENCIES CHAPTER 12 Every anesthetic procedure has the potential to cause death of the animal

2. Emergencies are uncommon and the overwhelming majority of patients recover from anesthesia with no ill lasting effects

3. WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 1. HUMAN ERROR!

4. 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?

5. HUMAN ERROR • LACK OF FAMILIARITY WITH THE ANESTHETIC MACHINE OR DRUGS USED The confident, knowledgeable, experienced RVT! The not so confident kennel worker who was asked to assist in surgery today.

6. 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

7. 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

8. 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.

9. 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!

10. 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

11. EQUIPMENT FAILURE • ANESTHETIC MACHINE MISASSEMBLED Take 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

12. 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 compressed If 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.

13. 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

14. 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.

15. 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.

16. WHY,WHY,WHYDO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 4. PATIENT FACTORS pre-operative status age concurrent disease breed

17. 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

18. 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

19. 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

20. 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

21. PATIENT FACTORS • SIGHTHOUNDS • POTENTIAL PROBLEMS • Increased sensitivity to barbiturates • Lack of body fat for redistribution/elimination of the drug • POTENTIAL SOLUTIONS • Use alternative agents

22. 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

23. 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)

24. Cesarean patients • POTENTIAL SOLUTIONS • DAM: IV fluids • Clip patient before induction, in lateral recumbency • Pre-oxygenate • Reduce anesthetic dosages • OFFSPRING: use doxapram and/or atropine aspirate fluids from mouth • Administer oxygen via face mask, intubate with 18 or 16g IVC • Keep warm • Encourage nursing

25. 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

26. 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

27. TREATMENT OF HYPOTENSION • REDUCE ANESTHETIC DEPTH • PRESERVE WARMTH • FLUID THERAPY- SHOCK RATE • ADMINISTRATION OF EMERGENCY DRUGS: • Corticosteroids • Sodium bicarbonate • Cardiac inotropes (dopamine, dobutamine, ephedrine)

28. 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

29. 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

30. 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

32. 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

33. 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

34. 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)

35. 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

36. 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

37. 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

38. Respiratory disease • Caused by: Pleural effusion Diaphragmatic hernia Pneumothorax Pneumonia Tracheal collapse Pulmonary edema • Clinical signs • Tachypnea • Dyspnea • Cyanosis

39. 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

40. 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.

42. 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

43. 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

44. 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

45. 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

46. ANESTHETIC PROBLEMS AND EMERGENCIES Anesthetic problems will inevitably occur at some point in your career. No anesthetic experience is the same, so beware of the false sense of security!

47. ANESTHETIC PROBLEMS AND EMERGENCIES The Role of the Veterinary Technician in Emergency Care

48. 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

49. 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

50. 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