Anaesthesia - Peri-Operative Accidents And Emergencies

Front 1

Emergency

Back 1

Events that lead rapidly and inevitably to death if untreated or mismanaged

No or little time for preparation

Front 2

Problems

Back 2

Minor, often predictable disturbances that may spontaneously resolve

Individually - little concern

Collectively - may create an emergency

Front 3

How can apnoea occur?

Back 3

De novo - acute event

End result of progressive untended hypoventilation

Sign of cardiac arrest

Front 4

In cardiac arrest when does breathing stop?

Back 4

Breathing continues until medullary ischaemia causes arrest

Front 5

What can cause acute or end-result apnoea?

Back 5

Neural unresponsiveness

Mechanical obstruction, restriction, ineffective ventilation

Front 6

What may cause neural unresponsiveness?

Back 6

Intracranial hypertension, concussion, severe hypothermia, hypocapnia, anaesthetic overdose, normal dose of super-opioids

Front 7

What are the clinical signs seen with an obstruction?

Back 7

Bizarre, "diaphragmatic or paradoxical" breathing pattern

Overinflated respiratory bag if valve closed and FGF high

Gurgling

May be impossible to sigh animal

Front 8

How do you find out if the obstruction is between the bag and the chest wall?

Back 8

Squeeze bag and see if chest wall moves

Front 9

How should you treat respiratory arrest based on neural unresponsiveness?

Back 9

Ventilation should be supported manually

End anaesthesia if cranial nerve reflexes absent -> indicates overdose

Ventilate animal until drug is redistributed

Don't give other drugs, wait until these drugs are out of system

Front 10

What happens if the animal is hyperventilated?

Back 10

May cause hypocapnia, and animal may not breathe

Front 11

Treating a mechanical obstruction?

Back 11

Clear obstruction or bypass with tracheostomy

Vomit aspiration - position head down, mouth gagged if conscious, clear oropharynx of material with towel forceps or haemostats

Lost consciousness - brief cleaning followed by ET intubation and PPV with O2, suction then lavage

Front 12

4 causes of cardiac arrest

Back 12

Myocardial hypoxia (systemic hypoxia, local - hypotension, bradycardia, tachcardia, arrythmias)

Toxaemia

Electrolyte and pH disturbances

Hypothermia

Front 13

How do you treat systemic hypoxia caused by atmospheric hypoxia

Back 13

Increase FIO2

Front 14

Tidal hypoxia

Back 14

Intubate, IPPV O2

Front 15

Alveolar hypoxia

Back 15

Optimise VA and Qt

Front 16

Haemoglobinaemic hypoxia

Back 16

Whole blood or RBCs

Front 17

Stagnant hypoxia

Back 17

Correct cause, fluid, inotropes

Front 18

How does tachycardia cause cardiac arrest?

Back 18

May be due to inadequate anaesthesia

Shorter diastole so no coronary blood supply (occurs during diastole)

Front 19

How do you detect hypotension?

Back 19

Imperceptible peripheral pulses

Diminished blood flow at surgical site

Front 20

prolonged hypotension will lead to post-operative failure in which organs?

Back 20

Kidney and GI tract

Myositis in horses

Front 21

Arterial BP =

Back 21

CO x SVR

Front 22

CO =

Back 22

SV X HR

Front 23

What 3 things affect SV?

Back 23

Preload

Afterload

Contractility

Front 24

How should you treat severe hypotension?

Back 24

Fluids rapidly

Inotropes/alpha-1 agonists like phenylephrine if contractility decreased or decreased SVR

Front 25

How does bradycardia cause cardiac arrest?

Back 25

Insufficient CO to maintain adequate diastolic pressure required for coronary perfusion

Front 26

treatment if cause is vagus?

Back 26

Check surgeon, suspend surgery, otherwise atropine

Front 27

How does tachycardia cause myocardial hypoxia?

Back 27

Excessive work -> O2 requirement > delivery

Front 28

What is VPC?

Back 28

Venricular premature complex - premature contraction

Front 29

What will this be followed by?

Back 29

Ventricular fibrillation

Front 30

What may cause arrhythmias?

Back 30

Myocardial hypoxia

SNS activation (hypoxia, hypercapnia, light anaesthesia, hypotension, hypoglycaemia)

Drugs - alpha 2 agonist, adrenaline

Electrolyte abnormalities (K)

Surgical procedures

Pre-existing heart disease

Conditions e.g. GDV

Front 31

How are arrythmias diagnosed?

Back 31

ECG

Front 32

What is EMD?

Back 32

Electro-mechanical dissociation - no mechanical activity of heart but normal ECG, no palpable pulses

Front 33

How do you treat arrhythmias?

Back 33

May just need adequate anaesthesia and ventilation, sigh animal O2

Front 34

How does toxaemia affect the heart?

Back 34

Reduces myocardial contractility and excitability

Front 35

Give examples of toxaemia occurrences

Back 35

Azotaemia - renal disease

Ketoacidosis - diabetes

Lactacidaemia - hypovolaemic shock

Endotoxaemia - pyometra

Front 36

How should toxaemia be treated?

Back 36

Correct underlying condition

Restore perfusion (restore ECV)

Front 37

Why should excessive levels of anaesthetic be avoided?

Back 37

Lead to prolonged recoveries

Post-operative organ failure - caused by cardiopulmonary depression

Predispose to or cause cardiac arrest

Front 38

Which electrolyte imbalance is most likely to cause cardiac arrest?

Back 38

Hyperkalaemia

Addison's, iatrogenic, renal failure, injury/burns, acidaemia

Front 39

treatment

Back 39

Hyperventilation, fluids, bicarbonate, calcium gluconate, insulin, glucose, peritoneal dialysis

Front 40

No pot no tea

Back 40

Hypokalaemia no T waves

Hyperkalaemia no P waves

Front 41

Why is hypothermia common under anaesthetic?

Back 41

Hypothalamic thermoregulation impaired

Vasodilation of skin bvs

Skeletal muscle activity ceases

Shivering inhibited

Visceral surfaces exposed

Inspired gases cold and dry in non-rebreathing systems

Front 42

Which animals are most at risk?

Back 42

Undeveloped/impaired thermoregulation- old and young

High surface area to volume ratios - neonates, birds, small lab animals

Front 43

Effects of hypothermia

Back 43

Reduced alveolar ventilation

Reduced heart rate and CO

Left-shifted oxyhaemoglobin curve

Increased blood viscosity

Front 44

Consequences

Back 44

Prolonged recovery

cardiac arrest -Ventricular fibrillation

Front 45

How to prevent hypothermia

Back 45

Increase operating room temp.

Do not lay animals on cold, un-insulated surfaces

No draught exposure

BAIR hugger, aluminium foil, bubble wrap, blankets, heat lamps, heat incoming fluids

Front 46

Why might the animal get skin burns?

Back 46

Hypothermia -> vasoconstriction, so no heat removed by venous supply

Front 47

How to prevent with anaesthetic factors

Back 47

Short-acting anaesthetics

Do not over-ventilate

Not too deep anaesthesia

Rebreathing system where appropriate

Front 48

How to prevent with surgical factors

Back 48

Avoid unnecessary wetting and clipping of non-surgical areas

Minimise surgical time

Exposed viscera moistened with warm irrigation fluids

Small incision size