Anaesthesia for the Critical Patient: Is it Different?

Question 1

Why is anaesthesia different in critical patients?

Answer 1

Emergency patients have minimal ‘physiological reserves’ to tolerate the stress of anaesthesia

Question 2

Why Are Emergency Patients a Challenge?

Answer 2

• Unstable cardiorespiratory system
• Altered circulating fluid volume
• Metabolic derangements
• Time pressures and patient status with emergencies
• Potentially unknown/limited history
• Emotional and financial pressures from the owners

Question 3

Anaesthetic challenges with GDV cases?

Answer 3

• Electrolyte imbalances (potassium and calcium) with cardiac arrhythmias
  
  • Hypokalaemia
• Hypovolaemia
• Respiratory compromise
• Possible regurgitation and aspiration
• Pain and distress
• Metabolic acidosis and increased lactate

Question 4

What sort of potassium changes are we likely to see with GDV cases and why?

Answer 4

• Hypokalaemia
  
  • Any chronic or acute GI disease is likely to leach potassium into swollen gut wall and into gut lumen
  • Hypokalaemia causes tachycardia, loss of T waves and can easily go into ventricular fibrillation

Question 5

What premedication for critical patients?

Answer 5

• Drugs such as the alpha-2 agonists which have major cardiovascular effects should generally be avoided
• Generally would use an opioid

Question 6

What analgesia for critical patients?

Answer 6

• Pethidine administered intramuscularly is often a good choice
  
  • Short acting, excellent analgesia with some sedation, minimal effects on the cardiovascular system
• Methadone or morphine suitable but may cause a degree of bradycardia (not often seen as so painful) and emesis

Question 7

What should you do prior to inducting a critical patient?

Answer 7

• Pre-stabilise - oxygen and fluids
• ECG to examine the electrical rhythm of the heart with treatment as necessary
• Oxygen for a minimum of five minutes
• Have emergency drugs (doses calculated) to hand plus syringes/needles

Question 8

What induction agent for critical patients?

Answer 8

• Any induction agent can be used but give slowly to effect until you can get control of the trachea
• No one drug is safer than the others
• Emphasis on minimal effective doses to allow endotracheal intubation

Question 9

What should you do post induction?

Answer 9

• Attach to a suitable breathing system
• Administer oxygen (+/- inhaled anaesthetic agent) and ventilate lungs as necessary
• Know what MAC is so you know where to put the dial
• Check pulses
• Apply monitors
• Continually assess physiological status of the patient

Question 10

What could you do to reduce the delivered inhalation agent during anaesthesia (to reduce CV depression)?

Answer 10

• Use intravenous infusions such as fentanyl, lidocaine or ketamine to provide intra-operative analgesia and MAC reduction (PIVA)
  
  • The sicker the dog the more likely to add these things in

Question 11

What should be monitored during recovery?

Answer 11

• Closely monitor cardiorespiratory status
• Check temperature regularly
• Assess glucose
• Analgesia should be given as necessary to ensure patient comfort