Small Animal Complications in Anaesthesia

Question 1

What is the most important parameter in anaesthesia?

Answer 1

Oxygen delivery/tissue perfusion

Question 2

What parameters effect tissue perfusion?

Answer 2

Cardiac Output
Heart Rate
Ventilation/oxygenation
Blood Pressure
Circulating Volume

Question 3

What is bradycardia?

Answer 3

Abnormally low Heart rate

Question 4

What factors cause Bradycardia?

Answer 4

Anaesthetic drugs
Toxaemia (potassium levels)
Excessive vagal tone
Hypoxia (terminal event)

Question 5

How can vagal tone be stimulated?

Answer 5

Tracheal, laryngeal, pharyngeal stimulation
Pressure on eyeball
Visceral distension or inflammation

Vagal stimulation reduced heart rate

Question 6

What Anaesthetic drugs can cause Bradycardia?

Answer 6

Opioids:
Methadone
Buprenorphine
Volatile Agents:
Isoflurane
Alpha-2 agonists:
Medetomedine
Xylazine
Dexmedetomidine
Induction agents:
Propofol

Question 7

Before reacting to bradycardia what need assessing?

Answer 7

Tissue perfusion
Check SpO2 and Blood pressure
(HR could be low but CO high so perfusion is normal)

Question 8

How can you treat bradycardia?

Answer 8

Treat possible cause first
If not possible give atipemazole (reverses alpha-2 agonist)
Consider anticholinergics to increase HR (atropine)

Question 8

How can you treat bradycardia?

Answer 8

Treat possible cause first
If not possible give atipemazole (reverses alpha-2 agonist)
Consider anticholinergics to increase HR (atropine)

Question 9

What is Tachycardia?

Answer 9

Abnormally high heart rate

Question 10

What can cause Tachycardia?

Answer 10

Too light anaesthetic - response to nociception
High CO2 (CO2 is a sympathetic stimulant so increases HR)
CNS disturbances
Low blood pressure/cardiac disease (compensating)
Anticholinergic drugs

Question 11

How can you treat Tachycardia?

Answer 11

Treat possible cause first
Use opioids, ketamine or lidocaine if too light
(Increasing volatile agents doesn’t affect nociception so this isn’t very useful)

Question 12

What causes ventricular/atrial ectopic beats?

Answer 12

○ Circulating catecholamine
Adrenaline - stress/pain
○ Lack of oxygen
○ Too much CO2
○ Dangerously low BP
○ Anaesthetic drugs
○ Heart disease

Question 13

How can you treat ventricular/atrial ectopic beats?

Answer 13

Check if output is compromised
○ BP
○ SPO2%
If VPCs are multiform (different parts of heart) or in sequences (paroxysms)
More serious
Check depth of anaesthesia
○ Consider IV opioid
Check not too much CO2 in body
Inject lidocaine

Question 14

What is hypotension?

Answer 14

Abnormally low blood pressure

Question 15

What can cause incorrect hypotension reading?

Answer 15

Incorrect equipment (wrong size cuff/position)

Question 16

How can you check for hypotension?

Answer 16

Doppler
Feel pulse pressure
Urine production

Question 17

What causes hypotension?

Answer 17

Isoflurane being too high
Hypovolaemia and haemorrage
Cardiac insufficiency

Question 18

How can you treat hypotension?

Answer 18

Determine cause
○ Reduce volatile agent if too high
○ Give fluids
○ THEN consider treatment:
§ Dobutamine in horses (inotrope - heart pumps harder)
Vasopressor (norepinephrine)