Equine anesthesia

Question 1

5 stages of anesthesia

Answer 1

Pre-anesthetic, sedation, induction, maintenance, recovery

Question 2

What measures do you take during your pre-anesthetic physical exam and why?

Answer 2

• pay special attention to respiratory and cardiovascular systems
• identify murmurs, arrhythmias – use in context of pt age too
• subclinical resp. disease can become overt under anesthesia

Question 3

How to know horse is adequately sedated

Answer 3

1. 5-point stance
2. head drop
3. minimally responsive to external stimuli
4. lip dropped

Question 4

Common induction combos in equines

Answer 4

Ketamine and diazepam (dissociative + benzodiazepine – tend to maintain reflexes well – 10-15mins)

Ketamine and propofol (can use less prop with ketamine)

Telazol (much smaller dose than ketamine and diazepam)

Ketamine and guaifenesin (guaifenesin = muscle relaxant–given on IV bolus till desired effect = buckled knees)

Question 5

Describe equin intubation process and what to do if resistance occurs

Answer 5

Blind intubation -> insert mouth gag -> pass tube into pharynx and layrnx
- if resistance occurs, retract 10cm and rotate 90º and re-advance

Question 6

Why is correct positioning of sedated/anesthetized horse crucial?

Answer 6

Preventing neuropathies and myopathies

Question 7

What type of scavenging system does equine inhalant anesthesia require and why?

Answer 7

Active scavenging – O2 flow rates too high for cannister-type scavenging (small animal)

Active scavenging system: consists of a piped vacuum and duct system that carries the waste anesthetic gas (WAG) away from the anesthesia machine.

Passive scavenging system: relies on the upstream flow of gas coming out of the machine to passively flow out of the system, similar to how water flows through and out of a garden hose (a garden hose doesn’t need suction at the end of it to pull the water out of it).

Question 8

TIVA vs PIVA – benefit of PIVA

Answer 8

Total Intra-Venous Anesthesia

Partial Intra-Venous Anesthesia

PIVA allows for the benefits of both inhalant and TIVA anesthesia

Inhalant vs TIVA

Question 9

How is anesthetic depth monitored in horses?

Answer 9

• light plane of anesthesia desired
• slow (NOT absent!!) palpebral, strong corneal, tearing, slow nystagmus
• dissociatives interfere with above eye signs
• muscle relaxtion
• Arterial BP (higher = waking up more)
• EKG

jug vein, pt of shoulder and base of heart

Question 10

Importance of monitoring Arterial BP and ideal value

Answer 10

• MAP > 60mmHg
• BP indicates plane of anesthesia and good muscle perfusion (avoid myopathies!)

Question 11

How to increase a hypotensive BP

Answer 11

decrease inhalant, increase fluids, administer dobutamine (inotrope+)