Anaesthesia Flashcards
Preparation for anaesthesia
Starvation - controversial but feed night before and then not in the morning
Remove shoes/bandage feet
Clean mouth
IV canular
Equine pre-med
ACP IM (or IV) - cardioprotective, 45 mins before IV sedation
Alpha-2 agonist - gives good sedation prior to induction
Opiate - butorphanol if non-painful, morphine if painful
Equine induction agents
Ketamine IV (horse will fall down, very rigid) with Midazolam IV (muscle relaxant)
Propofol IV (can use in foals but not common)
Methods of anaesthesia in a horse
Free fall (if too dangerous to assist)
Assisted (one person, field or very small horse, hold head up so fall back)
Assisted (multiple people, knock down box)
Assisted (crush door, knock down box)
‘Flop’ techniqe with foals
Field maintenance of anaesthesia
Ketamine +/- alpha-2 top ups
- up to 1/3 induction dose every 10 mins
Triple dip - guaifenesin (muscle relaxant) + ketamine + alpha 2 agonist
- can’t give for more than 90 mins due to accumulation of guaifenesin -> very ataxic recoveries
Hospital meintenance of anaesthesia
Intubation
Circle breathing system with inhalant oxygen +/- air
Isoflurane
FIeld monitoring of anaesthesia
Manual HR and RR
Increased muscle tone - light
Increased resp rate with pain - light
Delayed action of ketamine so make sure to do top ups at least every 10 mins
Hosptial monitoring of anaesthesia
Same as SA
Blood gases useful, especially in colic
With foals monitor blood glucose and temperature
Nystagmus with inhalational = very light
Main physiological changes under anaesthesia
Hypoventilation (on inhalational not ketamine)
Decreased cardiac output
Hypotension (reduced CO and vasodilation)
Atelectasis and resulting V/Q missmatch (dependent lung lobe can collapse)
Hypoxaemia (supply oxygen, ventilate if hypoventilation is contributing)
Field recovery from anaesthesia
Kneel on neck until fighting to get up, holding nose towards you
Then stand well back with long rope on head collar
Hospital recovery from anaesthesia
Kneel on neck until they swallow - pull ET tube out
Intranasal oxygen
Pull lower leg forward
Empty bladder (catheter)
Two main methods of hospital recovery from anaesthesia
Free recovery - shut door and let horse stand by itself
Ropes - attached to head collar and tail, pull when horse stands up, can be risky
How long should a horse take to get up after anaesthesia
Approx 20 mins + 20mins per hour of anaesthesia
Complications of equine anaesthesia
Myopathy
Fractures
Neuropathies
Spinal cord malacia
Respiratory issues during anaesthesia
Respiratory obstruction during recovery
Post operative impactions
Myopathy in equine anaesthesia
Due to muscle compression and under perfusion
Keep blood pressure above mean of 70mmHg to reduce risk
Soft theatre bed
Commonly affects gluteal muscles in dorsal recumbency, and triceps in lateral
Mild to severe lameness on recovery
Swollen hot muscles
Manage with sedation, pain relief, steroids, IV fluids, support