Equine Anesthesia Flashcards
What side effect should you be cautions of if using acepromazine in horses?
Penile prolapse
____________ can cause abortion in the third trimester of pregnancy
Xylazine
What are common prodecures requiring anesthesia in equines?
Colic
Arthroscopy
Castration
Upper airway dz (tie-back, ethmoid hematoma, guttural pouch mycosis)
What are the basics you should asses in your clinical exam before an anesthetic procedure?
History
Heart rate
Respiratory rate
Mucous membrane (colour and CRT)
Hydration status
What are the basic lab test that should be run prior to anesthesia?
Basic hematology and biochem
PCV
TSP
Urine SG
What site is usually used for venous catherizaiton in horses?
Jaguar
—aseptic prep and local anesthetic infiltration
What catheter size should be used in an adult horse
12g
How should you prepare a horse for anesthesia?
Starve for 4-6 hours
Withhold water for 2 hours
Pull out all shoes
Rinse out mouth
T/F: a2 agonsits can cause potent sedation with some analgesic effects?
True
Which of the following is the most potent a2 agonist?
Xylazine
Detomidine
Romifidine
Detomidine
What opioid is most commonly used as an analgesic in horse and when would it be contraindicated?
Butorphanol
Contraindicated in severe pain
What premedication can reduce GI mobility and predispose a horse to colic?
Opioids and a2 agonsits
They are still be best options for sedation/analgesia in horse
What premedicaitons can provide analgesia in horse?
A2-agonists Fluxinine megulmine Meloxicam Butorphanol Methadone/morphine
When should you administer the muscle relaxant?
Before induction agent
What are muscle relaxants used in horses?
GGE = glyceryl guaicolate ether
Benzodiazepine: diazepam or midazolam
What agents are used for induction in horse?
Ketamine
Thiopentone
What diameter tube is used in intubation of horse?
26mm or an average 50kg horse
How should a horse be positions on the theatre table
Cushion on pressure points (head, shoulder, pelvis, and limbs)
Stretch limbs apart -> encourage venous return
Protect eyes from trauma
Only in one lateral recumbency!
What type of circuit do you use for equine anesthesia ?
Circle, rebreathing
What is the o2 flow rate for induction and maintenance in horse ?
20ml/kg/min induction
10ml/kg/min maintenance
T/F: for maintenance in horse, iso/sevoflurane is supplemented in intravenous drugs
True
What is the most common protocol for PIVA and TIVA?
A2 agonsit (xylazine, detomidine, romifidine, medetomidine)
Muscle relaxant (GGE or Midazolam)
Hypnotic agent (ketamine)
Provides.. narcosis, analgesia, and muscle relaxation
What are the goals of combining PIVA and inhalation anesthetic?
MAC reduction
Provide analgesia
Reduce adverse CVS effects
What drugs are in PIVA for horse?
Ketamine
Medetomidine
Lidocaine
What are advantages of TIVA over inhaltion all anesthetics?
Less CV depression Superior analgesia Less likely to move in response to surgical stimulus Decrease surgical stress Lower morbidity and morality Better quality of recovery
What are to two types of TIVA in horses ?
Triple drip -ketamine, Guaifenesin, xylazine/romifidine
Double drip
Alternatively to a triple drip, you can top up you anesthesia with intermittent boluses. What can you use?
Ketamine
Diazepam/midazolam
What lead configuration for ECG is used in horse
Lead 1 (base-apex)
What reflexes can you use for monitoring anesthetic depth?
Palpebral reflex weak No nystagmus Weak anal tone Stable autonomic reflexes Non-responsive to surgical stimulus
Too light: lacrimation, nystagmus, corneal reflex, tachypnea/tachycardia, movement
What are signs that you anesthesia is too deep?
Absent palpebral reflex
Absent corneal reflex
Dry cornea
Bradypnea, apnea, bradycardia, and hypotension
What are complications can occur in horse anesthesia ?
Sudden heart failure Hypotension Hypoventilation Hypoxemia Myopathy Myelopathy Excitement and ataxia Nasal obstruction Jugular vein thrombosis
How can you treat anesthesia related hypotension ?
Address specific underlying problem
Reduce anesthesia admin
Volume resuscitation -crystalloid or colloids
Cardioacive drugs (dobutamine, phenylephrine)
How can you manage hypoventilation during anesthesia ?
Mechanical ventilation
Set resp rate and volume
Target - 35-34mmHg pCO2
What myopathies are associated with anesthesia?
With rhabdomyolysis
- compartmental myopathy
- malignant hyperthermia
Without rhabdomyolysis
-hyperkalemic periodic paresis
What pathoglical changes occur in myopathy?
Myoglobinuria and hyperglobulinemia
Muscle enzymes (elevated CK, AST, and LDH)
Electrolyte
- elevated P and K
- decreased Na, Cl, and Ca
BUN and CREA elevated
Inflammatory leukogram
What are predisposing factors to compartmental myopathy ?
Heavily muscled horse
Fit or nervous horse
Persistently low MAP <70mmHg
Improper positioning
Prolonged anesthesia time >2hours
Halothane
What are signs of a compartmental myopathy?
6Ps (pain, paresis, paralysis, pallor, pulselessness, poikilothermia)
Failure to stand on specific muscle group
Muscle feels hard and is severely painful
Myoglobinuria-> renal failure
How do you treat compartmental myopathy?
Fluids
Analgesic, muscle relaxant/ sedative
Oxygen radical scavengers: DMSO
Physiotherapy
Fasciotomy-decompression
What are predisposing factors to malignant hyperthermia?
Mutations in ryanodine gene —> dysfunctional release of Ca
Halothane
Stress
Depolarizing muscle relaxants (succinylcholine)
Improper positioning
Signs and symptoms of malignant hyperthermia
Profuse sweating Tachypnea Tachycardia and arrhythmia Hypertension Prolapse of third eyelid Flared nostrils Contracted masseters Muscle rigidity and twitching Myoglobinuria Death
How can you prevent malignant hyperthermia?
Correct positioning and padding
Pre-anesthetic dantrolene
Maintain normal BP
What is the treatment of malignant hyperthermia?
Dantrolene Water/alcohol bath ACP for vasodilation Na bicarb for acidosis TLC
What is hyperkelemic period paralysis (HYPP)?
Generic in Quarter horses
Mutation resulting in failure of Na channels to deactivate - excessive Na influx and K outward flux
What are signs of HYPP myopathy?
Respiratory distress and laryngeal paralysis Swaying Staggering Dog-sitting Recumbency Prolapse of eyelid
How do you treat HYPP myopathy?
Acetazolamide
Dextrose
Ca gluconate
TLC
What are possible causes of neuropathy ?
Ischemia, pressure, and stretching
How can you prevent neuropathy?
Correct position and padding
Remove head halter during anesthesia
Maintain BP
How can we see nasal edema as a complication in equine anesthesia?
Gravitational (hypostatic) fluid extravasation
—> keep nasal tube in place until horse stands and provide O2
How can we reduce excitement during recovery?
Minimize stimulation
Sedate with romifidine/detomidine
How should you premeditate a foal?
In presence of mother
Can used benzodiazepines in foals, doesn’t cause excitement like in adults
What is used for induction of a foal?
Propofol, ketamine
A one week old 45kg foal presents for anesthesia to surgically repair a patent urachus and an accompanying ruptured bladder.
For low long would you starve this foal before the anesthetic procedure ?
No fasting
Foals are not prone to regurgitation and are prone to hypoglycemia
A one week old 45kg foal presents for anesthesia to surgically repair a patent urachus and an accompanying ruptured bladder.
What are 5 physiological complications that this foal is more predisposed to during anesthesia compared to normal adult horses?
Prone to hypoglycemia (high metabolic rate and low storage)
Low BP / High HR
Prone to hypothermia
Lower liver function -require less drugs
Respiratory system not fully developed- poor ventilation -> hypoxemia
T/F: donkeys are more resistant to sedatives and anesthetics
True
-increase dose by 30%
T/F: the half life of GGE is shorter in donkeys but they are more sensitive to ketamine
False
Ketamine half life is shorter —> expect more frequent top ups
More sensitive to GGE
