Equine Anesthesia Flashcards
How is peripheral perfusion evaluated in equine patients?
- jugular fill
- temperature of ears and distal limbs
- digital and facial artery pulse quality
- mucous membrane color, texture, and CRT
What are 5 pertinent parameters for the pre-anesthetic evaluation of equine patients?
- mentation and temperament - difficult handling, anxious, depressed, calm
- gait assessment - ataxia, lameness, pain
- accurate body weight
- medical history - concurrent medications, prior anesthetic record
- disease/condition-specific considerations - colic, blood loss, pregnancy, foal
What basic components of the CBC are necessary for equine anesthesia? What are some concerning findings?
PCV/TS
- leukocytosis, neutrophilia = pneumonia, other infection
- leukopenia = sepsis
What 4 aspects of a chemistry are the most important for equine anesthesia? When is a full panel performed?
- creatinine
- fibrinogen
- lactate for blood volume status
- electrolytes - Na, K, Cl, Ca, Mg
systemic disease
What is necessary prior to walking to the induction stall?
adequate anxiolysis
What food withdrawal period is recommended for horses? Why is it controversial?
4-12 hrs
- increased acidity with prolonged fasting and slowed GI transit
- decreased gastric size causes less pressure against the diaphragm = reduced atelectasis
What is the water withdrawal period like for horses?
none —> free access to water recommended
How are horses prepared before premedications are given?
- pull shoes
- clean feet
- rinse mouth
What are the 4 components of an equine premedication protocol?
- phenothiazine - Acepromazine
- alpha-2 agonist - Xylazine, Detomidine, Medetomidine, Dexmedetomidine, Romifidine
- opioid - Butorphanol, Morphine, Methadone
- benzodiazepine - Midazolam, Diazepam
Why is there commonly a separate sedation stall offered for equine patients?
offers a quiet environment with reduced stimuli, which allows for increased effect of premedications and reduced doses required for pre-anesthetic sedation
- give Acepromazine 15 mins prior to walking to the induction area
What pre-medication sedatives are recommended within the induction stall?
Xylazine +/- Butorphanol
What is done if a horse is not sedated enough for induction?
- allow time for onset - give 5-7 mins!
- additional Xylazine bolus up to 1 mg/kg
- detomidine bolus
- ensure the stall is quiet and minimize auditory/tactile stimuli
What are the 3 major combinations for equine induction? Why/when are they used?
- Ketamine + Xylazine - muscle relaxation, less ataxia; good for short procedures
- Ketamine + MIdazolam - reliable muscle relaxation, reduced MAC
- Ketamine + Guaifenesin - allows for reduced alpha-2 agonist usage for colic cases and cesarean sections
How is Ketamine + Guaifenesin induction given? What are the 3 steps?
with Guaifenesin in a pressure bag
- start with a slow drip for central sedation
- increased drip rate to a stream for central muscle relaxation - should see tremoring pectoral muscles and carpal knuckling
- inject Ketamine
What are the 4 most common restraint choices during equine induction?
- head/tail rope
- head rope only
- swing-gate
- sling
How are equine ET tubes checked? What other equipment is used?
cuff leak check while inflated for 5 mins
- sterile lubricant
- air syringe
- mouth gag PVC tube
How can horses be nasally intubated?
- lubricate a cuffed nasotracheal tube with Phenylephrine gel
- insert the stylet
- use the stylet to guide the tube into the trache
What are the 8 steps of equine induction?
- rinse mouth
- add sedation as needed
- place head and tail rope, swing-gate, or sling
- induce anesthesia
- palpate pulse
- intubate
- lubricate eyes
- hoist to table
What 3 inhalant anesthetics are used on horses? What 2 complications are common?
- isoflurane
- sevoflurane
- desflurane
- hypoventilation - may need ventilator
- hypotension - potent vasodilators
What 5 MAC-sparing medications are recommended
- benzodiazepines
- alpha-2 agonists
- opioids
- lidocaine
- ketamine
What locoregional blocks are commonly used on equine patients?
- epidural
- distal limb blocks
- maxillary/mandibular blocks
What combination is recommended for TIVA in equine patients? What bolus can be added? When is this most commonly done?
triple drip - Guaifenesine, Ketamine, Xylazine +/- Midazolam
2:1 Ketamine/Xylazine —> monitor anesthetic depth closely!
shorter procedures 45 mins to 1 hr, like castrations and imagining studies —> still require intubation and supplemental O2
What are the 3 major analgesic opioids used in equine patients?
- Butorphanol - kappa agonist/mu antagonist for mild-moderate pain
- Morphine - mu agonist for moderate-severe pain
- Methadone
Why must morphine be given to equine patients carefully?
may increase MAC - associated with excitement
