Equine Dr. Bennett Flashcards
Standing vs general anesthesia
many procedures can be perfomed in standing horse
using local nerve blocks & alpha2 CRI
cheaper, faster & less risk to horse
Pre operative assesment
Normal rate?
What is the most common arrhythmia in fit horses?
murmurs?
20-45 bpm
2° AV block - dissapears w/ exercise
very common
respiratory system
COPD common in horses > 10 y housed inside
What do you need to remember about premedication in horses?
Never anesthetise and unsedated horse!
Acepromazine
used in combo w/ other sedatives
oral or injectable
indications for Acepromazine
provides some level of tranquilization
cardioprotective
assoicated w/ reduced risk of anesthetic mortality
contraindications for Acepromazine
hypovolemic animals
young foals
breeding stallions due to risk of priapism
What type of drugs are the mainstays for premedication of adult equines
Alpha2 adrenoceptor agonists
xylazine
detomidine
romifidine
medetomidine & dexmedetomidine
potent sedative & also analgesics
Which Alpha2 to use, depends on time you need!
Romifidine (>80 min)> Detomidine (≈ 80 min)>Metedetomidine (>60 min)> Xylazine (20 min)
Alpha2/Alpha1 selectivity:
Xylazine<detomidine></detomidine>
Detomidine & medetomidine produce greater ataxia
Romificine gives lease analgesia
Other drugs used for premed in equines
Opioids
- butorphanol
- morphine
- methadone
- buprenophine
Benzodiazepines
- diazepam
- midazolam
What are the side effects of opioids in horses
Decr GI motility
What age are benzos predominantly used for
foals < 2 mos of age
for tranquilization
few CV & respiratory effects
What are the aims of induction in equine
Which drug helps acheive these aims nicely!
Quiet environment
controlled, slow & gentle
Ketamine!
How are equines intubated
usually blindly & oral
but can be nasal
disengage epiglottis from soft palate
What is inhalant drug for equines
Isoflurane (only licensed drug)
MAC 1.3% - sx usually requires 20-40% above MAC
Equipment used in anes for equines
LA circle system
Vaporizer 4-6% initial
2-3% maintenance
O2 6-10 L/min initial
5-10 mL/kg/min maintenace
What does TIVA for horses consist of
GG
Alpha2 agonist (xylazine/detomidine/romifidine)
Ketamine
“Triple drip”
What type of ECG setup is used in horses
Lead 1 / Base-Apex
Black = behind left elbow (on PMI)
White = over R jugular furrow
Red = left stifle
What arteries are used for art BP?
Dorsal metatarsal
Transverse facial
What is goal for MAP in equines
> 70mmHg
important for info on perfusion vs indication of depth of anes.
What does pulse oximetry measure?
What is minimum acceptable value?
Hgb saturation
90%
How do you monitor depth of anesthesia in equines
Subjectively!
Eye position
- 1 eye central, 1 eye rotated back or forward
- slow palpebral reflex
- lacrimation
anal tone
What are signs that equine is too light?
ANY limb movement
ANY swallowing
ANY nystagmus
A moving horse is an awake horse!
What are types of pain management drugs in horses
NSAIDs
Alpha2 agonists
Opioids
Regional anesthesia
Epidural anesthesia & analgesia
Intra-articular anesthesia & analgesia
NSAIDs for horses
flunixin
phenylbutazone
Alpha2 agonists for horses
CRI
medetomide/dexmedetomidine
or
detomidine
or
romifidine
Opioids for horses
butorphanol
morphine
methadone
Common problems during equine anesthesia
Hypotension
Hypoventilation
Hypoxemia
Recovery
Why does hypotension cause problems
reduced organ perfusion
reduced delivery of oxgen to tissues
incr risk of myopathy
Problems seen with hypoventilation
leads to respiratory acidosis
incr risk of hypoxemia
incr risk of arrhythmias
Problem with hypoxemia
contributes to diminished oxygen delivery to tissues
incr risk of myopathy
Problems encountered during recovery
Myopathy
Neuropathy
Spinal cord malacia
Recovery quality
How to handle common hypotension seen during anes.
- Try to reduce vaporizer setting
- incr. fluids
- use vasoactive drug: dobutamine
What defines adequacy of ventilation?
How measured?
Tx?
Amount of expired CO2
Aterial BG/capnograph
if possible decr anesthetic, use IPPV
What is common cause for hypoxemia in eq anes
Prevention? Tx?
V:Q mismatch
incr FiO2
mechanical ventilation
Beta2 agonist : salbutamol
Change position
reduce pressure from abdominal contents
Prevention of myopathy in equine
monitor arterial BP & maintain!
Minimum MAP of 70mmHg
Problems seen in recovery
excitement/disorientation
post anesthetic myopathy
respiratory obstruction
neurogenic paralysis
hemorrhagic myelopathy
Important difference between horses & donkeys
Temperament
- more stoical & tolerant
Pharmacokinetics
- metabolise some drugs more rapidly than horses
- less sensitive to alpha2 agonists
- metabolise ketamine more rapidly
- more sensitive to guaifenesin - incr risk of resp arrest
TIVA:
5% GG + 0.5 ml/mL xylazine + 2mg/mL ketamine
2mL/kg/h approx
