Equine Anesthesia Flashcards
general info
Most commonly anesthetized of all large animals
temperment and size pose a challenge
Stallions: penile prolapse/priapism from ace
Xylazine abortion in 3rd trimester
Common procedures
Colic
arthroscopy
castration
upper airway
Prep
Clinical exam
Lab tests
Clinical examination
hx
basics:
HR, RR, mm (color & CRT)
hydration status
Lab tests
Basic hematology and biochem:
PCV, TP, urine SG
compromised patients require more specific laboratory tests
Venous catheterization
usually jugular vein Aseptic prepping of site Local anesthetic infiltration Catheter placement, 12 gauge (adult horse) Suture catheter to skin with nylon
Preanesthetic preparation
Starve for 4-6 hours
Withhold water for at least 2 hours
Pull out all horse shoes
Rinse mouth with pressurized water to clear foreign matter that might attach to endotracheal tube and possibly contaminate/infect lungs
Premedication
Analgesia Butorphanol Methadone/morphine A2 adrenergic drug (xylazine, romifidine, detomidine) Flunixine meglumine 1.1 mg/kg Meloxicam
Considerations during premedication
preferably in an induction (-cum-recovery) box
Padded stall, swing door, tiltable table
Restrain horse properly during induction
quiet environment
effective communication within the team
be sure sedation (including muscle relaxation) has taken full effect before administering induction drug (ketamine)
Induction
Advisable to administer a muscle relaxant before the induction agent
-GGE
-Benzodiazepine: diazepam or midazolam
Ketamine 2.2 mg/kg
Intubation
26mm diameter tube for average 500 kg horse mouth gag to pull jaws apart neck extended lubricate tube intubate blindly- easy inflate cuff
Positioning on theatre table
Depends on type of sx
cushion pressure points (head, shoulders, pelvis)
stretch and spread apart limbs- to encourage blood flow
Protect eyes from trauma, pressure
Turn while changing body positions slowly
Keep in only one lateral recumbency throughout
Maintenance
Isoflurane, sevoflurane
Large animal circle anesthetic circuit required
Oxygen flow rate: 20ml/kg/min soon after induction (30-60min) and towards recovery; 10ml/kg/min during maintenance
Mechanical ventilation (IPPV) recommended esp if anesthesia time longer than 45 min
IV drugs for partial or total anesthesia
Make use of local anesthetic drugs and techniques as much as possible
PIVA and TIVA
most IVA protocols in horses combine:
A2 adrenergic drugs (xylazine, detomidine, romifidine, medetomidine)
Muscle relaxant (GGE, midazolam)
Hypnotic agent (ketamine)
Maintenance PIVA
combination of inhalational and IV drugs attainment of balanced anesthesia Goals: MAC (inhalation agent) reduction Analgesia provision Vital system adverse effects reduction
Maintenance: TIVA advantages
Less cardio system depression
Superior analgesia
less likelihood of movement in response to surgical stimulus
decreased surgical stress
lower morbidity and mortality
better quality of recovery from anesthesia
TIVA: field maintenance
TIVA protocols commonly known as
Triple drips
Double drips effective as well
Include any possible local anesthetic techniques for maintenance
TIVA
alternatively top up with intermittent boluses
Ketamine about 0.4 mg/kg
Diazepam or midazolam 0.1 mg/kg
a2 adrenergic agonist (xylazine, deromidine, romifidine)
Monitoring
Anesthetic depth Resp Cardio Regular arterial blood gas Thermoregulatory
Anesthetic depth
CNS
Surgical: weak palpebral reflex/anal tone
too light: lacrimation, nystagmus, movement
Respiratory system
RR and depth (TV)
hypoventilation likely: IPPV mostly needed; asses ETCO2 (expired CO2)
