Draft Horse Anesthesia Flashcards
How does laryngeal paralysis affect intubation? How can this be avoided? What is another option for intubation?
increases risk of difficult intubation —> have several sizes available and use an endoscope
nasal intubation with a cuffed ET tube lubricated with phenylephrine + curvet stylet and backup oral tubes
What anesthetic risk is especially draft horses? What is it associated with?
post-operative myopathy
anesthetic mortality due to increased risk of long bone fractures in recovery
What are 3 risk factors to developing post-operative myopathy? How can this be avoided?
- poor padding and positioning
- prolonged anesthetic duration
- hypotension
maintain peripheral perfusion and oxygen delivery
What contributes to cardiac output? MAP?
HR and SV
CO x SVR = MAP
What are the 2 major determinants of skeletal muscle perfusion?
- hydrostatic pressure within vessel
- compression of the skeletal muscle body mass/external weight
What 3 aspects of anesthesia decrease skeletal muscle perfusion and lead to post-anesthetic myopathy?
- inhalants = vasodilation + negative inotropy = hypotension
- PPV = increased intrathoracic pressure = hypotension
- dependent limbs compressed under the body due to positioning
What is the goal to avoiding hypotension? In what 4 ways can this be done?
increasing cardiac output
- maintain HR
- maintain contractility by decreasing inhalants and infusing dobutamine
- maintain preload with IV fluid bolus
- maintain SVR by decreasing inhalants and infusin phenylephrine
What affects oxygen delivery to organs? SV?
oxygen content (CaO2) x CO
preload x afterload (SVR) x contractility
What is the main cause of anesthetic hypoxemia in draft horses? In what 5 ways can it be managed?
compression of thorax by abdominal contents = compression atelectasis —> V/Q mismatch
- monitor SpO2, arterial blood gas, and lactate
- monitor FiO2
- recruitment maneuvers - temporary airway pressure is increased during mechanical ventilation
- PEEP valve
- nasal insufflation of O2 in recovery
How does draft horse anesthetic drug doses compare to other horses?
allometrically scaled down
What is the major concern with draft horse recovery? In what 2 ways can this be avoided?
ataxia and decreased strength increases risk of recovery morbidity —> want a rapid recovery with strong, coordinated attempts
- minimize total inhalants - desflurane instead of isoflurane?
- reverse sedation with Flumazenil to hasten elimination of recovery drugs and Tolazoline shortly before standing
How can recovery be made safer for draft horses?
- provide oxygen insufflation
- foam mattress (extra thick)
- proper limb positioning
- draft sling
- large hobbles
What is the proper limb position to avoid post-operative myopathy?
- keep legs parallel to floor and support limbs
- keep dependent limb pulled forward
What are 4 options for controlling surgical pain in draft horses?
- steroid - Dexamethasone
- NSAIDs - Phenylbutazone, Flunixin meglumine
- opioid - butorphanol
- alpha-2 agonist - Xylazine, Detomidine, Dexmedetomidine
What prep and induction is commonly used for draft horses?
PREP:
- Xylazine IV - minimal sedation
- Detomidine IV - calm
INDUCTION:
- Xylazine IV - good sedation
- Ketamine + Midazolam IV
