Lecture 14 10/29/24 Flashcards
What are the indications for chemical restraint in horses?
-standing surgery
–skin laceration repair
–enucleation
–ovariectomy
–sinusotomy
-diagnostics
–endoscopy
–radiography
What are the benefits of using chemical restraint in horses?
-lower risk of complications
-lower cost
-less time
What are the disadvantages of using chemical restraint in horses?
-danger to animal
-danger to personnel
-less than ideal surgical conditions
-insufficient analgesia
What are the characteristics of the ideal chemical restraint agent?
-small volume
-water soluble
-non-irritant to tissues
-no pain on injection
-rapid onset of action
-non-toxic
-absence of adverse effects
-compatible with other agents
What is the preferred approach to chemical restraint?
combination of drugs/multimodal approach
Which components of history and physical exam are important to consider for anesthesia?
-age
-size and body condition
-drug sensitivities
-concurrent diseases
What are the characteristics of anesthetic drug administration?
-typically given IV
-IV drugs given slowly
-complications if drugs are given perivascular or intra-arterial
-IM possible, but lower bioavailability and slower onset of action
What are the cardiovascular effects of acepromazine?
-minimal affects on cardiac output and heart rate
-hypotension
-anti-arrhythmic
What are the pros of using acepromazine in horses?
-widely available
-muscle relaxation
-small volume
-augments opioid sedation
-few adverse effects
-inexpensive
What are the cons of using acepromazine in horses?
-no analgesia
-slow onset of action
-sedation may persist for several hours
-inconsistency in sedative response
-penile protrusion
What are the effects of opioids on the cardiovascular system?
-bradycardia
-hypotension
What are the effects of opioids on the CNS?
-analgesia
-sedation
-possible excitement
What are the effects of opioids on the resp. system?
-resp. depression
-decreased sensitivity of resp. center to CO2
-hypoventilation
What are the effects of opioids on the GI tract?
non-propulsive intestinal motility/ileus with high doses
What are the clinical uses of opioids?
-provide sedation with alpha2 agonists for standing restraint
-premedication prior to general anesthesia
-epidural analgesia
What are the characteristics of benzodiazepine use in horses?
-mainly for co-induction with ketamine
-minimal CV and resp. side effects
-muscle relaxation
-sedation in foals
-anticonvulsants
What are the pros of alpha2 adrenoceptor agonist use in horses?
-dose-dependent sedation, analgesia, and muscle relaxation
-reversible
What are the cons of alpha2 adrenoceptor agonist use in horses?
-cardiac and resp. depression
-sedated animal may react to noise/stimuli
-causes ileus
-metabolic effects; diuresis, hypoinsulinemia, hyperglycemia, sweating
What are the characteristics of clinical sedation with alpha2 adrenoceptors?
-head lowers
-ataxia; more severe with detomidine and xylazine
-degree and duration of sedation is dose and drug dependent; romifidine > detomidine > xylazine
What are the signs of detomidine sedation?
-lowering of the head
-drooping of lip
-relaxation of penis
-base-wide stance
What are the delivery methods for standing sedation drug combinations?
-single injection
-infusion
What are the characteristics of combining alpha2 agonists with opioids?
-more reliable sedation than alpha2 alone
-less likelihood of sudden reaction to stimuli
-give alpha2 agonist first to sedate, then opioid
-dose adjustments may be needed
What are the characteristics of alpha2 reversal?
-cardiorespiratory compromise can occur with alpha2 overdose
-reverse to shorten the prolonged sedation of high dose alpha2s
-reverse the GI effects of alpha2s
Why are local/regional blockades used?
increase the efficacy of standing sedation
Which local blocks are used in horses?
-line-field
-nerve
-regional/epidural
Which nerve blocks are used around the eye?
-auriculopalpebral (eyelid)
-supraorbital
Which vertebrae are used as landmarks when given an epidural?
coccygeal 1 and coccygeal 2
Why are epidurals given between the coccygeal vertebrae?
to prevent blockage of the femoral nerve and allow the horse to remain standing
