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123 Cards in this Set
- Front
- Back
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What are the 3 option available for equine anesthesia?
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-standing sedation
-field anesthesia -inhalational anesthesia |
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Under which conditions is standing sedation used?
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-high risk cases facing non-elective procedures
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Drugs used for standing sedation almost always cause what in stallions?
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Penile relaxation
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TIVA is used for which type of equine procedures?
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-procedure less than 1 hour in duration
-castration |
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Inhalational anesthesia is used for procedure slonger than 1 hour in duration, such as what?
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- colic sx
-arthroscopy |
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Which type of equine anesthesia is the least stressful for the animal?
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Field anesthesia
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What is the quick formula for estimating the weight of a horse?
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Weight (kg) = girth x length/ 660
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What is the most common drug combination for equine standing sedation?
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A2 agonist + opioid
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How should the head be positioned during standing sedation?
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Head should be above the level of the heart to promote venous drainage
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What condition can result if the head is not elevated?
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Facial & nasal edema
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Nasal & facial edema are most common with which drug?
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Detomidine
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Which 3 A2 agonists are used for standing sedation of the equine?
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-xylazine
-detomidine -romifidine |
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Which A2 reversal agent can be used if a problem arises with giving A2's?
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Atipamezole
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What effects do opioids, given alone to a healthy horse, have?
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Stimulates, rather than sedates them
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What effects do opioids have when given with A2 agonists?
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-enhance the sedative effect of A2, without causing CNS stimulation
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Which opioid is never given IV?
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Pethidine- tachycardia, hypotension, urticarial reaction from histamine release
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What effect does ACE have on horses?
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Highly variable
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Blood pressure can stay depressed for how long after giving ACE?
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6-8 hours
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Why would you add ACE to an A2 agonist and opioid combination?
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Enhances their effects, lowering the dose needed
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Why are BZD's never used alone for equine sedaiton?
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Induces profound skeletal muscle relaxation causing ataxia, stumbling & disorientation which horses find distressing
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BZD's are useful as sedation and pre-med in which age of horse?
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Sick foals where ataxia is easy to handle
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BZD's are used in combination with what other drug for equine induction?
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Ketamine
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Diazepam reacts with other drugs except for which one?
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Ketamine
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What is the benefit of using midazolam?
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Give be mixed in the same syringe
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What is the classic combination doe standing sedation for equine castration?
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Xylazine plus Butophanol
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Which drug can be administered by CRI for prolonged standing procedures?
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Detomidine
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What other anesthetic drugs should be given when using Detomindine CRI?
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Local anesthetic blocks or epidural
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At the completion of standing sedation, what should you do before leading the horse from the stocks?
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Try to waken them
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If a pregnant must be sedated, which drug would you choose?
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ACP- no specific uterine effects or fetal CV effects (minimal)
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Why is xylazine contra-indicted in the last trimester of pregnancy in cows?
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Stimulates uterine contraction
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In sick foals, the preferred choice of sedation is what?
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BZD's supplemented by opioids
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How would you try to orally sedate an unmanageable horse?
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ACO, detomidine sugar cube
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How effective is oral sedation?
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Not very, drug bioavailability is lowered
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What technique can be used to IM injection on unmanageable horses?
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Remote IM with an IV tubing set
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Which drugs are preferred for IM sedation of unmanageable horses?
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Detomidine + butorphanol
or morphine + ACP |
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Following IM injection, how long should the animal remain unstimulated?
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20 minutes
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What are the indications for epidural analgesia in horse?
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-peri-operative analgesia for arthoscopy, perineal/vulva sx, sever hindlimb injuries or fx
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In conditiosn such as fx, lacerations, septic arthritis, whats a useful method of delivering epidrual analgesia?
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Epidural catheter
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Analgesia of the stifle requires that the anesthetic solution move to where?
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Cranially to the spinal cord segment L4
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Where are epidural injection performed on the equine?
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Sacrococcygeal or
C1-C2 intercoccygeal junction |
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What drugs are commonly used for epidurals?
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-opioids
-A2 agonists |
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Are local anesthetics recommended?
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Not in large doses
-use ropivicaine -low caudal procedures |
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What is the overall mortality rate of horse undergoing GA?
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0.9-1.6%
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What are the 3 GA options available for anesthetizing horses?
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-field anesthesia with bolus top ups
-TIVA -IV induction followed by inhalational agent |
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The preliminary anesthesia exam will help determine which method to use and includes evaluation of what factors?
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-physical status of pt
-duration of anesthesia -number and skill of personnel -safety of facility/location -anesthetic/monitoring equipment available |
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What is an "over the door" exam?
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Evaluating the horses temperament, metation, general condition and attitude while in the stall
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Should you be concerned about a second degree AV block in a healthy horse?
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No- my be a physiological finding, see if it disappears after he's excercised
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When would peri-operative blood work be needed?
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-prior to colic sx
-in animals that have sustained severe nosebleeds |
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Which horse types are a higher anesthetic risk?
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Large heavy horses
Nervous excitable horses |
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Fit athletic horses run a higher risk of what condition post anesthesia?
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Myopathy
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Larger horses have a higher risk of myositis which is due to what?
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Duration of recumbency
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True or False. It is better to underdose a horse then to over dose a horse.
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False, better to over dose
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Why is under dosing more of a problem?
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Horse may panic, flounder and thrash about
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Do older or younger horses respond better to ACP?
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Younger
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How should very fit horse be prepared for anesthesia?
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Let down for 10 days prior, ending training and stopping hard feed
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In preparation for GA, why is the horse starved for 12-18 hours?
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Minimize effects of gastric distension on FRC
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What other preparation should be made?
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-remove shoes or wrap
-wrap legs -protect eyes -wash out mouth |
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What approach do you take if, after several doses of A2 agonists, the horse is still not responding?
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Come back another day
(leave some ACP for administration prior to your next arrival) |
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Prior to GA induction, every horse must have what placed?
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IV catheter
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Horse must not be induced until they are profoundly sedated. What are the signs of profound sedation?
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-lowered head
-wide base stance -weight-shifting ataxia -tembling lips -drooping eyelids "head to knees, ketamine please" |
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What is the default premedication induction drug combination for horses?
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A2 agonist + Ketamine/Diazepam
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How long is the period of anesthesia with this combination?
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1-15 mins
total down time 20-30 be ready with top up |
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What are the drug options for top up?
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-Thiopentone
-A2 (xylazine, ketamine) -BZD |
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Why is the advamtage to using thiopentone as a top up drug?
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Most rapid onset of action
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What is the disadvantage to using Thiopentone as a top up?
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-may induce apnea
(avoided by slow injection) |
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What dose of xylazine or ketamine is given as a top up?
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1/2 to 1/3 of the induction dose
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What is the advantage of using xylazine or ketamine as a top up?
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-recovery quality is not diminished
-no CVS depression with cumulative dosage |
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When do xylazine and ketamine work best as a top up?
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Only if given before the animal becomes too light
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Topping up can increase the time of anesthesia to how long?
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1 hour
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What top up drugs are used if Romifidine or detomidine are used for induction?
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None...don't top up
romifidine and detomidine are long acting |
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In choosing a BZD for a top up drug, why would you select Midazolam over Diazepam?
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Midazolam can be mixed in a syrunge with other drugs (ketamine)
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What are the benefits of using TIVA?
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-for procedures 1 hour or less in duration
-safer than inhalational -smoother recovery |
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What is the difference between using top ups and CRI or TIVA?
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Less swings in the plane of anesthesia
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Most CRI and TIVA techniques are based on what drug combination for horses?
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GGE, ketamine and A2 agonist- Triple Drip
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What TIVA protocol has been used on horses but in the OR?
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Propofol, fentanyl, medetomindine
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In horses what is the maximum concentration of GGE that should be used?
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No stronger than 10%
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How should GGE be administered?
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By IV catheter and then flushed
Massive inflammatory response if injected perivascularly, can cause thrombophlebitis |
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What pre meds are given prior to GGE?
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A2 agonists
GGE is given until the horse is ataxic and then a bolus of thio or ketamine |
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What are the features of using GGE for induction?
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-reduces dose of induction agent for high risk cases
-requires assistant and crush -highly irritant if injected extravascularly -can cause hemolysis & phlebitis |
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Is the triple drip infusion rate constant throughout the procedure?
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No, start at a high rate, reduce to a maintenance rate
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is O2 given with Triple Drip
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If available, by a small soft rubber tube via nasal insufflation
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How are the signs of triple drip anesthesia different then when using other drugs?
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-horse appears very light
-palbebral reflex is very active -may be nystgamus, ear movement or occasional swallowing |
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What are the paradoxical signs of overdose with Triple Drip?
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-forelimbs undergo extensor rigidity
-opisthotonic when in lateral position |
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When changing the infusion rate of triple drip, is the response immediate?
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No, should run at the increased rate for 30 seconds, surgery should stop and wait for an additional minute
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What are the overall advantages to using triple Drip for horses?
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-versatile for field anesthesia
-minimal equipment -non-violent response to sz -good analgesia -no ET tube -maintains good blood gas figures if O2 given |
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What are the major disadvantages to using Triple Drip?
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-weakness after prolonged admin
-difficult to monitor, may be difficult to control -overdose possible;non-linear dosing -needs dedicated anesthetist |
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What results would you see with a mistaken intra-carotid injection in a horse?
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Rapid, violent induction, followed by convulsions
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What treatment should be given in the case of carotid injection?
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-IV anticonvulsants such as diazepam, or any anesthetic agent, O2, PPV may protect against brain injury as well as steroids and furosemide
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Inadvertent carotid catherization can also lead to what conditions?
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-cerebral embolism
-massive swelling of the neck |
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What are the signs of anesthetic under-dosage?
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-struggling
-sever in-coordination -marked excitement or violence |
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What reaction is seen if the Ketamine is injected before the A2 agonist?
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Excitement, rigidity, hyperasthesia
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Is Post induction apnea benign?
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Yes, no concern if it occurs just after induction
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Apnea that occurs during sx can mean what?
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-impending death, or recovery
-may precede cardiac arrest or indicate it has already occured |
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What steps do you take if breathing does not return in 2 minutes?
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-manually twist larynx
-tread on larynx -twist the ear -kick the ribs -kick the diaphragm -dilate rectum -Doxapram 1mgkg as final option |
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How do you define bradycardia during sx?
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-HR < 22
-poor pulse -discolored MM -hypercoaguable blood ate surgery site |
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What drugs are given to treat bradycardia?
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-atropine
-dobutamine -adrenaline |
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Cyanosis during anesthesia can be caused by what?
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Possible bradycardia, low CO, respiratory distress
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What is the most common intra-operative cardiac arrhythmia seen?
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Atrial premature depolarization
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Which arrhythmias are common post induction with an A2 agonist?
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First & second degree AV block
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When is nasotracheal intubation useful?
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Induction of foals and for inhalational maintenance for dental sx or other intra-oral procedures
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In preparing for inhalational anesthesia, what important step is take to protect the eyes?
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Plenty of eye lubrication
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What is a common reason that a horse will try to stand prematurely during recovery?
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Full bladder, cath and empty prior to sx
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What type of anesthesia system is used for inhalatonal agents for horses?
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Large circle system w/ O2 and N2O if atrerial blood gas analysis is available
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What are the most common CRI drugs given during inhalational anesthesia for horses?
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-ketamine
-fentanyl -medetomidine -lidocaine |
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What is the metabolic O2 requirement for a horse?
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5mlkg/min
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Occular reflexes on horse are less dependable for monitoring anesthesia. What should you look for?
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tension of the strap muscles of the neck
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What are some of the standard monitoring methods used during GA of horses?
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-capnograph
-ECG -direct arterial blood pressure -blood gas analysis |
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Where should a horse be placed to recover from GA?
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Quiet, cushioned box
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What steps should be taken to ensure a safe recovery?
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-O2 by nasal insufflation
-cover eyes with towel -ensure quiet breathing |
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What should you do if the horse attempts to stand prematurely?
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Low dose of A2 agonist
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What is considered a key contributing factor to the high perioperative mortality rate of horses undergoing GA?
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Cardiovascular depression
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Intra-operative hypotension is treated with what type of drugs?
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Inotropes
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What is the most common inotrope used?
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Dobutamine
(ephedrine) |
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What is one of the best methods to avoid hypoxia esp in a dorsal recumbent horse?
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Positive pressure ventilation
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What are some of the causes of hypoxemia?
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-recumbency
-hypoventilation -progressive atelectasis -RL interpulmonary shunting -VQ mismatching -reduced cardiac output -effects of anesthesia on the protective hypoxic pulmonary vasoconstriction response (HPV) |
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What factors predispose a horse to hypoxemia?
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-duration of anesthesia
-size & conformation -body position -IPPV or spontaneous ventilation -depth of anesthesia -factors lowering FRC- preg, hobbling, feeding -drugs affecting HPV |
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What makes maintaining a stable plane of anesthesia more difficult in a horse?
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-marked individual variation
-slow response to changes in anesthetic depth -difficulty in assessing depth |
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How can you reduce the risk of recovery injury such as a fx?
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Low dose of A2 agonist during recovery
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What are the 2 common causes of stretorous breathing after GA of the horse?
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-nasal edema and swelling of the nasal turbinates
-epiglottic eversion |
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What is EPAM?
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Equine Post Anesthetic Myositis
-a sporadic problem producing signs ranging from transient lameness to generalized myositis |
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What are the primary predisposing factors of EPAM?
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-prolonged recumbency
-poor positioning -prolonged hypotension -muscle tension |
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How is EPAM treated?
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-analgesia (nsaids, opioids)
-fluid tx -encouraging the horse to walk -steroids |
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What are the common causes of neurapraxia and neuropathies?
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-handlers fail to prevent the face from hitting the ground during induction
-nerve is compressed for a long time -radial nerve paralysis may follow prolonged recumbency, pressure on the lower limb mimics myositis |
