Evaluation of analgesia and cardiorespiratory effects of epidurally administered butorphanol in isoflurane-anesthetized dogs.
OBJECTIVE
To determine variations in minimal alveolar concentration (MAC) of isoflurane and analgesic and cardiorespiratory effects of lumbosacral epidural administration of 0.25 mg of butorphanol/kg of body weight in dogs.


METHODS
16 healthy male dogs.


METHODS
Dogs were anesthetized with isoflurane alone. Eight dogs received butorphanol (group B) and the others an equal volume of isotonic saline solution (group S) administered by a catheter inserted in the lumbosacral epidural space. Isoflurane MAC was determined before and 30 minutes after the epidural injection, along with noxious stimulation to the fore- and bind limbs. Cardiorespiratory variables were recorded prior to and until 120 minutes after epidural administration. At that time, isoflurane anesthesia was ended, and nociception (toe pinch and pin-prick responses) was evaluated for 7 hours. Dogs were observed for 3 days to determine presence of neurologic side effects.


RESULTS
For group-B dogs, isoflurane MAC decreased by 31 +/- 8.6% after butorphanol was administered Cutaneous insensitivity (to pin-prick nociceptive test) persisted for 3 hours after the end of isoflurane anesthesia in group-B dogs. No response was observed to toe pinch stimulation for 80 minutes after anesthesia.


CONCLUSIONS
Epidural administration of 0.25 mg of butorphanol/kg in dogs was safe; minimal cardiorespiratory and no neurologic side effects were observed, and analgesia and an isoflurane-sparing effect were apparent.


CONCLUSIONS
The short duration of action of epidurally administered butorphanol limits its value for clinical practice.
Clinical Sciences Department, Faculte de Médcine Vétérinaire, Université de Montréal, Quzbee, Canada.
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Cuvelliez
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Blais
D015360:Analgesia, Epidural / Q000662:veterinary*; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D018685:Anesthetics, Inhalation; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002077:Butorphanol / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000097:blood; D004285:Dogs; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D007530:Isoflurane; D008297:Male; D010100:Oxygen / Q000097:blood; D011650:Pulmonary Alveoli / Q000378:metabolism; D012119:Respiration / Q000187:drug effects*; D014018:Tissue Distribution
D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D002245:Carbon Dioxide; D007530:Isoflurane; D002077:Butorphanol; D010100:Oxygen