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Duration of nonresponse to noxious stimulation after intramuscular administration of butorphanol, medetomidine, or a butorphanol-medetomidine combination during isoflurane administration in dogs

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  • 1 Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.
  • | 2 Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.
  • | 3 Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.
  • | 4 Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802.

Abstract

Objective—To assess duration of actions of butorphanol, medetomidine, and a butorphanol-medetomidine combination in dogs given subanesthetic doses of isoflurane (ISO).

Animals—6 healthy dogs.

Procedure—Minimum alveolar concentration (MAC) values for ISO were determined. for each dog. Subsequently, 4 treatments were administered to each dog (saline [0.9% NaCl] solution, butorphanol [0.2 mg/kg of body weight], medetomidine [5.0 mg/kg], and a combination of butorphanol [0.2 mg/kg] and medetomidine [5.0 mg/kg]). All treatments were administered IM to dogs concurrent with isoflurane; treatment order was determined, using a randomized crossover design. Treatments were given at 7-day intervals. After mask induction with ISO and instrumentation with a rectal temperature probe, endtidal CO2 and anesthetic gas concentrations were analyzed. End-tidal ISO concentration was reduced to 90% MAC for each dog. A tail clamp was applied 15 minutes later. After a positive response, 1 of the treatments was administered. Response to application of the tail clamp was assessed at 15-minute intervals until a positive response again was detected.

Results—Duration of nonresponse after administration of saline solution, butorphanol, medetomidine, and butorphanol-medetomidine (mean ± SD) was 0.0 ± 0.0, 1.5 ± 1.5, 2.63 ± 0.49, and 5.58 ± 2.28 hours, respectively. Medetomidine effects were evident significantly longer than those for saline solution, whereas effects for butorphanol-medetomidine were evident significantly longer than for each agent administered alone.

Conclusion and Clinical Relevance—During ISOinduced anesthesia, administration of medetomidine, but not butorphanol, provides longer and more consistent analgesia than does saline solution, and the combination of butorphanol-medetomidine appears superior to the use of medetomidine or butorphanol alone. (Am J Vet Res 2000;61:42–47)

Abstract

Objective—To assess duration of actions of butorphanol, medetomidine, and a butorphanol-medetomidine combination in dogs given subanesthetic doses of isoflurane (ISO).

Animals—6 healthy dogs.

Procedure—Minimum alveolar concentration (MAC) values for ISO were determined. for each dog. Subsequently, 4 treatments were administered to each dog (saline [0.9% NaCl] solution, butorphanol [0.2 mg/kg of body weight], medetomidine [5.0 mg/kg], and a combination of butorphanol [0.2 mg/kg] and medetomidine [5.0 mg/kg]). All treatments were administered IM to dogs concurrent with isoflurane; treatment order was determined, using a randomized crossover design. Treatments were given at 7-day intervals. After mask induction with ISO and instrumentation with a rectal temperature probe, endtidal CO2 and anesthetic gas concentrations were analyzed. End-tidal ISO concentration was reduced to 90% MAC for each dog. A tail clamp was applied 15 minutes later. After a positive response, 1 of the treatments was administered. Response to application of the tail clamp was assessed at 15-minute intervals until a positive response again was detected.

Results—Duration of nonresponse after administration of saline solution, butorphanol, medetomidine, and butorphanol-medetomidine (mean ± SD) was 0.0 ± 0.0, 1.5 ± 1.5, 2.63 ± 0.49, and 5.58 ± 2.28 hours, respectively. Medetomidine effects were evident significantly longer than those for saline solution, whereas effects for butorphanol-medetomidine were evident significantly longer than for each agent administered alone.

Conclusion and Clinical Relevance—During ISOinduced anesthesia, administration of medetomidine, but not butorphanol, provides longer and more consistent analgesia than does saline solution, and the combination of butorphanol-medetomidine appears superior to the use of medetomidine or butorphanol alone. (Am J Vet Res 2000;61:42–47)