Duration of nonresponse to noxious stimulation after intramuscular administration of butorphanol, medetomidine, or a butorphanol-medetomidine combination during isoflurane administration in dogs.
OBJECTIVE
To assess duration of actions of butorphanol, medetomidine, and a butorphanol-medetomidine combination in dogs given subanesthetic doses of isoflurane (ISO).


METHODS
6 healthy dogs.


METHODS
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 microg/kg], and a combination of butorphanol [0.2 mg/kg] and medetomidine [5.0 microg/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, end-tidal 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.


CONCLUSIONS
During ISO-induced 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.
Grimm
K A
KA
Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana 61802, USA.
Tranquilli
W J
WJ
Thurmon
J C
JC
Benson
G J
GJ
D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage; D000701:Analgesics, Opioid / Q000008:administration & dosage; D019162:Anesthetics, Combined / Q000008:administration & dosage; D018685:Anesthetics, Inhalation; D000818:Animals; D001831:Body Temperature; D002077:Butorphanol / Q000008:administration & dosage; D018592:Cross-Over Studies; D004285:Dogs / Q000502:physiology*; D007273:Injections, Intramuscular / Q000662:veterinary; D007530:Isoflurane; D017214:Laryngeal Masks; D020926:Medetomidine / Q000008:administration & dosage; D011897:Random Allocation; D013623:Tail
D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D007530:Isoflurane; D020926:Medetomidine; D002077:Butorphanol