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  • Author or Editor: Douglas N. Lange x
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in Journal of the American Veterinary Medical Association


Objective—To evaluate effects of medetomidine on anesthetic dose requirements, cardiorespiratory variables, plasma cortisol concentrations, and behavioral pain scores in dogs undergoing ovariohysterectomy.

Design—Randomized, prospective study.

Animals—12 healthy Walker-type hound dogs.

Procedure—Dogs received medetomidine (40 µg/kg [18.2 µg/lb] of body weight, IM; n = 6) or saline (0.9% NaCl) solution (1 ml, IM; 6) prior to anesthesia induction with thiopental; thiopental dose needed for endotracheal intubation was compared between groups. Ovariohysterectomy was performed during halothane anesthesia. Blood samples were obtained at various times before drug administration until 300 minutes after extubation. Various physiologic measurements and end-tidal halothane concentrations were recorded.

Results—In medetomidine-treated dogs, heart rate was significantly lower than in controls, and blood pressure did not change significantly from baseline. Plasma cortisol concentrations did not increase significantly until 60 minutes after extubation in medetomidine-treated dogs, whereas values in control dogs were increased from time of surgery until the end of the recording period. Control dogs had higher pain scores than treated dogs from extubation until the end of the recording period.

Conclusion and Clinical Relevance—Administration of medetomidine reduced dose requirements for thiopental and halothane and provided postoperative analgesia up to 90 minutes after extubation. Dogs undergoing ovariohysterectomy by use of thiopental induction and halothane anesthesia benefit from analgesia induced by medetomidine administered prior to anesthesia induction. Additional analgesia is appropriate 60 minutes after extubation. (J Am Vet Med Assoc 2000;217:509–514)

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in Journal of the American Veterinary Medical Association


Objective—To evaluate the effects of butorphanol and carprofen, alone and in combination, on the minimal alveolar concentration (MAC) of isoflurane in dogs.

Design—Randomized complete-block crossover study.

Animals—6 healthy adult dogs.

Procedure—Minimal alveolar concentration of isoflurane was determined following administration of carprofen alone, butorphanol alone, carprofen and butorphanol, and neither drug (control). Anesthesia was induced with isoflurane in oxygen, and MAC was determined by use of a tail clamp method. Three hours prior to induction of anesthesia, dogs were fed a small amount of canned food without any drugs (control) or with carprofen (2.2 mg/kg of body weight [1 mg/lb]). Following initial determination of MAC, butorphanol (0.4 mg/kg [0.18 mg/lb], IV) was administered, and MAC was determined again. Heart rate, respiratory rate, indirect arterial blood pressure, endtidal partial pressure of CO2, and saturation of hemoglobin with oxygen were recorded at the time MAC was determined.

Results—Mean ± SD MAC of isoflurane following administration of butorphanol alone (1.03 ± 0.22%) or carprofen and butorphanol (0.90 ± 0.21%) were significantly less than the control MAC (1.28 ± 0.14%), but MAC after administration of carprofen alone (1.20 ± 0.13%) was not significantly different from the control value. The effects of carprofen and butorphanol on the MAC of isoflurane were additive. There were not any significant differences among treatments in regard to cardiorespiratory data.

Conclusion and Clinical Relevance—Results suggest that administration of butorphanol alone or in combination with carprofen significantly reduces the MAC of isoflurane in dogs; however, the effects of butorphanol and carprofen are additive, not synergistic. (J Am Vet Med Assoc 2000;217:1025–1028)

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in Journal of the American Veterinary Medical Association