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
Objective—To evaluate the effects of butorphanol
and carprofen, alone and in combination, on the minimal
alveolar concentration (MAC) of isoflurane in
Design—Randomized complete-block crossover
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
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)