Objective—To examine stress-related neurohormonal
and metabolic effects of butorphanol, fentanyl, and
ketamine administration alone and in combination
with medetomidine in dogs.
Procedure—5 dogs received either butorphanol (0.1
mg/kg), fentanyl (0.01 mg/kg), or ketamine (10 mg/kg)
IM in a crossover design. Another 5 dogs received
either medetomidine (0.02 mg/kg) and butorphanol
(0.1 mg/kg), medetomidine and fentanyl (0.01 mg/kg),
medetomidine and ketamine (10 mg/kg), or medetomidine
and saline (0.9% NaCl) solution (0.1 mL/kg) in
a similar design. Blood samples were obtained for 6
hours following the treatments. Norepinephrine, epinephrine,
cortisol, glucose, insulin, and nonesterified
fatty acid concentrations were determined in plasma.
Results—Administration of butorphanol, fentanyl, and
ketamine caused neurohormonal and metabolic
changes similar to stress, including increased plasma
epinephrine, cortisol, and glucose concentrations. The
hyperglycemic effect of butorphanol was not significant.
Ketamine caused increased norepinephrine concentration.
Epinephrine concentration was correlated
with glucose concentration in the butorphanol and fentanyl
groups but not in the ketamine groups, suggesting
an important difference between the mechanisms
of the hyperglycemic effects of these drugs.
Medetomidine prevented most of these effects
except for hyperglycemia. Plasma glucose concentrations
were lower in the combined sedation groups
than in the medetomidine-saline solution group.
Conclusions and Clinical Relevance—Opioids or
ketamine used alone may cause changes in stressrelated
biochemical variables in plasma.
Medetomidine prevented or blunted these changes.
Combined sedation provided better hormonal and
metabolic stability than either component alone. We
recommend using medetomidine-butorphanol or
medetomidine-ketamine combinations for sedation or
anesthesia of systemically healthy dogs. (Am J Vet Res 2005;66:406–412)