Effects of pre-operative administration of medetomidine on plasma insulin and glucose concentrations in healthy dogs and dogs with insulinoma

Objective: To investigate the effect of medetomidine on plasma glucose and insulin concentrations in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery. Animals: Twenty-five dogs with insulinoma and 26 healthy dogs. Methods: In dogs with insulinoma, medetomidine (5 μg kg^-1) was randomly included (n = 12) or omitted (n = 13) from the pre-anesthetic medication protocol, which typically contained an opioid and an anticholinergic. Healthy dogs received medetomidine (5 μg kg^-1; n = 13) or acepromazine (0.04 mg kg^-1; n = 13) plus an opioid (morphine 0.5 mg kg^-1) and an anticholinergic (atropine 0.04 mg kg^-1) as pre-anesthetic medications. Pre-anesthetic medications were given intramuscularly. Plasma glucose and insulin concentrations were measured before (sample 1) and 30 minutes after pre-anesthetic medication (sample 2), and at the end of surgery in dogs with insulinoma or at 2 hours of anesthesia in healthy dogs (sample 3). Glucose requirement to maintain intra-operative normoglycemia in dogs with insulinoma was quantified and compared. Data were analyzed with anova and Bonferroni post-test, t-tests or chi-square tests as appropriate with p < 0.05 considered significant. Data are shown as mean ± SD. Results: Medetomidine significantly decreased plasma insulin concentrations and increased plasma glucose concentrations in healthy dogs and those with insulinoma. These variables did not change significantly in the dogs not receiving medetomidine. In the dogs with insulinoma, intra-operative glucose administration rate was significantly less in the animals that received medetomidine compared to those that did not. Conclusions: Pre-anesthetic administration of medetomidine significantly suppressed insulin secretion and increased plasma glucose concentration in dogs with insulinoma and in healthy dogs undergoing anesthesia and surgery. Clinical relevance: These findings support the judicious use of medetomidine at low doses as an adjunct to the anesthetic management of dogs with insulinoma.