ANESTHESIA OF NORTH-AMERICAN RIVER OTTERS (LUTRA-CANADENSIS) WITH MEDETOMIDINE-KETAMINE AND REVERSAL BY ATIPAMEZOLE

North American river otters (Lutra canadensis) were anesthetized in co operation with an otter restoration program administered by the North Carolina Wildlife Resources Commission during winter 1993. Five doses of medetomidine (10, 25, 50, 75, and 100 mug/kg, i.m.) in combination with ketamine (2.5 mg/kg, i.m.) were evaluated in 41 river otters. Hea rt rate and rhythm, respiratory rate, rectal temperature, relative oxy hemoglobin saturation, systolic, diastolic, and mean arterial blood pr essures were monitored at 5-min intervals for 30 min. Otters were anes thetized at all but the lowest dose (medetomidine 10 mug/kg-ketamine 2 .5 mg/kg), which produced heavy sedation of short duration. We recomme nd medetomidine 25 mug/kg combined with ketamine 2.5 mg/kg, i.m., in r iver otters for anesthetic induction prior to inhalation anesthesia or for short procedures, including minor surgery. A higher dose of medet omidine (50 mug/kg) in combination with ketamine (2.5 mg/kg) is requir ed for procedures of 25 min or longer, but respiratory depression may occur. Atipamezole (50-200 mug/kg, i. m.) reversed the effects of mede tomidine-ketamine in otters. Total recovery time was shorter with high er doses of atipamezole relative to the medetomidine dose, and a ratio of 4:1 (atipamezole: medetomidine) worked best in these trials.