Physiological effects of three inhalant anesthetics on Arctic ground squirrels

Restraint of small mammals may be necessary for procedures such as attachin g radiocollars or collecting blood samples. Additionally, when manual restr aint is not sufficient, chemical restraint may be required to prevent injur y to the animal and to the handler. However, the responses of mammals to ch emical restraint are often either unknown or species-specific. We compared effects of 3 inhalant anesthetics (halothane, isoflurane, and methoxyfluran e) and manual restraint on induction and recovery time, stress response, an d hematological parameters in Arctic ground squirrels (Spermophilus parryii ) in a field setting. Forty squirrels were live-trapped, randomly assigned to treatments, and released after recovery. Methoxyflurane ((x) over bar+/- SE: 69.3+/-5.9 sec) had a greater induction time (ANOVA, P<0.001) than halo thane and isoflurane, but isoflurane (19.5+/-1.8) and halothane (9.2+/-0.8) did not differ. All anesthetics differed (P<0.001) in recovery times: meth oxyflurane (198.0+/-21.0) had the slowest recovery time, isoflurane was int ermediate (124.7+/-2.95), and halothane was the most rapid (66.4+/-5.95). T ime to immobilize and collect the blood sample with manual restraint took a bout twice as long (116.4+/-11.4). Mean free cortisol levels (range: 81.5-9 1.8 nmol/L), glucose levels (range: 80.3-94.7 mg/dl), and hematocrits (rang e: 40.4-42.2%) were similar in all treatments; maximum corticosteroid bindi ng capacity was greater (P<0.05) in squirrels anesthetized with halothane ( 125.8+/-3.87 nmol/L) than in other treatments (range: 100.3-118.8). We reco mmend using methoxyflurane for field use when portable anesthetic units are not accessible.