The impact of streptozotocin-induced diabetes on the minimum alveolar anesthetic concentration (MAC) of inhaled anesthetics in the rat.

We designed experiments to examine the effects of insulin-dependent diabetes mellitus on the anesthetic requirements for volatile anesthetics. A standard tail-clamp technique was used to determine minimum alveolar anesthetic concentrations for halothane, enflurane, and isoflurane in spontaneously breathing rats. Three groups of animals were used: 1) diabetic rats (12 wk after induction of diabetes with streptozotocin, 50 mg/kg, single dose, intravenously), 2) insulin-treated (7 U extended insulin zinc suspension per day, subcutaneously, beginning 5 wk after streptozotocin treatment) diabetic rats, and 3) control rats. The minimum alveolar anesthetic concentration values of the control animals were 1.16 +/- 0.02 vol% for halothane, 2.25 +/- 0.05 vol% for enflurane, and 1.42 +/- 0.04 vol% for isoflurane. Minimum alveolar anesthetic concentration was reduced by 23% for halothane (0.90 +/- 0.06 vol%), by 18% for enflurane (1.85 +/- 0.07 vol%), and by 17% for isoflurane (1.18 +/- 0.04 vol%) in diabetic rats. Insulin treatment restored the anesthetic requirement to control levels for all three anesthetics. These data from the rat model indicate that uncontrolled diabetes lowers anesthetic requirements significantly.