Effect of low-dose ketamine on redistribution hypothermia during spinal anesthesia sedated by propofol

Mild hypothermia is a common complication during spinal anesthesia and may induce a serious adverse outcome. We investigated the effect of low-dose ketamine infusion on the core temperature during spinal anesthesia sedated by propofol infusion. Twenty patients who were scheduled to undergo spinal anesthesia were assigned to one of two groups: after intrathecal injection of bupivacaine, patients who received infusion of ketamine (0.3 mg/kg/hr) and propofol (initial rate of 10 mg/kg/hr) (KP group), and patients who received infusion of placebo (saline) and propofol (initial rate of 10 mg/kg/hr) (P group). The rate of propofol administration was reduced as much as possible while maintaining sedation with an OAA/S score of 3 or below. The core temperature, forearm temperature, and fingertip temperature were recorded before spinal anesthesia, and just before (baseline) and 15, 30, 45, and 60 minutes after the start of propofol administration. The core temperature, reduction in core temperature from baseline (delta CT), and forearm-fingertip temperature gradient were compared between the two groups. In the P group, the core temperature linearly decreased over time. The core temperature at 30, 45, and 60 minutes was significantly higher in the KP group than in the P group (36.3 +/- 0.2 and 35.9 +/- 0.3, at 60 minutes, mean +/- SD, p < 0.05). The delta CT at 15, 30, 45, and 60 minutes was significantly smaller in the KP group than in the P group. There were no significant differences in the forearm-fingertip temperature gradient between the two groups over the study period. In conclusion, low-dose ketamine administration may confer thermoprotection during spinal anesthesia sedated by propofol.