Predictors of hypothermia during spinal anesthesia

Background: Body temperature often is ignored during regional anesthesia, d espite evidence that hypothermia occurs commonly. Because hypothermia is as sociated with adverse clinical outcomes, it is important to recognize predi ctors of hypothermia and to monitor and control body temperature in patient s at risk. The current study was designed to determine the predictors of co re hypothermia in patients receiving spinal anesthesia for radical retropub ic prostatectomy. Methods: Forty-four patients undergoing radical retropubic prostatectomy we re studied. A lumbar intrathecal injection of 18-22 mg bupivacaine, 0.75%, with 20 mu g fentanyl was given. No active warming measures were used other than intravenous fluid warming. The following clinical variables were asse ssed as potential predictors of core (tympanic) temperature at admission to the postanesthesia care unit: duration of surgery, average ambient operati ng room temperature, body habitus, age, and spinal blockade level. Results: The mean core temperature at admission to the postanesthesia care unit was 35.1 +/- 0.6 degrees C (range, 33.6-36.3 degrees C). Duration of s urgery, ambient operating room temperature, and body habitus were not predi ctors of hypothermia. A high level of spinal blockade and increasing :Ige w ere predictors of hypothermia. For each incremental increase in block level , core temperature decreased by 0.15 degrees C, and for each increase in ag e, core temperature decreased by 0.3 degrees C. Conclusions: Although high-level spinal blockade has been associated with d ecreased thermoregulatory thresholds, no previous study has shown that a hi gher level of blockade is associated with a greater magnitude of core hypot hermia in the clinical setting. As with general anesthesia, advanced age is associated with hypothermia during spinal anesthesia.