PREANESTHETIC SKIN-SURFACE WARMING REDUCES REDISTRIBUTION HYPOTHERMIACAUSED BY EPIDURAL BLOCK

Redistribution of heat from the core to the cool peripheral compartmen ts of the body causes hypothermia during epidural anesthesia. Diminish ing the temperature gradient between the core and peripheral tissues b y warming the body via the skin before anesthesia should prevent this hypothermia. We measured core temperature, skin temperatures, and cuta neous heat loss in seven volunteers who received two lidocaine epidura l injections during a single study day. One epidural injection was giv en after the volunteer had rested in a cool room (almost-equal-to 22-d egrees-C) (''no prewarming'') for 2 h, and one injection was given aft er the volunteer had been covered with a forced air warming mattress ( almost-equal-to 38-degrees-C) (''prewarming'') for 2 h. Skin temperatu res were higher after prewarming. The decrease in core temperature dur ing epidural anesthesia was smaller after prewarming [mean within pati ent difference (prewarming-no prewarming): 0.41; P = 0.003]. However, heat loss was greater after prewarming (mean within patient difference : 26.4; P = 0.02). Shivering was less after prewarming. We conclude th at prewarming decreases redistribution hypothermia caused by epidural block. These results support the hypothesis that redistribution of hea t within the body, not heat loss, is the most important etiology of hy pothermia from epidural anesthesia.