The effect of head covering on rewarming and shivering in cardiac surgical patients

Abstract

In hypothermic postoperative cardiac surgical patients, heat loss from the head may interfere with rewarming and cause shivering. This study investigated the effect of head covering on rewarming rate and shivering during post-operative rewarming. The sample included 19 experimental and 21 control subjects. The heads of experimental subjects were wrapped with two terry cloth towels until urinary bladder temperature (UBT) reached 37 degrees C. Admission UBTs were mildly hypothermic (34.6 degrees C to 36.70 C). Four experimental and six control subjects shivered. There were no significant differences (P < .05) in the incidence of shivering (Yates' chi 2 = 0.33; P = 0.855). After controlling significant differences between groups in height and body surface area with analysis of covariance, there were no significant differences in rewarming rate (F = 3.270; P = .079). Shiverers were slightly colder (mean, 36.13 degrees C; t = 1.768; P = .085) on admission to the cardiac surgical intensive care unit and had significantly greater heat gain (t = -2.091, P = .043) than nonshiverers. Conclusions about the effect of head covering on shivering could not be made because of small sample size. Failure to demonstrate a significant difference in rewarming rate is due to the effects of mildly hypothermic admission UBTs on the mathematical calculation of rewarming rate and on the small sample size.