Postoperative hypothermia and blood loss after the neonatal arterial switch procedure

Numerous studies have demonstrated that mild hypothermia helps reduce hypoxic/ischemic brain injury that may occur during neonatal cardiac procedures. However, traditional intensive care practices emphasize aggressive rewarming, and the risk of excessive bleeding that may be related to hypothermia.

An analysis was conducted of prospectively collected temperature and blood loss data on 47 neonates (30 boys, 17 girls) with transposition of the great arteries who underwent an arterial switch operation at median age 6 days (range, 2 to 23 days) and a mean weight of 3.6 +/- 0.6 kg. Blood loss was compared between 26 patients with mean temperatures below 35.5 degrees C for first 6 hours after operation (mild hypothermia group) and 21 patients at 35.5 degrees C or higher (normothermia group). Repeated-measures analysis of variance and regression modeling were used to evaluate the association between temperature and blood loss and to detect outliers.

Total postoperative blood loss was 31 +/- 28 mL in the first 6 hours and 61 +/- 37 mL at 24 hours (range, 15 to 238 mL). Postoperative blood loss between two groups at 6 or 24 hours did not differ significantly. After two outliers were removed, no significant relationship remained between body temperature at 6 hours and cumulative blood loss at 24 hours.

Mild postoperative hypothermia does not increase blood loss in neonates after the arterial switch operation. Lack of a difference between the two groups is not likely due to the study being underpowered. We recommend avoidance of aggressive rewarming, which might exacerbate potential neurologic injury.