Effectiveness of forced air warming after pediatric cardiac surgery employing hypothermic circulatory arrest without cardiopulmonary bypass

Study Objective: To evaluate the effectiveness of forced-air warming compared to radiant warming in pediatric cardiac surgical patients recovering from moderate hypothermia after perfusionless deep hypothermic circulatory arrest. Design: Prospective unblinded study. Setting: Teaching hospitals. Patients: 24 Pediatric cardiac surgical patients. Intervention: Noncyanotic patients undergoing repair of atrial or ventricular septal defects were cooled by topical application of ice and rewarmed initially in the operating room by warm saline lavage of the pleural cavities. On arrival at the intensive care unit (ICU), patients were warmed by forced air (n = 13) or radiant heat (n = 11). The time, heart rate, and blood pressure at each 0.5°C increase in rectal temperature were measured until normothermia (36.5°C) to determine the instantaneous rewarming rate. Measurements and Main Results: Baseline characteristics were not different in the two groups. The mean (± SD) age was 5.6 ± 3.4 years, weight was 20 ± 8 kg, esophageal temperature for circulatory arrest was 25.7 ± 1.3°C, and duration of circulatory arrest was 25 ± 11 minutes. The mean core temperature on arrival at the ICU was 29.9 ± 1.3°C and ranged from 26.1 to 31.5°C. The mean rewarming rate for each 0.5°C was greater (p < 0.05) for forced-air (2.43 ± 1.14°C/hr) than radiant heat (2.16 ± 1.02°C/hr). At core temperatures <33°C, the rewarming rate for forced-air was 2.04 ± 0.84°C/hr and radiant heat was 1.68 ± 0.84°C/hr (p < 0.05). At core temperatures ≥ 33°C, the rewarming rate for forced air was 2.76 ± 1.20°C/hr and radiant heat was 2.46 ± 1.08°C/min (p = 0.07). Significant determinants of the rewarming rate in a multivariate regression model were age (p < 0.001), temperature (p < 0.05), time after arrival to the intensive care unit (p < 0.05), pulse pressure (p < 0.05) and warming device (p < 0.001). The duration of ventilatory support and ICU length of stay was not different in the two groups. Conclusions: Both forced-air and radiant heat were effective for rewarming moderately hypothermic pediatric patients. When core temperature was less than 33°C, the instantaneous rewarming rate by forced air was 21% faster than by radiant heat.