Estimation of rewarming time in transported extramural hypothermic neonates

To evaluate the time taken for rewarming hypothermic neonates and to correlate the time taken for rewarming with severity of hypothermia (WHO classification), weight, gestational age and associated morbidity.

100 extramural neonates transported to the Referral neonatal unit of a teaching hospital, with weight more than 1000 grams and abdominal skin temperature less than 36.5 oC at admission were included in the study. Hypothermia was classified as per WHO recommendations. Clinical features including age, weight, gestational age, clinical diagnosis and vitals were recorded at the time of admission. Rewarming was done under a servo-controlled radiant warmer, in skin mode at set temperature of 37 oC. Skin and air temperatures measured by the thermistor probe were recorded at the time of admission and then at least every 15 minutes till skin temperature reached 36.5 oC. The neonates were monitored for oxygen saturation, blood glucose and capillary filling time and stabilized promptly.

The mean abdominal skin temperature was 34.9 +/- 1.4 oC. 72% of babies were moderately or severely hypothermic as per WHO classification. The duration of rewarming was 4.9 +/- 0.8 min, 17.5 +/- 9.5 min and 42+/-7.9 min for mild, moderate and severe hypothermia respectively (p=0.021). The difference in rate of rewarming between various grades of hypothermia was also significant. The duration of rewarming a baby did not differ significantly between the different weight and gestational age groups. When the rate of rewarming was expressed as rise in oC per Kg body weight per hour, it was higher in smaller and more premature babies. The rate of rewarming was slower in asphyxiated babies.

The duration of rewarming depends on the severity of hypothermia. When rewarmed under radiant warmer using servo mode, the duration of rewarming a baby is the same irrespective of weight and gestational age. Asphyxiated babies take longer time to rewarm.