Published online by Cambridge University Press: 02 September 2010
To evaluate passive and active methods for rewarming hypothermic lambs, the rectal temperature of 19 neonatal lambs (4·9 (s.e. 0·34) kg) was reduced to 35°C by cold water immersion. Metabolic responses and change in rectal temperature were monitored as the hypothermic lambs recovered with added insulation in a 20 to 25°C air environment, or with thermal assistance provided by an infrared heat lamp, or through immersion in 38°C water. During the first 12 min of rewarming, the rise in rectal temperature in all treatment groups was linear, however it was more rapid with the lambs immersed in warm water (0·26°C/min; P < 0·05) as compared with the insulated lambs (0·21°C/min) and the lambs rewarmed with a heat lamp (0·22°C/min). During this 12-min period, the insulated lambs produced metabolic heat more rapidly than did the warm-water lambs, 13·6 v. 11·1 (s.e. 0·67) W/kg, respectively (P < 0·05). These data indicate that there was a substantial influx of heat which contributed to the increase in body temperature of the lambs immersed in warm water. Stabilization of rectal temperature occurred after 18 to 20 min in all treatment groups. The lambs recovered in all treatment groups, in addition, no clinical problems were observed in any of the lambs during the tests or subsequently when they were returned to their dams.