Hypothermia following acute carbon-monoxide poisoning increases mortality

The effect of body temperature during recovery from acute severe carbon monoxide (CO) poisoning on morbidity and mortality was investigated using an unanesthetized animal model. Levine prepared female rats were exposed to 2700 ppm CO for 90 min, displaying the usual hypothermia, hypotension and bradycardia. Body temperature in survivors was either maintained at the terminal CO exposure value for 4 h ('cooled'), rapidly raised to the pre-CO exposure value for 4 h ('heated') or allowed to return to normal naturally ('unheated'). Following this period of recovery, the 'heated' rats sustained the lowest mortality rate (22%), the 'unheated' rats a greater mortality rate (44%), and the 'cooled' rats the highest mortality rate (50%). Inclusive of the surviving rats, there were no significant differences in neurologic deficit between the three groups, after 4, 24 or 48 h of recovery. Aside from a significant delay in recovery of blood pressure in the 'heated' rats relative to the other two treatment groups post-CO, there were no differences in blood pressure, heart rate or plasma glucose. The results suggest that rapid return to euthermia improves survival following acute severe CO poisoning, contrasting with an earlier study showing the detrimental effect of euthermia during CO poisoning.