Prophylactic corticosteroid increases survival in experimental heat stroke in primates

It has been suggested that endotoxins or lipopolysaccharides (LPS), may contribute to heat stroke pathophysiology. In this study, 11 anesthetised monkeys were divided into 2 groups. The steroid group (n = 5) had received a dose of MPSS (30 mg.kg-1, i.v.) before being heat-stressed and the control animals (n = 6) received saline equivolumetrically. The animals were heat-stressed to a rectal temperature of 43.5 degrees C in an environmental temperature of 41 +/- 0.3 degrees C and 100% relative humidity and then allowed to recover at room temperature. Blood samples for LPS and anti-LPS IgG analyses were taken both before treatment and before and after heat-stress. The administration of prophylactic MPSS increased the survival rate significantly from 33% to 100% (p less than 0.05). The plasma LPS level in the steroid group showed very little change after heat-stress, whereas in the non-surviving controls there was a significant increase in plasma LPS level (from 0.089 +/- 0.007 to 0.257 +/- 0.031 ng.ml-1) (p less than 0.005). The control animals that survived showed very little increase in plasma LPS levels, but had about 300% greater plasma Anti-LPS IgG levels. We conclude that pretreatment with MPSS improves the survival rate during heat stroke, possibly by suppressing the rise in plasma LPS concentration.