Antilipopolysaccharide improves survival in primates subjected to heat stroke

Recent investigations have suggested that endotoxins or lipopolysaccharides (LPS) may play a role in heat stroke pathophysiology. In this study we wish to investigate whether prophylactic administration of anti-LPS hyperimmune plasma improves survival of experimental heat stroke in primates. Eleven monkeys were anesthetised and heat-stressed to a rectal temperature of 43.5 degrees C (group A) and then allowed to recover at room temperature. Five had received a prophylactic i.v. dose of equine anti-LPS (experimental group), while the other six (control group) received an equivalent i.v. dose of nonimmune equine plasma. All the experimental monkeys survived, while only one out of the six controls survived (chi 2 = 4.65, p less than 0.025). All the control animals that succumbed had significantly elevated plasma LPS levels (p less than 0.05) as compared to the experimental group and the single surviving control. The latter showed very little or no change in plasma LPS levels. A further eight monkeys (group B) were heat-stressed to a rectal temperature of 43.8 degrees C. Of these eight, four had received a prophylactic i.v. dose of equine anti-LPS plasma. Although all eight animals died, the four which were pretreated with anti-LPS plasma had a significantly longer survival time (427.5 +/- 61.39 min) than the untreated group (81.25 +/- 33.94 min) (p less than 0.05). Furthermore, the plasma LPS levels in the treated monkeys remained unchanged whereas in the untreated group, a significantly elevated plasma LPS level was noticed (p less than 0.005). We conclude that LPS may have a role in heat stroke pathophysiology and that prophylactic treatment with anti-LPS antibodies would seem to offer protection against the effects of heat stress.