Protection in rats with heatstroke: Hyperbaric oxygen vs activated protein C therapy

The present study was attempted to evaluate the therapeutic effects of activated protein C and/or hyperbaric oxygen in an animal model of heatstroke. Sixty-eight minutes heat stress (43°C) initiated, the anesthetized rats were randomized to several groups and administered: 1) no resuscitation (vehicle solution plus normabaric air, 2) intravenous activated protein C (1. mg in 1. ml of normal saline per kg of body weight), 3) hyperbaric oxygen (100% oxygen at 202. kpa for 17. min), and 4) intravenous activated protein C plus hyperbaric oxygen. Another group of rats exposed to room temperature (26°C) was used as normothermic controls. Blood sampling was 0. min, 70. min, and 85. min after heat stress initiated. When the vehicle-treated rats underwent heat exposure, their survival time values found were to be 19-25. min. Resuscitation with activated protein C or hyperbaric oxygen significantly and equally improved survival during heatstroke (134-159. min). As compared with those of activated protein C or hyperbaric oxygen alone, combined activated protein C and hyperbaric oxygen significantly had higher survival time values (277-347. min). All vehicle-treated heatstroke animals displayed systemic response, hypercoagulable state, and hepatic and renal dysfunction. Combined activated protein C and hyperbaric oxygen therapy reduced these heatstroke reactions better than activated protein C or hyperbaric oxygen alone. The results indicate consequently, combined activated protein C and hyperbaric oxygen therapy heightens benefit in combating heatstroke reactions.