Effects on C3 and CH50 levels during and following extracorporeal whole body hyperthermia

Cardiopulmonary bypass can affect inflammatory reactions and evoke the "postperfusion syndrome," manifested as multiple organ dysfunction in the recovery period. This syndrome is generated by the activation of complement, macrophages, neutrophils, and inflammatory cytokines. Following the use of hypothermia during cardiac procedures, active hyperthermic rewarming is used to reestablish body temperature. Complement levels and their interactions have been investigated during and following hypothermia. Hyperthermia is being used clinically; however, the effect of markedly elevated temperatures on complement is unknown and, therefore, needs to be investigated. A pilot canine study was designed to begin to explore what role hyperthermia may play on complement levels during and following extracorporeal whole body hyperthermia. Five dogs were heated to a core temperature of approximately 42 degrees C, held at this elevated temperature for 90 minutes, then cooled to normothermia. A decline in C3 levels at the end of warming with further declines through day 4 post treatment was observed. CH50 levels mimicked the C3 level decline; however, there was a trend for rebounding by day 4. The findings involving complement factors following hyperthermia signify that this increase in temperature causes a decrease in both C3 and CH50 levels.