Effects of hydration on endotoxin-induced temperature responses in rabbits

When a febrile illness is complicated by dehydration, thermoregulatory responses are often altered. Loss of body fluid volume may decrease blood volume, attenuate sweating, and decrease blood flow to the skin. Reduced skin blood blow may lessen the rate of heat transfer from body core to the environment. Fever treatment traditionally involves efforts to encourage a high oral intake of fluids by patients or administration of parenteral fluids. Despite the high frequency use of this nursing intervention during fever, the effectiveness of fluid administration has not been evaluated. In view of the recent discovery of the antipyretic activity of the pituitary hormone vasopressin, it is possible that dehydration has a beneficial role. Dehydration may enhance endogenous antipyresis by stimulating vasopressin release, making aggressive fluid replacement during fever undesirable.; This study examined the effects of body water status on the febrile response in endotoxin-injected rabbits. In addition, the study examined the effects of four hydration states (euhydrated, dehydrated, hyperhydrated and rehydrated) on cardiovascular and hydration measures during fever. Eight New Zealand White rabbits ranging in weight from 1.9 to 2.9 kg were studied in all experiment sets of this study.; The following conclusions were drawn from this study: (1) Fever response to endotoxin was greater in dehydrated than euhydrated rabbits indicating that activation of antipyretic mechanisms in dehydrated rabbits was not sufficient to reduce body core temperature, (2) Fever response to endotoxin was similar in eubydrated and hyperhydrated rabbits indicating that fluid administration did not alter the febrile response, (3) Fever response to endotoxin in the dehydrated state was lower when the animal was given fluid supplementation than when not given fluids indicating the possibility that activation of antipyretic mechanisms of AVP in rehydrated rabbits was sufficient to reduce body core temperature, and (4) Fluid supplementation appears to have a beneficial role in keeping body temperature lower.