Temperature gradients in pigs during whole-body hyperthermia at 42 degrees C

Temperature was simultaneously measured by thermistors in multiple deep-body and peripheral sites in adult pigs heated continuously at 42 degrees C (rectal) and above for 4-24 h. During hyperthermia, the relations between different body temperatures were maintained and up to 1.0 degrees C separated temperature measurements at sites such as liver and bone marrow. These persistent temperature gradients must be borne in mind when evaluating tumor response in patients subjected to whole-body heating for disseminated cancer. Temperatures recorded by rectal, deep esophageal, or tympanic membrane sensors provided a reliable index of core temperature (including brain temperature) under equilibrium conditions at 42 degrees C, but only esophageal and tympanic sensors could safely be used to monitor the induction phase of hyperthermia and the adjustive changes in body-heat content required to stabilize core temperature during sustained hyperthermia. Pigs withstood repeated heating at 42 degrees C for 6 h, and recovered rapidly, but died after 24 h of hyperthermia. Pigs subjected to unrestrained heating died at 45 degrees C (esophagus).