[Respiratory gas exchange during total body hyperthermia in man]

Respiratory gas exchange was evaluated using indirect calorimetry during total body hyperthermia (TBH) in 7 postoperative patients with disseminated gastric cancer to the peritoneal cavity. TBH was induced using veno-venous bypass and extracorporeal circuit incorporating a heat exchanger to keep pulmonary arterial temperature 42 degrees C. The high temperature was maintained for 3 hours under general anesthesia with droperidol (0.15 mg.kg-1), morphine (1 mg.kg-1) and enflurane (less than 0.5%). Oxygen consumption (VO2) was also calculated using the Fick equation and thermodilution cardiac output. Hyperthermia for three hours increased both VO2 and carbon dioxide output (VCO2) values to 1.5 times as compared to the control values before heating, respectively. VO2 values measured by indirect calorimetry correlated well with the values calculated from the Fick equation when respiratory and cardiovascular system were relatively stable during the procedure. Gradual but statistically insignificant increase in respiratory quotient was observed after recooling started. These results suggest that indirect calorimetry was valuable to measure respiratory gas exchange continuously during hyperthermic state as well as normothermic state. However, RQ value observed in the present study may be modified by several factors including lactate accumulation in the blood, and may not reflect substrate utilization during the hyperthermic state.