EXPOSURE TO HIGH ENVIRONMENTAL-TEMPERATURE IN THE SAUNA DOES NOT CHANGE PLASMA INDOCYANINE GREEN (ICG) CLEARANCE IN HEALTHY-SUBJECTS

Indocyanine green (ICG) was given intravenously (0.5 mg kg(-1)) to sev en healthy male volunteers in random order during a control session an d a session in the sauna bath. The sauna bathing session consisted of three 10 min. stays in the sauna (temperature 85-95 degrees, relative humidity 25-30%), separated by two 5-min. periods of resting at 22 deg rees. Blood samples were taken for 60 min. in order to calculate ICG p lasma clearance (CI), volume of distribution (V-ss) and elimination ha lf-life (t(1/2 beta)). The mean+/-S.E.M. values of ICG plasma clearanc e, V-ss and t(1/2 beta) for the control session and the sauna bathing session were 0.47+/-0.08 1 min.-l versus 0.39+/-0.04 1 min.(-1), 2.4+/ -0.41 versus 2.3+/-0.2 1 and 3.9+/-0.3 min. versus 4.4+/-0.3 min., res pectively. No statistically significant differences in the CI, t(1/2 b eta) or V-ss of ICG were detected between the control and sauna bathin g sessions. The results suggest that short-term exposure to high ambie nt temperatures during sauna bathing does not affect hepatic blood flo w. Consequently, short-term hyperthermia and associated changes in hep atic blood flow are assumed to have little, if any, effect on the hepa tic clearance of drugs.