Effect of increasing central venous pressure during passive heating on skin blood flow

Whole body heating in humans increases skin blood flow (SkBF) and decreases central venous pressure (CVP). This study sought to identify whether eleva tions in SkBF are augmented during passive heating if CVP is increased duri ng the heat stress. Seven subjects were exposed to passive heating. Once Sk BF was substantially elevated, 15 ml/kg warm saline were rapidly infused in travenously. Whole body heating significantly increased cutaneous Vascular conductance and decreased CVP from 7.7 +/- 0.6 to 4.9 +/- 0.5 mmHg (P < 0.0 5). Saline infusion returned CVP to pre-heat-stress pressures (7.9 +/- 0.6 mmHg; P > 0.05) and significantly increased cutaneous Vascular conductance relative to the period before saline administration. Moreover, saline infus ion did not alter mean arterial pressure, pulse pressure, or esophageal tem perature (all P > 0.05). To serve as a volume control, 15 ml/kg saline were rapidly infused intravenously in normothermic subjects. Saline infusion in creased CVP (P < 0.05) without affecting mean arterial pressure, pulse pres sure, or cutaneous vascular conductance (all P > 0.05). These data suggest that cardiopulmonary baroreceptor unloading during passive heating may atte nuate the elevation in SkBF in humans, whereas loading cardiopulmonary baro receptors in normothermia has no effect on SkBF.