Rapid plasma volume restoration increased skin sympathetic nerve activity component synchronized with cardiac cycle and cutaneous vasodilation in hypovolemic and passively warmed men

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We have suggested in passively warmed men that skin sympathetic nerve activity (SSNA) involved a component synchronized with cardiac cycle, the component increased as esophageal temperature (Tes) increased, but the increase was suppressed by hypovolemia with reduced cutaneous vasodilation. However, it remained unknown if rapid plasma volume (PV) restoration increased/recovered the component and cutaneous vasodilation. Fourteen young men with ~13% hypovolemia with a diuretic, were divided into 2 groups; time control (n=7, TC) and rapid infusion (n=7, RI). Subjects were warmed for 80min by infusing 47‐°C water into a perfused suit, while Tes, SSNA (microneurography; the peroneal nerve), skin blood flow (SkBF; laser‐Doppler flowmetry; the dorsal foot), and mean arterial pressure (MAP) were measured. After 50‐min warming, the component and cutaneous vascular conductance (CVC=SkBF/MAP) increased (all P<0.0001) as Tes rose by ~0.5°C. Then, when 37‐°C saline was infused at 0.7ml/min/kg for 30min in RI so that PV was restored to the baseline, the component and CVC rose by 17% and 10%, respectively, compared with before infusion in RI (all P<0.03) and the increases were higher than those in TC where saline was infused at 0.1ml/min/kg (all P<0.01). Thus, rapid PV restoration in hypovolemic hyperthermia recovered the component and cutaneous vasodilation.