Sympathetic Vasoconstrictor Responsiveness of the Leg Vasculature During Experimental Endotoxemia and Hypoxia in Humans.

Objective: Sympathetic vasoconstriction regulates peripheral circulation and controls blood pressure, but sepsis is associated with hypotension. We evaluated whether apparent loss of sympathetic vasoconstrictor responsiveness relates to distended smooth muscles or to endotoxemia and/or hypoxia. Design: Prospective descriptive study. Setting: Hospital research laboratory. Subjects: Ten healthy young men (age [mean +/- SD], 31 +/- 8 yr; body weight, 83 +/- 10 kg) participated in the study. Interventions: Leg blood flow and mean arterial pressure were determined, whereas leg vascular conductance was calculated during 1) adenosine infusion (vasodilator control), 2) hypoxia (FIO2 = 10%), 3) endotoxemia, and 4) endotoxemia + hypoxia. Leg sympathetic vasoconstrictor responsiveness (reduction in leg vascular conductance) was evaluated by femoral artery tyramine infusion. Measurements and Main Results: Endotoxemia increased body temperature from 36.9 +/- 0.4[degrees]C to 38.6 +/- 0.5[degrees]C (p

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