Baroreceptor-mediated reduction of jejunal mucosal perfusion, evaluated with endoluminal laser Doppler flowmetry in conscious humans.

Reduction of central blood volume elicits a peripheral vasoconstrictor reflex in various tissues including skin, skeletal muscle and the hepatomesenteric region. The aim of the present study was to investigate whether this reaction includes a decreased perfusion of the jejunal mucosa in man. Laser Doppler flowmetry (LDF) was used to monitor jejunal mucosal and skin perfusion simultaneously in eleven healthy volunteers. LDF recordings were performed during quiescent (phase 1) periods of the migrating motor complex. Seven subjects demonstrated cycling changes of jejunal mucosal perfusion (vasomotion). The average minimum jejunal flux value was 72 +/- 6 perfusion units. The average intraindividual coefficient of variation was 18 +/- 2%. Lower body negative pressure (LBNP) was used to elicit controlled reductions of central blood volume. LBNP of 10 mm Hg induced a 12 +/- 4% (P < 0.05) decrease in jejunal perfusion and a 43 +/- 11 (P < 0.001) decrease in cutaneous perfusion. Corresponding responses to LBNP of 20 mm Hg were 17 +/- 5% (P < 0.01) and 37 +/- 10% (P < 0.01) reductions in jejunal mucosal and skin perfusion, respectively. Cardiac index was significantly reduced by the LBNP procedure, whereas heart rate remained unchanged and blood pressure changes were minor and inconsistent. These findings indicate that the reflex vasoconstriction induced by mild central hypovolemia includes a significant reduction of jejunal mucosal perfusion in supine resting humans. This reflex may provide one mechanism for the intestinal ischemia often occurring in critically ill patients.