DECREASED SPLANCHNIC PERFUSION MEASURED BY DUPLEX ULTRASOUND IN HUMANS UNDERGOING SMALL-VOLUME HEMORRHAGE

Objectives: To quantitate duplex Doppler measurements of splanchnic pe rfusion to determine if these measurements are reproducible in euvolem ic humans and if such measurements are sensitive to mild degrees of sy stemic hypovolemia. Design: Prospective, nonrandomized, controlled tri al. Setting: Clinical research center. Participants: Seven fasting, he althy male and female volunteers, ranging in age from 25 to 37 yrs and weighing 60 to 90 kg. Interventions: Pulse, blood pressure, hematocri t, and duplex Doppler measurements of the peak systolic velocity and t ime averaged velocity of the subdiaphragmatic aorta, celiac artery, an d superior mesenteric artery were obtained at four time points. Time p oints I and II were on separate days before hemorrhage and consisted o f routine blood donation of 450 mL. Time point III was immediately aft er blood donation. Time point IV was 24 hrs after donation. Estimated blood flow was calculated from time averaged velocity (estimated blood flow = 60[vessel cross-sectional; area][time averaged velocity]). Mea surements and Main Results: Vital signs and hematocrit remained withou t significant change at all time points. Peak systolic velocity, time averaged velocity, and estimated blood flow were also unchanged betwee n measurements at time points I and II. However, after a mean reductio n of 9.1% of total blood volume, duplex ultrasound detected significan t decreases of 14.5% in celiac artery and superior mesenteric artery p eak systolic velocity, as well as 15.1%, 17.3%, and 20.2% decreases in aorta, celiac artery and superior mesenteric artery time averaged vel ocity and estimated blood flow, respectively (all values p < .05 vs. b aseline, Duncan's multiple range test). All measured variables returne d to baseline 24 hrs after hemorrhage. Conclusions: Noninvasive duplex Doppler measurements of splanchnic peak systolic velocity, time avera ged velocity, and estimated blood flow are reproducible and sensitive to small changes in intravascular volume. These data suggest a potenti al clinical role for duplex imaging in the treatment of critically ill patients to guide therapy to optimize splanchnic perfusion.