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

Objectives: To quantitate duplex Doppler measurements of splanchnic perfusion to determine if these measurements are reproducible in euvolemic humans and if such measurements are sensitive to mild degrees of systemic hypovolemia. Design: Prospective, nonrandomized, controlled trial. Setting: Clinical research center. Participants: Seven fasting, healthy male and female volunteers, ranging in age from 25 to 37 yrs and weighing 60 to 90 kg. Interventions: Pulse, blood pressure, hematocrit, and duplex Doppler measurements of the peak systolic velocity and time averaged velocity of the subdiaphragmatic aorta, celiac artery, and superior mesenteric artery were obtained at four time points. Time points I and II were on separate days before hemorrhage and consisted of routine blood donation of 450 mL. Time point III was immediately after 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]). Measurements and Main Results: Vital signs and hematocrit remained without significant change at all time points. Peak systolic velocity, time averaged velocity, and estimated blood flow were also unchanged between measurements at time points I and II. However, after a mean reduction of 9.1% of total blood volume, duplex ultrasound detected significant decreases of 14.5% in celiac artery and superior mesenteric artery peak systolic velocity, as well as 15.1%, 17.3%, and 20.2% decreases in aorta, celiac artery and superior mesenteric artery time averaged velocity and estimated blood flow, respectively (all values p < .05 vs. baseline, Duncan's multiple range test). All measured variables returned to baseline 24 hrs after hemorrhage. Conclusions: Noninvasive duplex Doppler measurements of splanchnic peak systolic velocity, time averaged velocity, and estimated blood flow are reproducible and sensitive to small changes in intravascular volume. These data suggest a potential clinical role for duplex imaging in the treatment of critically ill patients to guide therapy to optimize splanchnic perfusion.