Mesenteric artery response to head‐up tilt‐induced centralhypovolaemia and hypotension

Abstract
Superior mesenteric artery (SMA) blood flow and impedance were evaluated byduplex ultrasound during head‐up tilt (HUT)‐induced central hypovolaemia and hypotension ineight healthy volunteers. HUT induced a reduction in cardiac stroke volume from88·8±6·3 to 64·7±6·3 ml(mean±SEM; PPP−1) did not change significantly, although the end‐diastolic velocity increasedfrom 9·7±4·8 to 39·7±4·0 cm s−1 (PP=0·04) was accompanied by a ninefoldincrease in the end‐diastolic velocity (P<0·01). The results indicate areduction in the mesenteric vascular impedance to the extent that superior mesenteric artery bloodflow is maintained during HUT‐induced central hypovolaemia and hypotension.

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