Mesenteric, coeliac and splanchnic blood flow in humans during exercise

Abstract

1. Exercise reduces splanchnic blood flow, but the mesenteric contribution to this response is uncertain. 2. In nineteen humans, superior mesenteric and coeliac artery flows were determined by duplex ultrasonography during fasting and postprandial submaximal cycling and compared with the splanchnic blood flow as assessed by the Indocyanine Green dye-elimination technique. 3. Cycling increased arterial pressure, heart rate and cardiac output, while it reduced total vascular resistance. These responses were not altered in the postprandial state. During fasting, cycling increased mesenteric, coeliac and splanchnic resistances by 76, 165 and 126 %, respectively, and it reduced corresponding blood flows by 32, 50 and 43 % (by 0.18 +/- 0.04, 0.42 +/- 0.03 and 0.60 +/- 0.04 l min-1). Postprandially, mesenteric and splanchnic vascular resistances decreased, thereby elevating regional blood flow, while the coeliac circulation was not influenced. Postprandial cycling did not influence the mesenteric resistance significantly, but its blood flow decreased by 22 % (0.46 +/- 0.28 l min-1). Coeliac and splanchnic resistance increased by 150 and 63 %, respectively, and the corresponding regional blood flow decreased by 51 and 31 % (0.49 +/- 0.07 and 0.96 +/- 0.28 l min-1). Splanchnic blood flow values assessed by duplex ultrasound and by dye-elimination techniques were correlated (r = 0.70; P < 0.01). 4. During submaximal exercise in humans, splanchnic resistance increases and blood flow is reduced following a 50 % reduction in the hepato-splenic and a 25 % reduction in the mesenteric blood flow.

Figure 1. Cardiovascular variables during fasting semisupine rest, cycling and 2 min after termination of cycling

Values are means ±s.e.m. Continuous line, SMA; dotted line, CA. ^, different from rest, P < 0.05; •, different from the preceding value, P < 0.05. MAP, mean arterial pressure; CO, cardiac output; HR, heart rate; TVR, total systemic vascular resistance; SBF, splanchnic blood flow; SR, splanchnic vascular resistance; TAMV, time-averaged mean velocity; Diam, diameter; BF, blood flow; R, resistance.

Figure 2. Cardiovascular variables during fasting semisupine rest, postprandial (pp) semisupine rest, postprandial cycling and 2 min after termination of cycling

Values are means ±s.e.m. Continuous line, SMA; dotted line, CA. ^, different from pp, P < 0.05; •, different from the preceding value, P < 0.05. Abbreviations as for Fig. 1.

Figure 3. SBF measurements

A, splanchnic blood flow obtained by the dye-elimination technique (SBF-ICG) and duplex ultrasound (SBF-DU) at rest, after a meal and during postprandial cycling (n = 8). B, agreement in blood flow assessment: difference between dye-elimination technique and duplex ultrasound values (SBF-ICG - SBF-DU) plotted against average SBF values ((SBF-ICG + SBF-DU)/2). s.d., standard deviation; BF, blood flow. Mean ± 2 s.d. defines the 95% limits of agreement.