Blood flow changes during septic shock compared with controlled stepwise blood flow reduction in the superior mesenteric artery: effects on microcirculatory blood flow in the small intestine

Introduction

Splanchnic ischemia due to sepsis or hemorrhage is believed to be involved in the pathogenesis of multiple organ dysfunction syndrome. In previous studies performed in our laboratory we have studied microcirculatory blood flow of the small intestinal mucosa in a porcine model of septic shock [1]. We have demonstrated that microcirculatory blood flow (MBF) was redistributed from the jejunal muscularis towards the mucosa. The aim of this study was to measure changes in MBF in the jejunum during stepwise occlusion of the superior mesenteric artery (SMA).

Methods

Data from the sepsis group have been extracted from a previously published study [1]. Swiss landrace pigs (30 kg) were anesthetized and mechanically ventilated. Cardiac output (CO) was measured using thermodilution and SMA flow with ultrasonic transit time flowmetry. MBF was measured in the jejunal mucosa and muscularis using laser Doppler flowmetry. In the septic shock group (group S, n = 11), sepsis was induced by fecal peritonitis. In the SMA occlusion group (group O, n = 8), SMA flow was reduced in steps of 15% using an occluder.

Results

Results are presented as percent of baseline (mean ± SD, *P < 0.05 compared with baseline, ^†P < 0.05 mucosa vs muscularis). During septic shock, the CO, SMA flow and MBF of jejunal muscularis decreased to 56 ± 13%*, 47 ± 13%* and 36 ± 17%*^†, respectively, while the MBF in jejunal muscularis remained virtually unchanged (86 ± 20%^†). In nonseptic animals, stepwise occlusion of the SMA to 42 ± 4%* of baseline produced a decrease of muscularis blood flow to 43 ± 12%*^† while mucosal blood flow decreased less, to 65 ± 24%*^†.

Conclusion

During reduced regional blood flow, microcirculatory flow decreased less in the intestinal mucosa than in the muscularis, suggesting redistribution of flow away from the muscularis towards the mucosa, both in septic and in nonseptic subjects. Blood flow redistribution appeared to be more pronounced in septic than in nonseptic animals.