Splanchnic circulation

Abstract

The arterial supply to the splanchnic bed comprises three divisions of the abdominal aorta; the coeliac artery; and the superior and inferior mesenteric arteries. • Under physiological conditions, blood flow in the splanchnic circulation is controlled via intrinsic (myogenic and metabolic) and extrinsic (autonomic and humoral) mechanisms. • The splanchnic bed forms an important circulatory reservoir, which can be mobilized during periods of physiological stress. • Disorders of the splanchnic circulation may contribute to the multi-organ dysfunction syndrome and vice versa. • A number of techniques used in anaesthesia and critical care influence the distribution of blood flow in the splanchnic circulation. The splanchnic circulation is a complex system. A number of important functions depend on its normal operation, including digestion and absorption within the gut, maintenance of the mucosal barrier, and successful healing of surgical anastomoses, but we have little quantitative information about its physiology because routine measurement in humans is so difficult. This article outlines some basic science and describes how influential the splanchnic circulation might be in our clinical practice. Anatomy The term 'splanchnic circulation' describes the blood flow to the abdominal gastrointestinal organs including the stomach, liver, spleen, pancreas, small intestine, and large intestine. It comprises three major branches of the abdominal aorta; the coeliac artery; superior mesenteric artery (SMA); and inferior mesenteric artery (IMA) (Fig. 1). The hepatic portal circulation delivers the majority of the blood flow to the liver. Coeliac artery The coeliac artery is the first major division of the abdominal aorta, branching at T12 in a horizontal direction ∼1.25 cm in length. It shows three main divisions such as the left gastric artery, common hepatic artery, and splenic artery and is the primary blood supply to the stomach, upper duodenum, spleen, and pancreas. Superior mesenteric artery The SMA arises from the abdominal aorta anteriorly at L1, usually 1 cm inferior to the coeliac artery. The five major divisions of the SMA are the inferior pancreaticoduodenal artery, intestinal arteries, ileocolic, right colic, and middle colic arteries. The SMA supplies the lower part of the duodenum, jejunum, ileum, caecum, appendix, ascending colon, and two-thirds of the transverse colon. It is the largest of the splanchnic arterial vessels delivering >10% of the cardiac output and therefore has significant implications for embolic mesenteric ischaemia. Inferior mesenteric artery The IMA branches anteriorly from the abdominal aorta at L3, midway between the renal arteries and the iliac bifurcation. The main branches of the IMA are the left colic artery, the sigmoid branches, and the superior rectal artery. It forms a watershed with the middle colic artery and supplies blood to the final third of the transverse colon, descending colon, and upper rectum. Physiology Resting splanchnic blood flow (SBF) is typically 30 ml min −1 100 ...

Enhanced diastolic dysfunction but preserved systolic function after acute pressure overload in the absence of smoothelin-like 1 protein

“…The findings stress the importance of SMTNL1 deletion in advancing adverse cardiac responses to a hyperconstrictive vasculature. The splanchnic mesentery receives 10-40% of the cardiac output depending on digestion status (Harper and Chandler, 2016; Sun et al, 1992), and male Smtnl1 -/- mice possess significantly enhanced vasoconstriction of the mesenteric arteries that would contribute to elevated systemic vascular resistance (Turner et al, 2019). However, an earlier characterization of the Smtnl1 -/- animals is in disagreement since it did not reveal any alteration in peripheral blood pressure (Wooldridge et al, 2008).…”

“…Hence, the goal of this study was to assess the effect of SMTNL1 silencing on cardiac morphometry and hemodynamics in both male and female cohorts. Furthermore, resistance vessels are critical in the establishment and maintenance of blood pressure (Burton, 1954; Harper and Chandler, 2016); enhanced myogenic tone of vessels from SMTNL1 KO mice is suggestive of increased total peripheral resistance, which could lead to high blood pressure. For this reason, we also examined the effect of acute pressure-overload driven by transverse aortic constriction (TAC) on cardiac function and morphology in the absence of SMTNL1.…”

Superior mesenteric and renal flow patterns during intra‐aortic counterpulsation

“…This would be mediated through opening of mechanosensitive cation channels, principally Na + . The resulting depolarization would activate voltage‐gated Ca 2+ channels, elevating intracellular Ca 2+ concentrations, thereby inducing smooth muscle contraction (Harper & Chandler, ). This was confirmed by the evidence from our findings that when the total mesenteric flow was indexed by vascular resistance, it increased with the balloon on, showing an inverse relationship with resistances.…”

Iliocaval Venous Obstruction, Cardiac Preload Reserve and Exercise Limitation

“…It is known that at rest, 25% of the total cardiac output is distributed to the splanchnic bed [11], one of the largest reservoirs of unstressed blood volume. The splanchnic bed is richly innervated with adrenergic receptors which can respond rapidly to sympathetic stimulation [12].…”