Blood Volume Redistribution During Cross-Clamping of the Descending Aorta

Abstract

We tested the hypothesis that occlusion of the descending aorta is associated with blood volume redistribution resulting in a relative hypervolemia in organs and tissues proximal to the level of occlusion. The study was performed on splenectomized dogs anesthetized with pentobarbital. Whole body scintigraphy with a Sophy DSX rectangular large field of view gamma-camera equipped with a high resolution collimator was used; Tc99m was used to label plasma albumin. The aorta was occluded at diaphragmatic and suprarenal levels in random order. The activity was counted during different stages of the experiments in the following regions of interest: brain, left and right ventricles, left and right lungs, left and right deltoid muscles, the liver, and intestines. Cross-clamping at the suprarenal level was not associated with significant changes in blood volume in any region of interest. The aortic cross-clamping at diaphragmatic level was associated with significant increases in the gamma-emission in all organs and tissues above the level of aortic occlusion by 8%-38%. Thus, the present study supports the hypothesis by demonstrating that cross-clamping of the aorta at diaphragmatic level is associated with an increase in blood volume in the organs and tissues proximal to the level of cross-clamping. Such an increase might represent the mechanism for well-documented increases in preload and blood flow above aortic occlusion, resulting in an additional (in addition to an increase in afterload) burden to the heart.

Guidelines for the Early Management of Patients With Acute Ischemic Stroke

“…Data from animal models and from human research demonstrate that aortic occlusion, which is commonly performed by crossclamping the descending aorta for vascular control during aortic surgery, results in net flow diversion to the cerebral from the lower-extremity circulatory beds, thereby increasing cerebral blood flow. [707][708][709][710][711][712][713][714][715] This evidence generated the development of a catheter-based device with 2 balloons near its distal tip placed in the infrarenal and suprarenal positions in the descending aorta (NeuroFlo device; CoAxia, Maple Grove, MN). After insertion via the femoral artery, the balloons are inflated sequentially up to ≈70% of the diameter of the aortic lumen over a period of 45 minutes to an hour, followed by removal.…”

Changes in Hemodynamics and Acid-Base Balance during Cross-Clamping of the Descending Thoracic Aorta

“…In a previous study we demonstrated that the thermodilution technique is reliable for measuring CO during thoracic aortic XC [9] . The basic mechanism behind the increase in CO could be volume displacement from the splanchnic circulation to the relatively non-compliant upper part of the body, increasing preload and activating the Frank-Starling mechanism [10] . Another contributing mechanism for the increase in CO is probably a stimulation of the sympathetic nervous system due to ischemia distal to the aortic clamp, with increased release of catecholamines [11][12][13][14] .…”

Preoperative Inhibition of Angiotensin-Converting Enzyme Improves Systemic and Renal Haemodynamic Changes During Aortic Abdominal Surgery

“…First, mechanical occlusion of the aorta directly increases cardiac afterload whereas activation of the sympathetic nervous system and the RAS results in increased arteriolar vasomotor tone and myocardial contractility. Second, using radioisotopic techniques, it has been shown that blood volume is redistributed from the lower body to the more compliant splanchnic compartment [17]. Third, decreased right ventricular end-diastolic volume has been reported, despite unchanged cardiac filling pressures, suggesting lower cardiac preload associated with reduced ventricular diastolic compliance [18].…”