Hemodynamic effects of aortic occlusion during hemorrhagic shock

We investigated cardiac dynamics following temporary aortic occlusion during profound hypovolemia and abdominal distention. Control animals (N = 10) were bled from a femoral artery catheter to a systolic blood pressure of 60 mm Hg, while simultaneous abdominal distention was effected with intraperitoneal infusion of saline. After one hour of shock, thoracic aortic occlusion and immediate laparotomy were performed. The aorta was clamped for 20 minutes and then released over 5 minutes. The second group (N = 10) underwent the same procedure but received methylprednisolone sodium succinate intravenously at the time of aortic occlusion. During hypotension, mean arterial pressure, cardiac output, stroke volume, and stroke work decreased, while systemic vascular resistance increased. Aortic occlusion improved cardiac hemodynamics in the control group; in the steroid group these changes were even more pronounced. Measurement of dp/dt demonstrated ventricular contractility impaired during hypotension and improved during the period of aortic occlusion. Temporary thoracic aortic occlusion in the face of profound hypotension and massive abdominal distention improved cardiac function. The resulting increased afterload in this hypovolemic state was without deleterious effects. Furthermore, steroids appeared to enhance the cardiac response to aortic cross-clamping.