TEMPORARY OR sustained hypotension associated with circulatory collapse is not uncommon after release of the cross clamped abdominal aorta. The abrupt pressure drop attending restoration of aortic flow is a form of normovolemic shock attributed to sequestration of a segment of the circulating volume in dilated peripheral vessels.5Attempts have been made to counteract declamping hypotension by rapid venous transfusion, peripheral infusion of vasopressors,5 9 arterial bypass during occlusion,3 pneumatic compression of the extremities,2 and neutralization of accumulated acid metabolites distal to the cross clamp.' None of these methods have been completely successful in preventing the consequences of vascular redistribution accompanying aortic release. the temporary occlusion would prevent the undesirable hemodynamic changes that occur under these circumstances.
Methods and MaterialsMongrel dogs weighing between 12 and 24 Kg. were anesthetized with intravenous pentobarbital, intubated and ventilated with a mechanical respirator. A branch of the right femoral artery and the right common carotid artery were cannulated and connected to strain gauge transducers for measuring peripheral and central arterial pressures respectively. Through a midline laparotomy the abdominal aorta was isolated above or below the renal arteries, without ligating any major vessels, and circumscribed with umbilical tape tourniquets. A left thoracotomy was carried out through the fifth intercostal space and the pericardium incised. The left circumflex coronary artery and ascending aorta were isolated and surrounded by calibrated noncannulating flow probes of a square wave electromagnetic flowmeter. Flow and pressure measurements were read directly on a multi-channel physiologic recorder. Multiple determinations were made before, during, and after cross clamping the abdominal aorta below (IR) and above (SR) the renal arteries. In selected experiments femoral artery flow and circumflex coronary artery pressures were also determined.Heparinized arterial transfusions of homologous or autologous blood in weighed Fenwal bags were rapidly administered 414
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