Clamping the thoracic or thoraco-abdominal aorta causes rapid and important physiologic changes that can result in major complications in several organ systems. The clamp-induced increase in cardiac afterload raises mean arterial pressure, causing shifts in blood volume and increasing myocardial oxygen demand, which can lead to left ventricular decompensation and failure. Cross-clamping can also contribute to pulmonary complications, although the mechanisms for this effect are complex and not fully understood. Visceral ischemia and reperfusion injury are significant adverse effects of aortic cross-clamping, both in and of themselves, and because visceral ischemia can promote systemic coagulopathy. Shunting and left heart bypass can be used to minimize the duration of visceral ischemia, and serial abdominal examinations and blood gas monitoring should be used postoperatively to detect any visceral ischemic injury. Postoperative renal dysfunction and failure, sometimes necessitating temporary or lifelong hemodialysis, can result from the significant loss of renal blood flow during cross-clamping. Adequate hydration, optimizing circulating blood volume, and providing distal aortic or renal perfusion can help to prevent renal injury. Paraplegia and paraparesis can result from clamping-induced spinal cord ischemia. Cerebrospinal fluid drainage and other methods of maintaining spinal perfusion pressure can help to prevent these complications, both intraoperatively and postoperatively.
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