Mechanisms of spinal cord injury after cross-clamping of the descending thoracic aorta.

Cross-clamping of the descending thoracic aorta for surgical correction of coarctation carries a risk of injury to the spinal cord, which is usually attributed to insufficient blood supply along the spinal arteries. To detect inadvertent interruption of spinal cord perfusion, lumbar pressure was monitored during operation on the aorta in eight patients. One patient incurred ischemic damage of the spinal cord, resulting in paraparesis. In this patient, spinal fluid pressure increased to such high levels that it may have caused tamponade of the cord. The pressure increase resulted from expansion of cerebral vessels caused by an acute rise of arterial pressure after clamping, probably aggravated by the administration of a vasodilating drug. During operations in which the circulation of the spinal cord is compromised long enough to cause ischemic damage, the femoral artery and spinal fluid pressures should be monitored. If the pressure difference between femoral artery and lumbar cavity drops to a dangerously low level, a shunting procedure should be performed.