Seminars in thoracic and cardiovascular surgery
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Semin. Thorac. Cardiovasc. Surg. · Jan 1998
ReviewMonitoring of somatosensory evoked potentials: a primer on the intraoperative detection of spinal cord ischemia during aortic reconstructive surgery.
The acute interruption of blood supply to the spinal cord during thoracic and thoracoabdominal aortic reconstructions, if unabated, inevitably causes neurological injury secondary to regional hypoxia. Techniques that address the multifactorial nature of spinal cord ischemic injury have evolved to preserve neuromotor function. However, the overall incongruity of the spinal cord's vascular anatomy makes it virtually impossible to predict, with any degree of certainty, the duration of aortic cross-clamping (AXC) that can safely be endured. ⋯ Sudden loss of signal as witnessed in a Type III SSEP implies compromised critical intercostal vessels and indicates their expeditious reimplantation. A gradual (30 to 50 minutes) SSEP "fadeout" corresponds to marginal distal perfusion, suggesting the presence of extensive pathology. Intraoperative evoked potential monitoring, in conjunction with distal aortic perfusion, permits rapid identification and correction of compromised spinal cord blood flow, permitting repair of aortic lesions without the added liability of time constraints.
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Semin. Thorac. Cardiovasc. Surg. · Jan 1998
Control of proximal hypertension during aortic cross-clamping: its effect on cerebrospinal fluid dynamics and spinal cord perfusion pressure.
Postoperative paraplegia remains the most devastating complication of surgery of the descending and thoraco-abdominal aorta. Control of the proximal hypertension that follows cross-clamping of the thoracic aorta to repain aneurysms of the descending and thoraco-abdominal aorta is necessary to prevent left ventricular failure, myocardial infarction, and hemorrhagic cerebral events. Both pharmacological and mechanical modalities used to control central hypertension during aortic occlusion affect cerebrospinal fluid dynamics and spinal cord perfusion pressure. ⋯ This approach can maintain mesenteric and spinal cord blood flow, therefore preventing the multiple organ dysfunction syndrome caused by release of cytokines from the splanchnic district and decreasing the incidence of postoperative paraplegia from spinal cord ischemia. In cases of limited retroperfusion, partial exsanguination and cerebrospinal fluid drainage can be used in conjunction with left atrial-femoral artery bypass to prevent rises in cerebrospinal fluid pressure and maintain spinal cord blood flow above the threshold necessary to prevent neurological injury. The use of oxygenated perfluorocarbons in the subarachnoid space to provide passive oxygenation of the spinal cord during aortic occlusion remains experimental and requires further investigation.