Preservation of spinal cord function and prevention of paralysis during aortic occlusion via veno-arterial bypass.
Academic Article
Overview
abstract
Paraplegia secondary to spinal cord ischemia is a too frequent devastating complication of thoracic aneurysm surgery. We examined the ability of veno-arterial bypass (VAB) to ensure adequate spinal cord blood flow during aortic cross-clamping by monitoring spinal cord function via somatosensory evoked potentials (SEP's) and postoperative motor function. Dogs were placed on VAB using a heparin-bonded roller pump circuit without systemic heparinization. SEP latency and amplitude were monitored continuously. The respirator FIO2 was set at 100% while the aorta was cross-clamped for one hour with the bypass adjusted to keep distal arterial pressure at greater than 60 mmHg. After one hour the aorta was unclamped, bypass discontinued, and the animals recovered. SEP's were always present during VAB as long as the distal pressure was kept at greater than 60 mmHg. There were several transient hypotensive episodes (less than 5 min) which were accompanied by reversible loss of SEP's. None of the animals displayed any gait abnormalities post-op. These findings using this simple bypass technique suggest the following conclusions: (1) SEP's degenerate (increased latency and decreased amplitude) in response to hypoxia; (2) spinal cord function can be maintained for up to one hour during hypoxic conditions; (3) SEP's can be used to monitor sensory spinal cord function under these conditions; and (4) heparinless VAB can provide spinal cord protection while also allowing monitoring of SEP's to ensure adequate spinal cord perfusion.
