ABSTRACT
PURPOSE: We examined the changes in evoked spinal cord potentials (ESCP) during profound hypothermic circulatory arrest to estimate the safe ischemic time. METHODS: We monitored ESCPs during surgery for descending thoracic or thoracoabdominal aneurysms in five patients. Evoked spinal cord potential recordings were obtained before cooling (baseline), then every few minutes during circulatory arrest, and at the end of the operation. RESULTS: After circulatory arrest, the amplitude of ESCPs decreased with time. We calculated the simple linear regression between the amplitude of ESCPs and the circulatory arrest time by the least-squares method, and found a highly linear relationship between amplitude and arrest time in all five patients. The time until disappearance of ESCPs was estimated as 50.7 +/- 20.4 min (95% level of confidence). CONCLUSION: When an ESCP disappeared, ischemic spinal cord injury had occurred. This demonstrates the potential value of estimating the time of disappearance of ESCPs to prevent ischemic spinal cord injury during descending thoracic aortic surgery.
