Haghighi S S, Oro J J
Division of Neurological Surgery, University of Missouri, Columbia.
Neurosurgery. 1989 Feb;24(2):246-52. doi: 10.1227/00006123-198902000-00015.
The utility of evoked potentials in monitoring spinal cord and cerebral function in various neurosurgical and orthopedic operations has now been established. To study the effects of graded hypotension upon spinal and cortical somatosensory evoked potentials (SMEPs), and spinal motor evoked potentials (SMEPs), 12 anesthetized cats were subjected to graded hypotension ranging from a mean arterial blood pressure of 100 mmHg to 30 mmHg or less. Hypotension causes a progressive increase in onset latency and a decrease in amplitude and conduction velocity of SEPs and SMEPs. Cortical SEPs and SMEPs were sensitive to profound hypotension (MAP less than 30 mmHg). Spinal SEPs showed more resistance and disappeared at lower levels of hypotension. Immediate blood transfusion caused resumption of cortical SEPs and SMEPs within 30 minutes after infusion; however, the latency and amplitude of responses did not reach the baseline values within 1 hour after transfusion. The sequential recovery of evoked responses was dependent upon the length of hypotension. When 15 minutes elapsed between loss of responses and transfusion, cortical SEPs and SMEPs did not resume within 1 hour after infusion. No return of signals occurred if 30 minutes elapsed between the loss of evoked responses and blood reperfusion. These findings suggest that ischemia associated with profound systemic hypotension can alter or obliterate evoked responses.
诱发电位在各种神经外科和骨科手术中监测脊髓和脑功能的作用现已得到确立。为研究分级低血压对脊髓和皮层体感诱发电位（SMEP）以及脊髓运动诱发电位（SMEP）的影响，对12只麻醉猫进行分级低血压处理，平均动脉血压范围从100 mmHg降至30 mmHg或更低。低血压会导致SEP和SMEP的起始潜伏期逐渐延长，波幅和传导速度降低。皮层SEP和SMEP对深度低血压（平均动脉压低于30 mmHg）敏感。脊髓SEP表现出更强的耐受性，在较低水平的低血压时消失。立即输血可使皮层SEP和SMEP在输注后30分钟内恢复；然而，反应的潜伏期和波幅在输血后1小时内未恢复到基线值。诱发电位反应的顺序恢复取决于低血压的持续时间。当反应消失与输血之间间隔15分钟时，皮层SEP和SMEP在输注后1小时内未恢复。如果诱发电位反应消失与血液再灌注之间间隔30分钟，则信号不会恢复。这些发现表明，与深度全身性低血压相关的缺血可改变或消除诱发电位反应。
