The influence of spine distraction with hypotensive condition on spinal cord. An experimental study

我们从脊髓血流和脊髓诱发电位两方面评估了临床降压麻醉常用的降压药物维持低血压对脊髓的影响，并关注脊髓自身调节。（方法）测定GOE麻醉下成年家兔的动脉压。用PGE_1和硝酸甘油诱导低血压。收缩压维持在正常血压的30%后，停止给药。血压恢复后，再次降低50%和70%，并连续测量脊髓血流量和脊髓诱发电位。另一方面，采用PGE_1进行脊柱牵张术，血压分别降低30%和50%。观察释放牵引力后脊髓血流和脊髓诱发电位的变化。采用激光多普勒法测定脊髓血流。通过l4 /5和Th9/10层间间隙插入的硬膜外电极记录了更多的上升和下降电位。刺激强度分别为3倍阈值（3T）和超最大刺激（SUPRA）。在作用机制不同的两种药物（硝酸甘油、前列腺素）维持的低血压状态下，脊髓血流量均有所减少，但与血压降低率无相关性。停药后脊髓血流量恢复较好，血压降低率较低。正如脊髓诱发电位随血压变化而变化一样，弱刺激（3T）后第二电位振幅的变化最能反映脐带血流量的变化。在脊柱牵引血压降低30%或50%后，脊髓脐带血流量进一步降低，但两种降低率之间的降低没有显著差异。脊髓牵引解除后，脊髓血流在30%复位状态下恢复，但在50%复位状态下进一步下降。减弱弱刺激后第一电位的振幅变化与减弱弱刺激后第二电位的振幅变化相似。脊髓牵张对脊髓功能的影响可以通过这些变化来评估。在临床降压麻醉中，血压一般可降低30%。在这个范围内，就脊髓血流和脊髓诱发电位评估脊髓功能而言，这种方法是安全的。少

We evaluated the effects of hypotension maintained with hypotensive drugs, generally used for clinical hypotensive anesthesia, on the spinal cord in terms of spinal cord blood flow and spinal evoked potentials, paying attention to spinal autoregulation. (Methods)The arterial pressure was monitoured in adult rabbits under GOE anesthesia. Hypotension was induced with PGE_1 and nitroglycerin. After the systoric blood pressure was maintained at 30% of the normal pressure, drug administration was discontinued. After recovery of blood pressure, the blood pressure was reduced again by 50% and 70%, and spinal cord blood flow and spi-nal evoked potentials were serialluy measured. On the other hand, spine distraction was performed with 30% and 50% reductions of blood pressure with PGE_1.Serial changes in the spinal cord blood flow and spinal evoked potentials after release of traction were evaluated. Spinal cord blood flow was measured by the laser Doppler method. As spinal evoked potentials, as … More cending ans descending potentials were recorded using extrdural electorodes inserted via the L4/5and Th9/10 interlaminar spaces. The intensities of stimulation were three times the threshold(3T) and supra-maximum stimulation(SUPRA).(Results)1.In the hypotensive state maintained with each of the 2 drugs (nitroglycerin, prostaglandin) with different action mechanisms, the spinal blood flow was decreased, but the decrease was not correlated with the reduction rate in blood pressure. The recovery of spial cord blood flow after discontinuation of each drug was better at a lower reduction rate in blood pressure.2. As changes in the spinal evoked potentials with changes in blood pressure, chabges in the amplitude of the second potential after weak stimulation(3T) best reflected those in spial cord blood flow.3. After spine traction with a 30% or 50% reduction in blood pressure, spanal cord blood flow further decreased, but the decrease did not significantly differ between the two reduction rates. After release of spinal traction, spinal cord blood flowrecoverd at the 30% reduction state but further decreased at the 50% reduction state.4. Changes in the amplitude of the first potential after descending weak stimulation were similar to those of the second potential after weak stimulation. The effects of spinal distraction on spinal cord function could be evaluated using these changes.5. In clinical hypotensive anethesia, the blood pressure is generally reduced by 30%. In this range, this method is safe in terms of spinal cord function evaluated by spinal cord blood flow and spinal evoked potentials. Less