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

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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