EFFECT OF NITROGLYCERIN ON SPINAL-CORD ISCHEMIA AFTER THORACIC AORTICCROSS-CLAMPING

Background. Thoracic aortic cross-clamping with the use of sodium nitr oprusside (SNP) has been shown to cause a decrease in spinal cord perf usion pressure and an increased incidence of paraplegia. Nitroglycerin is frequently used in this setting. This study investigated the effec ts of nitroglycerin and SNP on spinal cord ischemia. Methods. Three gr oups of 8 mongrel dogs underwent thoracic aortic cross-clamping for 45 minutes. Proximal pressure was maintained between 95 and 100 mm Hg wi th SNP, nitroglycerin, or phlebotomy. All animals were neurologically evaluated 24 hours later by a blinded observer, and the findings were confirmed by histopathologic study. Statistical analysis (p value of l ess than 0.05) of measured hemodynamic data was by analysis of varianc e and of Tarlov scores, the Mann-Whitney U test. Results. Distal aorti c pressures (p < 0.001), Tarlov scores, and spinal cord perfusion pres sures (p < 0.01 and p < 0.05 for SNP group and nitroglycerin group, re spectively) were significantly higher in the phlebotomy group compared with the SNP and NTG groups. Cerebrospinal fluid pressures were signi ficantly lower in the phlebotomy group compared with the SNF group (p < 0.001). Conclusions. The use of either NTG or SNP was associated wit h a high incidence of paraplegia. Nitroglycerin appears to be no safer than SNP when used during thoracic aortic cross-clamping.