Effects of Sodium Nitroprusside and Nitroglycerin on the Arterial Blood Oxygenation during Cross - Clamping of Descending Aorta in Dogs

Shim, Jae Yong

Abstract

Sodium nitroprusside(SNP) and nitroglycerin(NTG) have been used as one of the adjuvants that can modify the hemodynamie changes during cross-clamping of thoraco-abdominal aortic surgery. Cardiovascular changes after cross-clamping of aorta were well studied, but the respiratory effects of cross-clamping of aorta were not well defined. And both vasodilators are known to increase the intrapulmonary shunt when administered during anesthesia. So we have evaluated the effects on the arterial oxygenation of combination therapy of SNP and NTG over single use of SNP during cross-clamping of aorta in 12 dogs which anesthetized by halothane. After completion of anesthesia and preparation for cross-clamping of aorta was done at 10 cm distal to left subclavian artery through thoracotomy at 6th intercostal space. In control group, no drug was administered. In SNP group(2.5ug/kg/min) and SNP+NTG group(8 pg/kg/min), the drugs were administered before and after cross-clamping of descending thoracic aorta in each group for 45 minutes. The hemodynamic parameters were measured before aortic eross-clamping and at 1, 15, 30, 45 minutes after aortic cross-clamping. Results were follows, 1) Arterial oxygen tensions were decreased significantly only at 45 minutes after cross-clamping of aorta in SNP+NTG group(P<0.05) and no significant difference between SNP group and SNP+NTG group. 2) Intrapulmonary shunt was increased significantly at l5 minutes after cross clamping in SNP+NTG group(P<0.05), but not significant difference between NTG group and SNP+NTG group. 3) PCWP was significantly decreased at 15, 30, 45 minutes after cross-clamping in SNP and SNP+NTG group compared to control group(P<0.05), but not significant difference between SNP group and SNP+NTG group. 4) PVR were decreased significantly at 15, 30 minutes after cross-clamping of aorta in SNP+ NTG group compared to control group(P<0.05). But there was no significant diffrence between SNP group and SNP+ NTG group. 5) CI were increased at 45 minutes after aortic cross-clamping in SNP group and at 15, 30, 45 minutes after aortic cross-clamping in SNP+NTG groupg<0.05). But there was no significant difference between SNP and SNP+NTG group. These results showed that sodium nitroprusside did not affect the arterial oxygenation during cross-clamping of thoracic aorta and combination use of sodium nitroprusside and nitroglycerin had no additional risk of increasing arterial hypoxemia.