Effects of Nitroglycerin on Central Haemodynamics and VA/Q Distribution Early after Coronary Bypass Surgery

Publisher Website
Google Scholar
Abstract
Central hemodynamics and ventilation-perfusion (.ovrhdot.VA/.ovrhdot.Q) distributions were studied in 9 patients, 21 h after coronary bypass surgery, before and during nitroglycerin (TNG) infusion. .ovrhdot.VA/.ovrhdot.Q distributions were established with the multiple inert-gas elimination technique of Wagner and West. Administration of TNG resulted in a decrease in mean arterial pressure, a slight reduction in cardiac output, stroke volume and a significant increase in heart rate, possibly explained by an initial relative hypovolemia. Pulmonary arterial pressures and filling pressures for the right and left ventricles decreased significantly. There was a significant reduction in PaO2 [arterial partial pressure of O2] and an increase in venous admixture (.ovrhdot.QVA/.ovrhdot.QT) from 11.3 to 16.5% of cardiac output. This was mainly due to an initial SF6-shunt of 6.4% increasing to 12.8%. Only 3.5% of cardiac output during TNG was due to perfusion of hypoventilated areas. The mean for the control .ovrhdot.Q-distribution was 0.88 with a mean log SD of .+-. 1.14, indicating .ovrhdot.VA/.ovrhdot.Q-mismatch, and did not change significantly. The reduction of pressures in the pulmonary vascular bed was accompanied by increased ventilation of areas with high .ovrhdot.VA/.ovrhdot.Q.