| Abstract: | The plasma concentration of 6-keto-PGF1 alpha, the stable degradation product of prostacyclin, was similar in the radial and pulmonary arteries and in the coronary sinus before and after the induction of the anesthesia in patients undergoing coronary artery bypass surgery. After the beginning of the mechanical ventilation and anesthesia the pulmonary vascular resistance decreased although no changes were detected in the plasma levels of 6-keto-PGF1 alpha or TXB2. During the prebypass period after the sternotomy and cannulation of the large vessels the plasma level of 6-keto-PGF1 alpha was increased similarly in the radial and pulmonary arteries and even more in the coronary sinus. During the cardiopulmonary bypass the concentration of 6-keto-PGF1 alpha remained at the increased level as compared to the values before the anesthesia. This indicates that pulmonary circulation is perhaps not the main source of prostacyclin in man. The plasma level of TXB2 was increased during the prebypass period significantly only in the coronary sinus, but during the bypass also in the radial artery. The concentration ratio of 6-keto-PGF1 alpha/TXB2 was increased significantly during the prebypass period in the radial and pulmonary arteries. At the same time the pulmonary vascular resistance was, however, returned to the preanesthesia level and was thus not decreased. The vascular resistance in the systemic circulation was increased during the prebypass period. The plasma level of 6-keto-PGF1 alpha or TXB2 in the radial and pulmonary arteries did not correlate significantly with the total vascular resistance in the systemic and pulmonary circulation, respectively. The vascular resistance in the coronary circulation did not correlate significantly with TXB2 level in the radial artery or coronary sinus. There was, however, a slight positive correlation between the blood flow and the concentration of TXB2 in the coronary sinus (r = 0.76, P less than 0.01). Coronary sinus flow did, however, not correlate with the plasma level of 6-keto-PGF1 alpha in the radial artery or coronary sinus. These results indicate that the detected plasma concentrations of prostacyclin and thromboxane A2 have no significant effects on the total vascular resistance in vivo. |
