PROSTACYCLIN AND THROMBOXANE LEVELS IN PLEURAL SPACE FLUID DURING CARDIOPULMONARY BYPASS

Prostaglandins exhibit a variety of cardiovascular actions that may af fect the hemodynamic recovery of the ischemic myocardium after cardiop ulmonary bypass. We have observed a decrease in the mean arterial pres sure on autotransfusion of the accumulated pleural cavity fluid during operation. One aim of this study was to determine the concentrations of prostacyclin and thromboxane A(2) in the pleural cavity fluid by me asuring their stable metabolites, 6-keto-PGF(1 alpha) and thromboxane B-2, respectively, in 8 consecutive patients undergoing myocardial rev ascularization, and to compare them with the arterial levels. A second aim was to quantify the hemodynamic effect of the pleural cavity flui d during operation. The concentration of 6-keto-PGF(1 alpha) in the pl eural cavity fluid was significantly higher than the arterial concentr ation (mean, 21.6 +/- 18.2 ng/mL; p < 0.01), The concentration of thro mboxane B, was also raised compared with the arterial concentration (m ean, 3.62 +/- 5.96 ng/mL; p < 0.2). The percentage fall in the mean ar terial pressure was 29.7% +/- 8.86% (p < 0.02), which was transient an d lasted 1 to 3.5 minutes. The hemoglobin concentration, potassium lev el, and pH were also measured. This study shows that the pleural cavit y fluid during cardiac operations contains significant amounts of endo genous prostacyclin. Considering the potential benefit of prostacyclin on the recovering myocardium, we believe that this fluid should be tr ansfused as a volume replacement, keeping in mind the transient phase of hemodynamic instability.