Depressed pulmonary removal of [3H]prostaglandin E1 after prolonged cardiopulmonary bypass

Pulmonary removal of [3H]prostaglandin E1 ([3H]PGE1) was measured by double indicator-dilution techniques after bolus injections of indocyanine green and trace amounts of [3H]PGE1 before and after 1-3 h of total cardiopulmonary bypass (CPB) or 3 h of left-heart bypass (LHB) in 18 anesthetized dogs. Before bypass, pulmonary removal was 85.7 +/- 1.2% (means +/- SE, n = 18) and was unchanged on restoration of normal circulation after 1-2 h of CPB (80.6 +/- 1.8%, n = 7) or 3 h of LHB (87.4 +/- 1.6%, n = 4). However, on restoration of normal pulmonary arterial blood flow after 3 h of CPB, removal was significantly decreased to 74.5 +/- 2.2% (P less than 0.01, n = 7). Postbypass depression of [3H]PGE1 removal may explain our previous observations that intrabypass elevations in endogenous immunoreactive prostaglandin E in dogs were not entirely reversible on cessation of 3-4 h of CPB. Possible factors underlying depression of post-CPB pulmonary removal of [3H]PGE1 include: 1) local saturation of [3H]PGE1 removal secondary to intrapulmonary or intravascular release of prostaglandin E, 2) inhibition of prostaglandin dehydrogenase activity, or 3) damage to endothelial cell transport of [3H]PGE1 from the pulmonary microcirculation.