Pulmonary Extraction of 5-Hydroxytryptamine and Norepinephrine before and after Cardiopulmonary Bypass in Man
Pulmonary extraction of 14C-5-hydroxytryptamine and 3H-norepinephrine was estimated in patients undergoing aortocoronary saphenous vein grafting. Identical mixtures of both amines were administered intravenously before Cardiopulmonary bypass and again just after bypass. Immediately after each injection, 6 ml of blood was withdrawn into tubing, at a constant rate, simultaneously from both the pulmonary artery and the left atrium. Each set of tubing was then divided into six segments, and the 3H and 14C content of each segment was measured. In this manner, total isotope collected and blood isotope concentration as a function of time at the two sampling sites were compared directly. Before bypass in every patient studied, less 5-hydroxytryptamine and norepinephrine were withdrawn on the left than on the right of the lungs, implying pulmonary extraction of both amines. In nine patients, the mean percent extraction was 65 ± 4% for 5-hydroxytryptamine and 23 ± 5% for norepinephrine (P < 0.005). After bypass, the percent extraction of both norepinephrine and 5-hydroxytryptamine was increased in all but one patient; values for norepinephrine were increased to a realtively greater extent. These data represent a direct demonstration of 5-hydroxytryptamine and norepinephrine extraction by human lungs and also suggest that total Cardiopulmonary bypass may alter the process.
- Received December 22, 1971.
- Accepted April 18, 1972.
- © 1972 American Heart Association, Inc.