Endothelin plasma levels during heart surgery: influence on pulmonary artery pressure?

Some studies found endothelin-1 to be a trigger for pulmonary hypertension. Endothelin-1 is an endothelial derived substance with generally vasoconstrictive properties, but probably vasodilatory effects on pulmonary arteries. The aim of the present study was to look for influences of endothelin-1 plasma values on pulmonary artery pressure.

Endothelin-1 levels during and after cardiac surgery and correlations to pulmonary artery pressure were tested in 10 control patients and 21 patients with pulmonary hypertension (mean pulmonary arterial pressure > 20 mmHg, systolic pulmonary arterial pressure > 30 mmHg).

According to endothelin-1 values before anaesthesia (normal value below 4 pg/ml) patients with pulmonary hypertension could be divided into a "high endothelin-1" (10 patients, mean 8.25 +/- 2.06 pg/ml) and a "normal endothelin-1" (11 patients, mean 2.13 +/- 0.86 pg/ml) subgroup (p < 0.01). Values of the "high endothelin-1" group decreased until end of operation (from 7.58 +/- 2.35 to 2.95 +/- 1.44 pg/ml, n = 6) when pulmonary artery pressure returned to normal. Otherwise they slightly increased (from 9.43 +/- 2.24 to 11.07 +/- 1.96 pg/ml, n = 4). Levels of the "normal endothelin-1" group increased (to 2.55 pg/ml). Endothelin-1 values peaked on the intensive care unit (ICU) in all patients. Baseline endothelin-1 and systolic pulmonary artery pressure values correlated well with each other (r = 0.73, p < 0.001). Endothelin-1 decreased after extracorporeal circulation in all patients in whom pulmonary artery pressure tended to normalise, whereas no rise in pulmonary artery pressure paralleled the marked increase in endothelin-1 on the ICU. Vasodilatory effects of endothelin on pulmonary arteries can attribute to this course.

Endothelin-1 seems not to trigger pulmonary hypertension but rather to vasodilate pulmonary vasculature.