Effects of prenalterol on central haemodynamics and VA/Q distribution early after open-heart surgery.

The effects of intravenous injection of prenalterol, a selective beta 1-adrenoceptor agonist, on central haemodynamics and the distribution of ventilation-perfusion (VA/Q) were assessed in eight patients after aortic and/or mitral valve replacement. VA/Q distributions were determined by the multiple inert gas elimination technique. Administration of prenalterol resulted in a significant increase in cardiac output and heart rate with no changes in mean pulmonary arterial pressure and wedge pressure. There was an insignificant fall in arterial oxygen tension from 14.3 to 12.4 kPa, accompanied by a significant increase in the inert gas shunt from 6.4 to 11.3% of cardiac output, while the configuration of the distribution of perfusion and ventilation on VA/Q remained unchanged. The increase in shunt was probably more an effect of the increase in cardiac output than a direct effect of the drug on the pulmonary vascular bed.