Effects of chronic beta-blockade on compensatory mechanisms during acute isovolaemic haemodilution in patients with coronary artery disease.

Abstract

We have compared compensatory mechanisms during acute isovolaemic haemodilution of 12 ml/kg body weight of blood with hydroxyethyl starch (450,000/0.7) exchange, in non-beta-blocked and beta-blocked patients with coronary artery disease. During haemodilution, mean concentrations of haemoglobin decreased from 12.8 (SEM 0.2) to 10.1 (0.1) g dl-1 (P < 0.01). Only beta-blocked patients had an increase in cardiac index (P < 0.01); in non-beta-blocked patients, cardiac index remained constant. In both groups oxygen extraction increased (P < 0.01), but the increase tended to be greater in non-beta-blocked patients (P = 0.06). Oxygen consumption was maintained in both groups. There were no ECG signs of myocardial ischaemia. We conclude that beta-blocked and non-beta-blocked patients with coronary artery disease tolerated well moderate haemodilution to a haemoglobin value of approximately 10 g dl-1, however, compensatory haemodynamic mechanisms differed fundamentally between the two groups.