A haemodynamic study of hypotension during haemodialysis using electrical bioimpedance cardiography

Continuous recording of beat-to-beat changes in haemodynamic parameters such as arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance, was done in 52 uraemic patients. The study was performed during the haemodialysis session, using a system combining a personal computer, an arterial pressure recorder, and an electrical bioimpedance cardiography monitor. Forty-six episodes of dialysis-induced hypotension occurred in 26 patients. Systolic arterial pressure and total peripheral resistance decreased by -39.3 +/- 2% and -36.3 +/- 4% respectively during acute hypotension; in contrast, there was an increase in cardiac output (+13.9 +/- 6.7%), while heart rate and stroke volume did not change significantly. It was possible to distinguish two types of collapse on the basis of heart rate behaviour: the classic 'tachycardiac' collapse with heart rate increase and stroke volume decrease, and the so-called 'bradycardiac' collapse with a paradoxical reduction in heart rate and an increase in stroke volume. 'Bradycardiac' collapses were observed in 54% of the cases. The administration of atropine in one patient resulted in an immediate increase in heart rate. The development of bradycardia and hypotension during haemodialysis seems to be related to a sudden parasympathetic vagal overactivity and could be attributed to the Bezold-Jarish reflex.