Effect of hydration state on cardiac function in patients on chronic haemodialysis.

Haemodynamic studies were performed at rest and during exercise in five chronic haemodialysis patients at two different states of hydration, called "normal hydration" and "over-hydration" (mean change in body weight 2.9 kg). Apart from an increase in mean aortic pressure and cardiac index there were no signs of cardiac dysfunction at rest at normal hydration. On exercise the mean pulmonary artery and wedge pressure increased significantly while cardiac output doubled. Overhydration caused considerable increases in right and left sided heart pressures at rest, without any increase in cardiac index. These changes became more pronounced during exercise. Anaemia and arteriovenous shunting make dialysis patients very sensitive to volume load. Extreme anaemia should be avoided, and keeping dialysis patients in a state of low volume load should be given high priority.