Volume status and blood pressure in continuous ambulatory peritoneal dialysis patients

The pathophysiology of hypertension in dialysis patients is largely attributed to positive sodium balance and volume expansion. Whereas the relationship between fluid status and blood pressure control in hemodialysis patients is well established, this relationship is not well studied in peritoneal dialysis patients.

Methods: 100 stable CAPD patients who had been dialyzed for more than 3 months, as well as 60 healthy controls, were studied cross-sectionally. CAPD patients were divided into three groups according to their blood pressure level: group 1 (normotension), group 2 (controlled hypertension with antihypertensive medication (AHM)) and group 3 (uncontrolled hypertension with AHM). Extracellular water (ECW) and intracellular water (ICW) were measured using bioimpedance spectroscopy in all subjects. Dialysis adequacy and transport test was conducted in each patient.

Results: Height normalized ICW (nICW) was much lower, and ECW/ICW was higher in both male and female dialysis patients as compared to healthy controls. nECW was also significantly higher in group 3 when compared to group 1. The dose of AHM was similar in group 2 and group 3. In female CAPD patients, there were no differences in urinary volume (UV) and the total fluid removal among the three patient groups. However, in male CAPD patients, UV and total fluid removal were significantly higher in group 3 than in group 1. Renal and total removal of sodium was also significantly higher in group 3 male patients than group 1.

Conclusions: Peritoneal dialysis patients with uncontrolled hypertension are more volume overloaded and their blood pressure may be difficult to control by AHM alone. These findings indicate that volume control preferably by dietary salt and fluid restriction should be intensified in hypertensive CAPD patients.