Importance of Volume Control
The influence of volume control on clinical outcomes cannot be overemphasized. Hypervolemia is intimately associated with arterial hypertension, heart failure, atherosclerosis and malnutrition. The increased relative risk associated with high transporter status among PD patients (see Prognostic Value of Transport Status) is probably explained by the resultant poor ultrafiltration and consequent hypervolemia.
A prospective, two year APD study was performed in anuric patients in thirteen European countries to determine the factors that affect patient and technique survival1. The dialysis prescription was altered throughout the study to achieve a weekly creatinine clearance target > 60 l/week/1.73 m2 and UF > 750 ml/day. The main independent predictors of patient survival were age, the presence of more than two comorbidities and severe malnutrition. Increased UF at baseline was significantly associated with improved patient survival (p = 0.0048). Although not statistically significant, higher UF during the study follow-up continued to be associated with better survival. It is of interest that the poor prognosis generally associated with CAPD patients with high membrane transport did not apply to patients undergoing APD. Perhaps the ability of APD to improve UF with the use of short and frequent dwells neutralizes the higher risk associated with higher solute transport and reduced UF.
Asci et al. in a prospective single-center study over 24 months reported that control of hypertension was possible when extracellular fluid volume was kept under control using hypertonic PD solutions and salt restriction among long-term PD patients2. Sustained normovolemia was associated with a low incidence and regression of left ventricular hypertrophy (LVH).
The importance of adequate ultrafiltration is also exemplified by the association between volume and nutrition in PD patients. Malnutrition is a known strong predictor of mortality. Cheng et al. have recently shown a strong association between fluid status and nutritional status in PD patients. Improved fluid status was associated with improvement in nutritional status, whereas deterioration in fluid status was associated with development of malnutrition3.
Brown E, Davies SJ, Rutherford P, Meeus F, Borras M, Riegel M, Divino Filho JC, Vonesh E, Van Bree M on behalf of the EAPOS Group. Survival of functionally anuric patients on automated peritoneal dialysis: The European APD outcome study. J Am Soc Nephrol 14:2948-2957, 2003
Asci G, Ozkahya M, Duman S, Toz H, Erten S, Ok E. Volume control associated with better cardiac function in long-term peritoneal dialysis patients. Perit Dial Int 26:85-88, 2006
Cheng LT, Tang W, Wang T. Strong association between volume status and nutritional status in peritoneal dialysis patients. Am J Kidney Dis 45:891-902, 2005