The Effect of Fluid Overload on Clinical Outcome in Southern Chinese Patients Undergoing Continuous Ambulatory Peritoneal Dialysis

Abstract

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Background: Fluid overload is frequently present in dialysis patients and one of the important predictors of patient outcome. This study aimed to investigate the influence of fluid overload on all-cause mortality and technique failure in Southern Chinese continuous ambulatory peritoneal dialysis (CAPD) patients. ♦

Methods: This was a post hoc study from a cross-sectional survey originally designed to investigate the prevalence and associated risk factors of fluid overload defined by bioimpedance analysis (BIA) in CAPD patients from January 1, 2008, to December 31, 2009. All 307 CAPD patients completing the original study were followed up until December 31, 2012. ♦

Results: With a median follow-up period of 38.4 (19.2 - 47.9) months, 52 patients died. Patients with fluid overload (defined by extracellular water/total body water [ECW/TBW] ≥ 0.40) had a significantly higher peritonitis rate (0.016 vs 0.011 events/month exposure, p = 0.018) and cerebrovascular event rate (3.9 vs 1.1 events/100 patient years, p = 0.024) than the normal hydrated patients. Moreover, the results showed a significant rising of all-cause mortality (log-rank test = 5.59, p = 0.018), and a trend of increasing cardiovascular disease (CVD) mortality (log-rank test = 2.90, p = 0.089) and technique failure (log-rank test = 3.78, p = 0.052) in the patients with fluid overload. Fluid overload independently predicted all-cause mortality (hazard ratio [HR] = 12.98, 95%, confidence interval [CI] = 1.06 - 168.23, p = 0.042) and technique failure (HR = 13.56, 95% CI = 2.53 - 78.69, p = 0.007) in CAPD patients after adjustment for confounders. ♦

Conclusions: Fluid overload defined by BIA was an independent predictor for all-cause mortality and technique failure in CAPD patients. Continuous ambulatory peritoneal dialysis patients with fluid overload had a higher peritonitis rate, cardiovascular event rate, and poorer clinical outcome than those patients with normal hydration.

Keywords: Fluid overload; bioimpedance analysis; mortality; nutrition; outcome; peritoneal dialysis; technique failure.

Figure 1 —

ROC analysis of ECW/TBW (AUC=0.64, cut-off 0.40, sensitivity 0.61, specificity 0.60, p=0.002), ICW (AUC=0.46, p=0.42), ECW (AUC=0.49, p=0.84), and ECW/height (AUC=0.51, p=0.79) for all-cause mortality. ROC = receiver-operating characteristic curve; ECW = extracellular water; TBW = total body water; AUC = area under the curve; ICW = intracellular water.

Figure 2A —

Change of urine volume (mL/24 hours) in the 307 CAPD patients with fluid overload (ECW/TBW≥0.4, n=205) and normal hydration (ECW/TBW<0.4, n=102) followed for a median of 38.4 months (-160 [-500–0] vs -70 [-450–0] mL/24 hours, p=0.36). CAPD = continuous ambulatory peritoneal dialysis; ECW = extracellular water; TBW = total body water.

Figure 2B —

Change of residual renal function (mL/min/1.73 m²) in the 307 CAPD patients with fluid overload (ECW/TBW≥0.4, n=205) and normal hydration (ECW/TBW<0.4, n=102) followed for a median of 38.4 months (-1.50 [-3.0 to -0.31] vs -1.07 [-3.01 to -0.24] mL/min/1.73 m², p=0.35). CAPD = continuous ambulatory peritoneal dialysis; ECW = extracellular water; TBW = total body water.

Figure 3 —

Kaplan-Meier survival curves for the patients with ECW/TBW above or below the ROC-derived cut-off for all-cause mortality (A), CVD mortality (B), technique failure (C) in the 307 CAPD patients followed for a median of 38.4 months. ECW = extracellular water; TBW = total body water; CVD = cardiovascular disease; ROC = receiver-operating characteristic curve; CAPD = continuous ambulatory peritoneal dialysis.