Interdialytic weight gain as a marker of blood pressure, nutrition, and survival in hemodialysis patients.

BACKGROUND Excessive interdialytic weight gain (IDWG) is usually related to an overload of sodium and water, and is the most important factor for arterial hypertension in dialysis. On the other hand, food intake also contributes to IDWG, and is the basic factor for nutrition. The objective of this study is to assess the long-term prognostic effect of IDWG and its relationship with the nutritional status and blood pressure in patients in hemodialysis (HD). METHODS We describe the results of a 5-year prospective observation study in which 134 HD patients were included (70 males and 64 females), with ages between 18 and 81. Initially, the average data were collected during 4 weeks, including total IDWG and percentages according to dry weight (IDWG%), nutritional parameters, and blood pressure. Patients were divided into 3 cohorts according to IDWG% (<2.9, 2.9-3.9, and >3.9%, respectively). Student t test, ANOVA, linear regression analysis, and Kaplan-Meier survival curves compared with log-rank test were used as statistical tools. RESULTS The mean IDWG% for the whole studied population was 3.5 +/- 1.1% (1.5-8.0%). It was not related to gender, but had an inverse correlation with age (P < 0.000) and serum bicarbonate level (P= 0.009). It was directly correlated with predialysis systolic and diastolic blood pressure, nPCR, urea and creatinine levels (P < 0.01 for all of them), and the body mass index (P < 0.000). Serum levels of albumin (44.7 +/- 4.0 g/dL) and prealbumin (31.9 +/- 7.4 mg/dL) had a direct correlation with total IDWG (P < 0.01). We found no significant relationship between or IDWG% and ferritin and transferrin levels. Five-year actuarial survival was 0.38, 0.52, and 0.63, respectively, in the 3 cohorts for IDWG% (P < 0.01). CONCLUSION Our results show that a greater IDWG is directly associated with a better nutritional status, although it is also associated with higher predialysis blood pressure. The greater the IDWG%, the better the long-term prognosis of the patients. The beneficial effects of IDWG on the nutritional status and prognosis are greater than the negative aspects that depend on its effects on blood pressure. One must distinguish clearly between some isolated instances of not complying with a diet from those situations where a higher IDWG is merely a reflection of a good nutritional status, and one must be careful so that dietary recommendations will not have a negative influence on nutritional aspects. One must watch and correct the trend towards higher acidosis in patients with a greater IDWG.