Evaluation of Nutritional Status and Hydration in Patients on Chronic Hemodialysis by Bioelectrical Impedance Analysis
Background: Nutrition and hydration of the dialysis patients have major influences on the outcomes of chronic hemodialysis. Purpose: To characterize the states of nutrition and hydration in patients on chronic hemodialysis at Jos University Teaching Hospital (JUTH) and to evaluate the usefulness of measurements by bioelectrical impedance analysis (BIA) for these characterizations. Methods: Investigation pre-and post-hemodialysis of (A) the state of nutrition by body mass index (BMI), serum albumin and pre-albumin, and BIA-derived estimates of the fraction body fat over body weight (BF/W) and phase angle, and (B) the state of hydration by clinical examination for volume excess and BIA-derived estimates of body water (V), extracellular volume (ECFV), and the fractions ECFV/V and V over fat-free mass (V/FFM) in 10 patients on chronic hemodialysis at JUTH. Results: (A) Nutritional estimates post-dialysis: BMI 22.3±2.9 kg/m2, with 5 values in the normal range (20-25 kg/m2), 4 values < 20 kg/m2 and 1 value > 27.5 kg/m2; serum albumin 29.8±6.8 g/L, with 1 value in the normal range (35-50 g/L) and 9 values < 35 g/L; serum pre-albumin 0.26±0.12 g/L, with 6 values in the normal range (0.18-0.45 g/L) and 4 values < 0.18 g/L); BF/W 0.19±0.08, with 5 values in the normal range, 4 values indicating fat deficit and 1 value indicating fat excess; phase angle 4.4±0.8 degrees, with 5 values in the normal range (5-8 degrees) and 5 values indicating malnutrition (< 4 degrees). There was strong concordance between hypoalbuminemia, low serum pre-albumin and low values of BF/W and phase angle. Pre-and post-dialysis values agreed closely. (B) Post-dialysis estimates of hydration by BIA: V 38.6±9.8 L; ECFV 18.8±6.6 L; ECFV/V 0.48±0.06; V/FFM 0.73±0.04. The change in V during dialysis (-0.7±3.3 L) correlated highly (r = 0.99) with the corresponding change in body weight (-0.8±3.3 kg). The fractions V/FFM and ECFV/V were higher in patients with clinical evidence of volume overload than those with post-dialysis euvolemia. BIA appeared to underestimate the excess body water in a patient with ascites and pleural effusions. Conclusions: With the exception of patients with large fluid collections in body cavities, BIA provides reliable estimates of nutrition and hydration in Nigerian patients on chronic hemodialysis. Both malnutrition and overhydration are common in JUTH patients on chronic hemodialysis. These findings may assist in designing preventive and therapeutic interventions for these patients.
Keywords: Hemodialysis, nutrition, hydration, bioimpedance, Nigeria
Highland Medical Research Journal Vol. 5 (1) 2007 pp. 9-19