Changes in body composition following haemodialysis as assessed by bioimpedance spectroscopy.

BACKGROUND/OBJECTIVES: Patients with chronic kidney disease treated by haemodialysis (HD) are at increased risk of sarcopenia. Bioelectrical impedance spectroscopy (BIS) can be used to determine body composition, and is one of the several potential screening tools for sarcopenia. The newer generation of portable hand-held devices can be readily used in dialysis centres. The results from BIS devices using a two-compartmental model of body composition can be affected by hydration status and so ideally measurements should be made when patients are not overhydrated. More recently BIS devices using a three-compartmental body model, which separate normally hydrated lean tissues from extracellular water (ECW) excess. We wished to determine whether body composition measured using such a BIS device was affected by hydration status.

SUBJECTS/METHODS: We performed BISs pre and post HD using a three-body compartmental model.

RESULTS

BISs were recorded in 48 patients; 68.8% male; mean age 67.70±14.21 years, weight pre dialysis 70.54±18.07, which fell post to 68.58±17.78 kg, ECW fell 16.92±4.76 vs 15.66±4.43 l, P<0.001, whereas there was no change for intracellular water 14.84±4.27 vs 14.90±4.68 l. Fat-free mass index (FFMI) fell 17.87±3.98 vs 16.78±3.97 kg/m, P<0.001, whereas fat mass index (FMI) increased from 7.87±3.98 vs 8.12±3.81 kg/m, P=0.002. A fall in FFMI was associated with an increase in FMI (r=0.804, P<0.001).

CONCLUSION

FMI and FFMI measured by bioelectrical impedance assessment are both confounded by hydration status. Although pre-dialysis measurements are more convenient, we suggest BIS should preferably be performed post-dialysis when patients are less overhydrated and have less electrolyte imbalances.