CAN BIOELECTRICAL-IMPEDANCE BE USED TO MEASURE TOTAL-BODY WATER IN DIALYSIS PATIENTS

The measurement of total body water (TBW) by bio-electrical impedance (BEI) in a group of renal patients was evaluated against the tritium d ilution method. The effect of haemodialysis and the presence of perito neal dialysate on the impedance were also investigated. The correlatio n between the two methods was r = 0.9, with the standard deviation of the differences being 3.66 1 (raw typically 40 l). The BEI method over estimated the actual weight loss after haemodialysis, but underestimat ed the volume of peritoneal dialysate in situ. The BEI method would no t be appropriate for use in assessing total body water and monitoring acute volume changes in patients with renal failure who are on strict fluid restriction.