THE EFFECT OF ARTERIOVENOUS-FISTULAS IN HEMODIALYSIS-PATIENTS ON WHOLE-BODY AND SEGMENTAL BIOELECTRICAL-IMPEDANCE

Background. Bioelectrical impedance (BIA) is a potentially useful meth od for measuring body water and soft-tissue composition in patients wi th chronic renal failure. The majority of whole body impedance is deri ved from the limbs with only a small contribution from the trunk, and thus abnormalities of the limbs could have an exaggerated effect on es timates of total body impedance. Methods. This study investigated the effect of arteriovenous fistulae in the arm in haemodialysis patients on body composition measurement by whole body BIA. Body composition es timates from measurements on fistula and non-fistula sides of the body were compared and segmental impedance measurements of the arms were a lso performed. Results. Whole body resistance was markedly lower on th e fistula side of the body compared with the non-fistula side at 517.1 (124.3) Omega compared with 561.5 (121.2) Omega, P < 0.0005. This dif ference was accounted for by differences in the arm segments. This was attributed to swelling of the fistula arm which had a greater mid-arm circumference at 28.5 (2.1) cm compared with the contralateral side a t 27.5 (2.0) cm, P < 0.05. This resulted in greater estimates for tota l body water from the fistula side at 38.6 (10.0) kg compared with 36. 6 (8.6) kg from the non-fistula side, P < 0.05 and fat-free mass at 51 .1 (11.8) kg from the fistula side compared with 49.1 (11.2) kg from t he non-fistula side, P < 0.005. Estimates of body fat from the fistula side, 13.1 (6.9) kg, were less than the non-fistula side, 15.0 (6.0), P < 0.005. Conclusions. The presence of arteriovenous fistulae for va scular access in haemodialysis patients may have a significant effect on estimates of body composition by BIA.