The use of near infrared interactance in hemodialysis

Forty‐one consecutive admissions to a hemodialysis center were evaluated. Demographic information including age, gender, race, and diagnosis was collected. Patients, >18 years old, with end stage renal disease and on hemodialysis for at least one year were included. Those with edema or known ascites were excluded. Weight was measured before and after hemodialysis (HD) using a standard scale and by considering the amount of fluid loss by the hemodialysis machine. Body composition including total body water (TBW) was calculated before and after HD using near infrared interactance (NIR). All measurements were completed during half hour before and after HD. Forty‐one patients included: men (n = 26), women (n = 15); median age 58 (range 28–88 years). Twenty‐eight were African American and the rest Caucasians. The amount of intravascular fluid taken after HD (assessed by weight reduction) ranged 0–5 L with median 2.2 L. NIR analysis for the same patients at the same time showed different total body water measurements in 91% of cases (P > 0.05). Moreover, NIR analysis showed increase in total body water in 24% of patients even though the hemodialysis machine showed a loss of total body water; median of 1.3 (range: 0–3L). The error in measuring body composition with NIR was both large and varied (random and not systematic error). We conclude that NIR analysis cannot be considered as a reliable method to evaluate body composition, especially total body water, amongst patients with end stage renal disease undergoing hemodialysis.