Sieving coefficient inaccuracies during hemodiafiltration in patients with hyperbilirubinemia

Hemodiafiltration has assumed an important role in the supportive therapy of critically ill patients. The viability of the filter used for hemodiafiltration can be monitored by estimating the sieving coefficient of small molecules such as creatinine and/or urea. We report on three patients with severe hyperbilirubinemia whose creatinine sieving coefficient was spuriously elevated as a result of discordance in the accuracy of creatinine measurement in plasma and ultrafiltrate respectively. This discordance was a consequence of lack of bilirubin clearance during hemodiafiltration. As a result, while the plasma creatinine determination by the kinetic Jaffe method was negatively influenced by the hyperbilirubinemia, the ultrafiltrate creatinine was not. This report is the first to document the lack of bilirubin clearance during hemodiafiltration and its impact on the calculation of sieving coefficient based on creatinine. The use of urea as the solute for determining the sieving coefficient allows for an accurate estimate and provides a valid means of monitoring this parameter in the setting of hyperbilirubinemia.