Validity of internal filtration-enhanced hemodialysis as a new hemodiafiltration therapy

In order to improve solute removal efficiency, several types of dialyzers with enhanced internal filtration (IF) were introduced for clinical applications. In these dialyzers, enhanced IF increased convective transport of the solute in addition to diffusive transport. Internal filtration-enhanced hemodialysis (IFEHD) defined as hemodialysis therapy using the enhanced IF dialyzer seems to be more convenient in comparison with conventional hemodiafiltration therapies because of no additional equipments such as a roller pump. In this paper, the validity of IFEHD was examined during several types of experimental studies. As a result, the experimental study with several types of enhanced IF dialyzers indicated values of relative solute clearance in an aqueous solution that were higher than unity compared to the conventional dialyzer. The K values obtained for myoglobin as a larger molecule were more than twice as high. The value of IF flow rate (Q(IF)) was evaluated by pulsed Doppler ultrasonography. The blood flow velocity at a cross-sectional plane of the dialyzer was directly measured along the dialyzer during a bovine in vitro study using a newly developed probe slider. Doppler ultrasonography is a useful method as a bedside monitoring of the Q(IF) value in a dialyzer because it is noninvasive for the patient. Time course of the Q(IF) value was examined for 6 h during a bovine in vitro study. The Q(IF) decreased within 45 min after the start of the experiment and reached constant values after that. Although creatinine and beta(2)-microglobulin K values remained constant with time during the experiment, alpha(1)-microglobulin K values gradually and albumin K value steeply decreased with time. This is because these solutes transfer through the membrane strongly affected by fouling. The validity of IFEHD was clarified during the experimental studies. Development of a dialyzer with enhanced IF, however, should take account of the patient's safety. Contaminations such as endotoxin invasion from the dialysate to the patient should be avoided.