Total solute extraction versus clearance in the evaluation of standard and short hemodialysis

The authors compared the efficiency of standard HD (t = 240 minutes, Qb = 300 ml/min, Qd = 500 ml/min) with short HD (t = 150 minutes, Qb = 500 ml/min, Qd = 700 ml/min). The study was carried out in 11 patients in two sequential dialysis sessions, utilizing the same high surface area hollow fiber dialyzers, after a 2 day interdialytic period. With short HD, as expected, the clearance (Cl) of BUN, creatinine (Cr), and phosphates (P) was significantly higher than in standard HD:Cl BUN = 331 vs. 225, Cl Cr = 286 vs. 193, and Cl P = 231 vs. 176 ml/min. No significant difference in the total BUN extraction (measured on the total amount of exhausted dialysate) was found between the two techniques. As to Cr and P, despite higher Cl in short HD, the total extractions were significantly lower. In conclusion, in the evaluation of short HD efficiency, instantaneous Cl can be adequate for small molecules, while for larger solutes, other parameters, such as total extraction, must be considered.