Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association
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Nephrol. Dial. Transplant. · Apr 2000
Comparative StudyA new method of post-dialysis blood urea sampling: the 'stop dialysate flow' method.
A standardized practical method of post-dialysis blood sampling is required to improve the precision of using urea kinetics in the evaluation of haemodialysis dose and to permit comparative audit. The methods recommended in the Renal Association and Dialysis Outcomes Quality Initiative (DOQI) guidelines reduce the blood pump speed to a low rate at the end of haemodialysis before blood sampling after 10 and 15 s respectively. However, these 'low flow' methods compensate only partially for cardiopulmonary recirculation and may be impractical in routine practice because they involve sequential steps and require accurate timing of sampling. Therefore we have evaluated an alternative method of stopping only the dialysate flow at the end of the haemodialysis session before performing post-dialysis blood sampling. ⋯ This study shows that there is a window period between 4 and 6 min after stopping dialysate flow at the end of the haemodialysis session when the blood urea concentration in a sample taken from any part of the extracorporeal circuit remains constantly within the co-efficient of variation of laboratory measurement, and is equivalent to a peripheral venous sample taken immediately at the end of the dialysis session. A 'stop dialysate flow' method with blood sampling after 5 min offers several advantages over 'slow flow' methods, since it allows for cardiopulmonary as well as access recirculation, does not require precise timing of blood sampling, and is simple to perform in a busy renal unit. For these reasons the 'stop dialysate flow' method may be used for routine monitoring of the adequacy of delivered haemodialysis and for comparative audit among haemodialysis centres.