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.
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There is growing awareness of a need not only to identify patients with chronic renal failure (CRF) at an earlier stage in the disease process, but also to initiate treatment strategies earlier, in order to delay both progression of CRF and co-morbid diseases and to define the optimal time required to prepare CRF patients for renal replacement therapy (RRT). These three strategies are linked, and rely on appropriate identification of patients at risk of renal disease. The challenge currently facing nephrologists is both how to minimize the consequences of late referral and how to improve the timeliness of referral. ⋯ There is ample evidence that strategies to delay progression of renal disease are effective, as are strategies to reduce cardiovascular disease. Anaemia and a fall in haemoglobin concentration have been associated with left ventricular hypertrophy and with growth of the left ventricle. A combined approach is necessary for best nephrological clinical practice, with a clear definition of early renal insufficiency; this will involve the development of tools to permit early identification of patients with early renal insufficiency, and the implementation of strategies to optimize treatments aimed at both delaying progression and preparing patients for RRT.