What technical factors should be considered when measuring the dose of dialysis?
The method by which the predialysis and postdialysis blood samples are obtained is important in ensuring accurate results.
Blood urea nitrogen (BUN) levels are subject to rebound of three different types: access recirculation, cardiopulmonary recirculation, and remote compartment rebound.
By following a specific technique for blood drawing, the effect of access recirculation on the postdialysis BUN sample is minimized. Both the predialysis and postdialysis samples should be drawn during the same dialysis session.
The postdialysis BUN samples should be obtained using either the slow flow or stop flow technique. With the slow flow technique, the dialysate flow is turned off and the blood pump is slowed to about 100 mL/min for about 15 seconds prior to obtaining the sample from the sampling port.
Alternatively, with the stop flow technique, after the aforementioned procedures are performed, the blood pump is stopped and the arterial and venous blood lines are clamped prior to obtaining the sample.
