Another simpler bypassing dialysate technique for measuring post-haemodialysis BUN

Background. The most popular method for estimating post-haemodialysis BUN is the low blood flow technique. The low blood flow technique with a blood flow of 50 ml/min for 3 min may encompass the first two phases of post-haemodialysis urea rebound by access and cardiopulmonary recirculations. Some patients may have risk of clotting in extracorporeal circuit while slowing blood flow. Therefore we proposed another simpler sampling technique for measuring post-haemodialysis BUN(C 2 ). Methods. In the present study, 28 long-term haemodialysis patients were divided into two groups. In group I (n=15), C 2 sample (C 2-50 ) was collected immediately after blood flow was slowed down to 50 ml/min for another 3 min. Then blood flow was reset to 300 ml/min. Finally, C 2 sample (C 2B ) was obtained from arterial port at the end of bypassing dialysate for another 3 min. In group 2 (n=13), C 2 sample (C 2B ) was obtained from arterial port at the end of bypassing dialysate for 3 min with a blood flow of 250 ml/min. Then dialysate was reset to original flow rate and C 2 sample (C 2-50 ) was collected soon after blood flow was slowed down to 50 ml/min for another 3 min. In the meantime, recirculation rate was also checked. Results. The above two groups have similar results and there are no significant differences of post-haemodialysis BUN and calculated Kt/V between low blood flow technique and bypassing dialysate technique. Conclusion. The bypassing dialysate technique is another simpler and practical technique for the routine estimation of post-haemodialysis BUN.