You see a 72 year Asian male with history of diabetes, hypertension, and ESRD on HD via a left radio-cephalic AVF while rounding in your dialysis unit. His dialysis Rx is a dialyzer D flux 250, Qb of 400ml/min, Qd- 600 ml/min for a duration of 4 hours. His Kt/V on three times a week hemodialysis has ranged between 1.6-1.8. Your dialysis unit nurse reports that most recently checked Kt/V has dropped down to 1.0 confirmed on 2 different checks. He has been compliant with his dialysis treatments and has completed the full 4 hours as prescribed. Patient feels fine. His physical exam is unremarkable with blood pressures ranging between 130-150 systolic and trace edema.
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A drop in Kt/V can be due to multiple factors. Inaccurate post dialysis BUN measurement, shortened dialysis treatment (affecting T), low access blood flow or access recirculation (the latter two affecting K), are some of the common ones. Poor access flow is the most common cause of a drop in Kt/V (40% of cases). In our patient, access flow seems maintained at 400ml/min and his treatment time has not been reduced. Access recirculation is seen in about 25% of cases of reduced Kt/V. If this is suspected, a fistulogram (Choice 3) should be done to evaluate for access stenosis. Increasing treatment time (Choice 1) and dialysate flow (Choice 2) will likely help improve Kt/V to varying degrees, however access recirculation should be ruled out first if suspected. Since the low Kt/V has already been confirmed on 2 separate occasions, monitoring and repeating in one month (Choice 4) will simply delay intervention.
Let's look at access recirculation now.