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Nephrol Dial Transplant. 2018 Jul 1;33(7):1207-1214. doi: 10.1093/ndt/gfx241.

Serum-to-dialysate potassium gradient and its association with short-term outcomes in hemodialysis patients.

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Healthcare Analytics and Insights, DaVita Clinical Research, Minneapolis, MN, USA.
Relypsa Inc, Redwood City, CA, USA.
Department of Clinical Pharmacy, University of California San Francisco, San Francisco, CA, USA.
Selzman Institute for Kidney Health, Section of Nephrology, Department of Medicine, Baylor College of Medicine, Houston, TX, USA.
Division of Nephrology, Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA.



A high serum-to-dialysate potassium (K+) gradient at the start of dialysis leads to rapid lowering of serum K+ and may confer a greater risk of adverse events. Here, we examined the near-term association of K+ gradient with clinical outcomes.


This retrospective (2010-11) event-based study considered 830 741 patient-intervals, each defined by a pre-dialysis measurement of serum K+ made among adult Medicare Parts A and B enrollees who received in-center hemodialysis on a Monday/Wednesday/Friday schedule at a large US dialysis organization. K+ gradient was considered based on the difference in K+ concentration (serum-dialysate) on the date of measurement; analyses accounted for multiple observations per patient. Outcomes considered were: all-cause and cardiovascular hospital admissions, emergency department (ED) visits and deaths.


Higher K+ gradient was associated with younger age, greater fistula use, lower comorbidity scores and better nutritional indices. Adjusting for patient differences, there was a dose-response relationship between higher K+ gradient and greater risks of all-cause hospitalization and ED visit. A similar trend was seen for cardiovascular hospitalization but did not achieve statistical significance. No associations were observed with mortality, potentially due to a low number of events.


Higher K+ gradient is independently associated with greater risk of all-cause hospitalizations and ED visits. Further research is needed to determine whether interventions that reduce the K+ gradient ameliorate this risk.

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