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

ABSTRACT

Background

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.

Methods

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.

Results

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.

Conclusions

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.