SAN DIEGO—Separate studies by the same research team show that hyperkalemia increases the risk of death among hemodialysis (HD) patients and the frequency of hyperkalemia is greater on the day after the long interdialytic interval, according to poster presentations at Kidney Week 2015.
In a retrospective study of 36,888 HD patients with a mean age of 63 years, 3,753 (10.2%) died during follow-up, 1,604 (42.7%) from cardiovascular causes. In adjusted analyses, hyperkalemia, defined as a serum potassium level of 5.7 mEq/L or higher, was associated with a significant 10% increase in all-cause mortality. Potassium levels (in mEq/L) of 5.8 or higher, 5.9 or higher, and 6.0 or higher were associated with a significant 18%, 29%, and 37% increased risk of all-cause mortality, respectively. The study found no significant association between serum potassium level and cardiovascular death.
“Hyperkalemia appears to be associated with mortality in hemodialysis patients,” lead investigator James B. Wetmore, MD, of Hennepin County Medical Center in Minneapolis, Minn., told Renal & Urology News. “A threshold of 5.7 appears to be an important threshold at which the risk of death appears to increase significantly. Risk of death appears to steadily increase as potassium level increases.”
To compare the frequency of hyperkalemia on the day after the long and short interdialytic interval, Dr. Wetmore and his colleagues studied 4 annual cohorts of HD patients: 2007 (28,769 patients), 2008 (34,785 patients), 2009 (34,567 patients), and 2010 (36,879 patients). The prevalence of hyperkalemia events per 100 patient-months on the day after the long interdialytic interval in 2007, 2008, 2009, and 2010 was 58.7, 62.2, 62.9, and 61.6, respectively. By comparison, the prevalence of hyperkalemia events on the day after the short interdialytic interval was 28.8, 27.6, 26.3, and 26.2, respectively.
“Hyperkalemia is substantially more common on the day after the long, 72-hour interdialytic interval compared to the short, 48-hour interval,” Dr. Wetmore said. “Since hyperkalemia is likely related to death and cardiac events in hemodialysis patients, this raises the possibility that the hyperkalemia is a mechanism at least partially responsible for the increased rates of death and cardiovascular events after the long interdialytic interval.”
The researchers calculated hyperkalemia prevalence as the cumulative number of monthly episodes divided by cumulative follow-up time.