Severe hyperkalemia requiring hospitalization: predictors of mortality

Abstract

Introduction: Severe hyperkalemia, with potassium (K+) levels ≥ 6.5 mEq/L, is a potentially life-threatening electrolyte imbalance. For prompt and effective treatment, it is important to know its risk factors, clinical manifestations, and predictors of mortality.

Methods: An observational cohort study was performed at 2 medical centers. A total of 923 consecutive Korean patients were analyzed. All were 19 years of age or older and were hospitalized with severe hyperkalemia between August 2007 and July 2010; the diagnosis of severe hyperkalemia was made either at the time of admission to the hospital or during the period of hospitalization. Demographic and baseline clinical characteristics at the time of hyperkalemia diagnosis were assessed, and clinical outcomes such as in-hospital mortality were reviewed, using the institutions' electronic medical record systems.

Results: Chronic kidney disease (CKD) was the most common underlying medical condition, and the most common precipitating factor of hyperkalemia was metabolic acidosis. Emergent admission was indicated in 68.6% of patients, 36.7% had electrocardiogram findings typical of hyperkalemia, 24.5% had multi-organ failure (MOF) at the time of hyperkalemia diagnosis, and 20.3% were diagnosed with severe hyperkalemia at the time of cardiac arrest. The in-hospital mortality rate was 30.7%; the rate was strongly correlated with the difference between serum K+ levels at admission and at their highest point, and with severe medical conditions such as malignancy, infection, and bleeding. Furthermore, a higher in-hospital mortality rate was significantly associated with the presence of cardiac arrest and/or MOF at the time of diagnosis, emergent admission, and intensive care unit treatment during hospitalization. More importantly, acute kidney injury (AKI) in patients with normal baseline renal function was a strong predictor of mortality, compared with AKI superimposed on CKD.

Conclusions: Severe hyperkalemia occurs in various medical conditions; the precipitating factors are similarly diverse. The mortality rate is especially high in patients with severe underlying disease, coexisting medical conditions, and those with normal baseline renal function.

Figure 1

Flow diagram for patient enrollment. DNR, do not resuscitate; ESRD, end-stage renal disease; RRT, renal replacement therapy.

Figure 2

Risk factors for in-hospital mortality. Malignancy, emergent admission, the presence of multi-organ failure (MOF) and/or cardiac arrest at the time of hyperkalemia diagnosis, intensive care unit (ICU) care during hospitalization, and severe clinical situations such as new-onset acute kidney injury (AKI), infection, and bleeding were strongly associated with in-hospital mortality. The mortality rate increased significantly as the difference in serum K⁺ level at admission and at its highest point (serum K⁺ ≥ 6.5 mEq/L) increased. In contrast, the mortality rate decreased in patients with drug-induced hyperkalemia, including those who used beta blockers. CI, confidence interval.