Purpose: Hypo- and hyperkalemia are associated with an increased mortality risk. Serum potassium (K+) levels associated with these risks and relationships to comorbidity, however, are not well defined. We evaluated the odds of death in patients with and without comorbid conditions, stratified by K+ level.
Methods: De-identified medical records (2007-2012) from a large US population aged ≥5 years with 2 or more K+ readings were evaluated. Patients aged 45-64 years with comorbidities of CKD stages 3-5, heart failure, diabetes, hypertension, and cardiovascular disease (n = 231,070) were identified by ICD-9 codes and biochemical data, excluding those with acute kidney injury or end stage renal disease, and compared with controls without these conditions (n = 146,645). A separate analysis of patients aged ≥65 years was conducted. Index K+ value was defined as the last reported value prior to a pre-determined cut-off date. Mortality was evaluated through hospital discharge records and Social Security registry information.
Results: Patients with cardiorenal comorbidities aged 45-64 years and index K+ levels <4.1 mEq/L and >4.6 mEq/L had a significant increase in mortality (Figure). This finding was also observed in patients aged ≥65 years. The general pattern remained after adjustments for demographic characteristics (sex, race) and comorbidities associated with the propensity to develop hypo- and hyperkalemia.
Conclusions: Our results confirm that patients with hypo- or hyperkalemia are at greater risk for mortality than those with normal K+, and that mortality risk is significantly higher in patients with cardiorenal comorbidities and is independent of demographic characteristics. The increased mortality in patients with comorbidities occurs even at K+ levels within the usual normal laboratory range.