Incidence and determinants of hyperkalemia and hypokalemia in a large healthcare system

Background Hypo- and hyperkalemia in clinical settings are insufficiently characterized and large-scale data from Europe lacking. We studied incidence and determinants of these abnormalities in a large Swedish healthcare system. Methods Observational study from the Stockholm CREAtinine Measurements project, including adult individuals from Stockholm accessing healthcare in 2009 (n = 364,955). Over 3-years, we estimated the incidence of hypokalemia, defined as potassium < 3.5 mmol/L, hyperkalemia, defined as potassium > 5 mmol/L, and moderate/severe hyperkalemia, defined as potassium > 5.5 mmol/L. Kidney function was assessed by estimated glomerular filtration rate (eGFR). Results Of 364,955 participants, 69.4% had 1–2 potassium tests, 16.7% had 3–4 tests and the remaining 13.9% had > 4 potassium tests/year. Hypokalemia occurred in 49,662 (13.6%) individuals, with 33% recurrence. Hyperkalemia occurred in 25,461 (7%) individuals, with 35.7% recurrence. Moderate/severe hyperkalemia occurred in 9059 (2.5%) with 28% recurrence. The frequency of potassium testing was an important determinant of dyskalemia risk. The incidence proportion of hyperkalemia was higher in the presence of diabetes, lower eGFR, myocardial infarction, heart failure (HF), or use of renin angiotensin-aldosterone system inhibitors (RAASi). In adjusted analyses, women and use of loop/thiazide diuretics were associated with lower hyperkalemia risk. Older age, lower eGFR, diabetes, HF and use of RAASi were associated with higher hyperkalemia risk. On the other hand, women, younger age, higher eGFR and baseline use of diuretics were associated with higher hypokalemia risk. Conclusion Hypo- and hyperkalemia are common in healthcare. Optimal RAASi and diuretics use and careful potassium monitoring in the presence of certain comorbidities, especially lower eGFR, is advocated.