Clinical factors associated with hyperkalemia in patients with congestive heart failure.

BACKGROUND: Patients with congestive heart failure (CHF) are at risk for hyperkalemia because of coexisting comorbidities and use of multiple medications that impair potassium (K) excretion such as angiotensin converting enzyme (ACE) inhibitors.

OBJECTIVE: To identify clinical factors associated with hyperkalemia on initial presentation in patients hospitalized for CHF.

DESIGN: A case-control study.

SETTING: Two university-affiliated tertiary-care hospitals.

SUBJECTS: Using ICD-9 code for CHF, CHF admissions with hyperkalemia on presentation (cases) were identified from a population of 938 non-dialysis-dependent CHF patients. CHF admissions with normokalemia on presentation were used as controls. Hyperkalemia was defined as serum K > or = 5.6 mmol/L, and normokalemia as serum K > or = 3.5 and < or =5.5.

METHODS: Data were collected on demographic characteristics, clinical variables, comorbidity and medication use. Factors associated with hyperkalemia on initial presentation were examined.

RESULTS: Mean age did not differ between cases [76 years, standard deviation (SD) = 12] and controls (75 years, SD = 12) (P = 0.824). Mean potassium levels for cases and controls were 6.2 mmol/L (range 5.6 to 8.2) and 4.3 mmol/L respectively (P < 0.001). On multivariate analysis, diabetes mellitus [odds ratio (OR) = 2.42, 95% confidence interval (CI) = 1.04-5.59], creatinine clearance <40 mL/min (OR = 8.36, CI = 2.73-25.56), use of spironolactone (OR = 4.18, CI = 1.27-13.79), and use of ACE inhibitors (OR = 2.55, CI = 1.06-6.13) were independently associated with hyperkalemia.

CONCLUSIONS: In CHF patients, hyperkalemia on presentation is independently associated with diabetes, creatinine clearance <40 mL/min, use of spironolactone, and use of ACE inhibitors. Recommendations for use of spironolactone and ACE inhibitors in CHF, and the intensity of serum K monitoring need to be clarified to account for patients at higher risk for hyperkalemia.