Predicting the risk of hyperkalemia in patients with chronic kidney disease starting lisinopril

Abstract

Purpose Angiotensin‐converting enzyme (ACE) inhibitors are recommended for patients with chronic kidney disease (CKD) because they slow disease progression. But physicians' concerns about the risk of hyperkalemia (elevated serum potassium level), a potentially fatal adverse effect, may limit optimal management with ACE‐inhibitors. We synthesized known predictors of hyperkalemia into a prognostic risk score to predict the risk of hyperkalemia. Methods We assembled a retrospective cohort of adult patients with possible CKD (at least one estimated glomerular filtration rate (eGFR) value less than 60 ml/min/1.73 m²) who started an ACE‐inhibitor (i.e., incident users) between 1998 and 2006 at a health maintenance organization. We followed patients for hyperkalemia: (1) potassium value >5.5 mmol/L; or (2) diagnosis code for hyperkalemia. Cox regression synthesized a priori predictors recorded in the electronic medical record into a risk score. Results We followed 5171 patients and 145 experienced hyperkalemia, a 90‐day risk of 2.8%. Predictors included: age, eGFR, diabetes, heart failure, potassium supplements, potassium‐sparing diuretics, and a high dose for the ACE‐inhibitor (lisinopril). The risk score separated high‐risk patients (top quintile, observed risk of 6.9%) from low‐risk patients (bottom quintile, observed risk of 0.7%). Predicted and observed risks agreed within 1% for each quintile. The risk increased gradually in relation to declining eGFR with no apparent threshold for contraindicating ACE‐inhibitors. Conclusions The risk score separated high‐risk patients (who may need more intensive laboratory monitoring) from low‐risk patients. The risk score should be validated in other populations before it is ready for use in clinical practice. Copyright © 2010 John Wiley & Sons, Ltd.