Risk calculation for hyperkalemia in heart failure patients

Abstract

Introduction: Since it was propagated to use aldosterone inhibition (Aldo i) on top of ACE inhibitors (ACEi) for the treatment of heart failure, the incidence of hospitalization and death because of hyperkalemia has risen. We aimed to develop a model to estimate the risk of hyperkalemia in patients treated for heart failure in a tertiary reference hospital and to identify precipitating factors.Methods: 125 CHF patients were studied retrospectively between January 2002 and April 2006. Thirty of these patients developed episodes of hyperkalemia (K ≥ 5.5 mmol/l). Both groups were compared for possible risk factors for hyperkalemia (age, GFR, NYHA class, diabetes mellitus, ejection fraction and medication use (ACEi, angiotensin receptor blockers, Aldo i)). Moreover it was assessed whether a precipitating factor for the hyperkalemic episode could be identified.Results: On multivariate logistic regression analysis DM (OR 2.9; 95% CI=1.05–8.3 p=0.041), GFR < 45 ml/min (OR 4.1; 95% CI=1.6–10.5 p=0.004) and NYHA class III–IV (OR 2.4; 95% CI=0.9–6.3 p=0.086) were independently associated with hyperkalemia, whereas age, ejection fraction and medication sort and dose, were not. Based on these ORs a model was designed which could predict hyperkalemia with a sensitivity of 90% and a specificity of 47%. 38% of episodes of hyperkalemia were precipitated by periods of dehydration (diarrhoea, fever) or change of medication, whereas in 62% no precipitating factor could be identified. In all but one hyperkalemic episode there was concomitant transient loss of renal function (i.e rise of creatinin of at least 25%).Conclusion: We identified kidney function, diabetes mellitus and heart failure class as independent risk factors of hyperkalemia. The model based on these risk factors gives only a modest prediction of hyperkalemia. Moreover, the majority of the hyperkalemic episodes develop without precipitating factor, although the concomitant transient loss of renal function suggest there is unnoticed transient dehydration in these subjects. These findings imply that heart failure patients in a third line reference hospital should be very closely monitored to minimize the risk for hyperkalemia.