Key PointsRenin-angiotensin-aldosterone system inhibitor (RAASi) therapy is frequently downtitrated or discontinued after a hyperkalemia episode.Reducing RAASi therapy after a hyperkalemia episode is associated with increased risk of hospitalization compared with maintaining RAASi.Our data suggest that a hospitalization within 6 months could be avoided if 25 patients maintained instead of reduced their RAASi therapy.BackgroundRenin-angiotensin-aldosterone system inhibitor (RAASi) therapy provides cardiorenal protection but is often downtitrated or discontinued after a hyperkalemia episode. This observational study describes the extent of hyperkalemia-related RAASi reduction in patients with CKD and/or heart failure (HF) and estimates the number needed to treat (NNT) to avoid a first hospitalization if RAASi had been maintained at the prior dose.MethodsHealth care registers and claims data from Germany, Spain, Sweden, and the United Kingdom were used to identify nondialysis patients with CKD and/or HF who had a hyperkalemia episode while on RAASi. Patients whose RAASi therapy was reduced (downtitrated/discontinued) after the hyperkalemia episode were propensity score matched to those with maintained RAASi, and their risks of a hospitalization within 6 months were estimated using the Kaplan-Meier method. On the basis of the absolute difference in this 6-month risk, the NNT framework was applied to estimate the number of patients who needed to have maintained instead of reduced their RAASi to avoid a first hospitalization during this period.ResultsOverall, 40,059 patients from Germany, Spain, Sweden, and the United Kingdom were included. Presence of CKD at baseline was similar across countries (72%-92%), while HF was less common in Spain (18%) versus other countries (32%-71%). After the hyperkalemia episode, RAASi was reduced in 25%-57% of patients. After propensity score matching, the 6-month risk of hospitalization was consistently higher in those with reduced versus maintained RAASi; the absolute risk difference ranged from 2.7% to 7.3%. Applying the NNT framework, these data suggest that a first hospitalization within 6 months could potentially have been avoided if 25 patients had maintained instead of reduced their RAASi.ConclusionsOur findings suggest a potential for avoiding a first hospitalization, even within a short time frame, by increasing adherence to guidelines to maintain instead of reduce RAASi after a hyperkalemia episode.