Inpatient hospitalisation and mortality rate trends from 2004 to 2014 in the USA: a propensity score-matched case–control study of hyperkalaemia

Abstract

ObjectiveTo study the trends of hyperkalaemia in USA inpatient hospitalisation records with heart failure (HF), chronic kidney disease (CKD), acute kidney injury (AKI) and/or type II diabetes mellitus (T2DM) from 2004 to 2014 with respect to prevalence and inpatient mortality.DesignObservational cross-sectional and propensity score-matched case–control study.SettingThe National Inpatient Sample (representing up to 97% of inpatient hospital discharge records in the USA) from 2004 to 2014Participants120 513 483 (±2 312 391) adult inpatient hospitalisation records with HF, CKD/end-stage renal disease (ESRD), AKI and/or T2DM.ExposureHyperkalaemia, defined as the presence of an International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code of ‘276.7’ in any of the first 15 diagnostic codes.Primary and secondary outcome measuresThe outcomes of interest are the annual rates of hyperkalaemia prevalence and inpatient mortality.ResultsAmong 120 513 483 (±2 312 391) adult inpatient hospitalisations with HF, CKD/ESRD, AKI and/or T2DM, we found a 28.9% relative increase of hyperkalaemia prevalence from 4.94% in 2004 to 6.37% in 2014 (p<0.001). Hyperkalaemia was associated with an average of 4 percentage points higher rate of inpatient mortality (1.71 post-matching, p<0.0001). Inpatient mortality rates decreased from 11.49%±0.17% to 6.43%±0.08% and 9.67%±0.13% to 5.05%±0.07% for matched cases with and without hyperkalaemia, respectively (p<0.001).ConclusionsHyperkalaemia prevalence increased over time and was associated with greater inpatient mortality, even after accounting for presentation characteristics. We detected a decreasing trend in inpatient mortality risk, regardless of hyperkalaemia presence.