30-Day Risk-Standardized Mortality and Readmission Rates After Ischemic Stroke in Critical Access Hospitals

Abstract

The critical access hospital (CAH) designation was established to provide rural residents with local access to emergency and inpatient care. CAHs, however, have poorer short-term outcomes for pneumonia, heart failure, and myocardial infarction compared with other hospitals. We assessed whether 30-day risk-standardized mortality rates (RSMRs) and risk-standardized readmission rates (RSRRs) after ischemic stroke differ between CAHs and non-CAHs. The study included all fee-for-service Medicare beneficiaries 65 years of age or older with a primary discharge diagnosis of ischemic stroke (International Classification of Diseases, 9th revision codes 433, 434, 436) in 2006. Hierarchical generalized linear models calculated hospital-level RSMRs and RSRRs, adjusting for patient demographics, medical history, and comorbid conditions. Non-CAHs were categorized by hospital volume quartiles and the RSMR and RSRR posterior probabilities in comparison with CAHs were determined using linear regression with Markov chain Monte Carlo simulation. There were 10 267 ischemic stroke discharges from 1165 CAHs and 300 114 discharges from 3381 non-CAHs. The RSMRs of CAHs were higher than non-CAHs (11.9%± 1.4% vs 10.9%± 1.7%; P<0.001), but the RSRRs were comparable (13.7%± 0.6% vs 13.7%± 1.4%; P=0.3). The RSMRs for the 2 higher volume quartiles of non-CAHs were lower than CAHs (posterior probability of RSMRs higher than CAHs=0.007 for quartile 3; P<0.001 for quartile 4), but there were no differences for lower volume hospitals; RSRRs did not vary by annual hospital volume. CAHs had higher RSMRs compared with non-CAHs, but readmission rates were similar. The observed differences may be partly explained by patient characteristics and annual hospital volume.