Does Renal Function Predict Short- and Medium-Term Mortality and Hospital Readmissions in Poststroke Patients?

See related article, p 2896 Renal impairment commonly occurs in the elderly and alongside various cardiovascular risk factors. Additionally, renal impairment in itself is often an adverse prognostic factor in many common cardiovascular disorders, such as stroke. Risk stratification to recognize high-risk patients with poor outcomes is an important aspect of overall clinical management and may allow aggressive targeted interventions in a subset of these patients. Equally, it may identify those in whom a holistic approach with focus on quality of life is more appropriate. Thus, many risk stratification models have included renal function as a variable, with varying success. The most commonly used biomarker to estimate renal function, creatinine, is cheap and universally available. However, it lacks the sensitivity offered by newer biomarkers and is influenced by various factors such as muscle mass. Impaired renal function among stroke survivors has been linked with poor short-term outcomes. Nevertheless, this is unsurprising as renal dysfunction often coexists with multiple comorbidities that act as risk factors for developing the condition or develop as a result of it, such as hypertension, diabetes mellitus, previous myocardial infarction, and atrial fibrillation. In general, renal dysfunction may be considered a surrogate for poor general health. However, an important consideration when using renal function as a variable in any predictive risk model is the fact that there is no specific treatment for the condition and overall management is focused rather on coexisting comorbidities. A significant number of medications are also renally excreted. They include secondary prevention medications used to treat stroke survivors such as antiplatelet and anticoagulation therapies. A reduction in renal function can, therefore, be detrimental as it causes excessive levels of medication in the body, leading to toxic side effects. In addition, some of these medications may lack efficacy when used in patients with severe renal dysfunction. In the current issue of Stroke, El Husseini et al report shortand medium-term mortality and hospital readmissions stratified by admission renal function in a nationwide cohort of 204 652 Medicare beneficiaries aged ≥65 years after an acute ischemic stroke. The majority of patients (51.2%) had estimated glomerular filtration rate <60 mL/min per 1.73 m with a minority having estimated glomerular filtration rate <15 mL/min per 1.73 m (without dialysis, 0.6%, and on dialysis, 2.8%). Multivariable Cox proportional hazards models demonstrated an independent association of renal dysfunction with increased 30-day and 1-year mortality and hospital readmissions. Unsurprisingly, the highest 30-day and 1-year mortality were seen in those with estimated glomerular filtration rate <15 mL/min per 1.73 m without dialysis (hazard ratio, 2.09; 95% CI, 1.66–2.63) and among patients on dialysis (hazard ratio, 2.65; 95% CI, 2.49–2.81), respectively. Patients on dialysis had the highest 30-day and 1-year hospital readmissions (hazard ratio, 2.10; 95% CI, 1.95–2.26; hazard ratio, 2.55; 95% CI, 2.44–2.66, respectively). Nevertheless, some limitations are worth highlighting. The use of a single creatinine measurement taken on admission to determine renal function may not be an accurate reflection of true baseline levels. Indeed, many of these patients would subsequently be started on medications that can affect their renal function. Furthermore, as a consequence of the stroke, some patients may suffer from difficulty in swallowing, compromising their nutritional status, and increasing their risk of developing renal dysfunction during their hospital stay. Alternative, potentially more accurate methods may, therefore, be to use their discharge creatinine levels or an average of all measured levels, to calculate the estimated glomerular filtration rate. Also, risk is a dynamic process, and prediction based on a one-off admission assessment of a particular risk factor or biomarker may be flawed since patients may have accumulated incident comorbidities during the study period which would not have been taken into account. In addition, length of index hospitalization, treatment received by patients during their hospital stay, and frailty assessment scores should also be considered as these are important factors that can significantly influence outcomes in terms of mortality and hospital readmissions. From the study by El Husseini et al, in spite of increased comorbidities among patients with worsening renal function, they were equally (if not less likely) to be discharged on antiplatelet therapy and less likely to be discharged on cholesterolreducing therapy. Also, these patients were often discharged to another healthcare facility rather than home. A systematic review (16 studies) found that length of index hospitalization and discharge location/need for nursing care were the most common predictors for stroke severity. The need for nursing care is often another measure for poor functional status. However, objective The opinions expressed in this article are not necessarily those of the editors or of the American Heart Association. From the Liverpool Centre for Cardiovascular Science, University of Liverpool, United Kingdom (W.Y.D., G.Y.H.L.); Liverpool Heart and Chest Hospital, United Kingdom (W.Y.D., G.Y.H.L.); and Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Aalborg University, Denmark (G.Y.H.L.). Guest Editor for this article was Markku Kaste, MD, PhD. Correspondence to Gregory Y.H. Lip, MD, Liverpool Centre for Cardiovascular Science, University of Liverpool, William Henry Duncan Bldg, 6 W Derby St, Liverpool, L7 8TX. Email gregory.lip@ liverpool.ac. uk Does Renal Function Predict Shortand Medium-Term Mortality and Hospital Readmissions in Poststroke Patients?