Understanding definitive and probable stroke-associated pneumonia: Risk factors and clinical outcomes

The aim of this study was to identify the risk factors for stroke-associated pneumonia (SAP), to investigate its impact on functional outcomes at discharge, and to examine the effect of white blood cell (WBC) count, C-reactive protein (CRP), and lymphocyte count on the development of SAP.

This retrospective study included patients age ≥ 18 years, those presenting within the first 7 days of an acute ischemic and/or hemorrhagic stroke, having either first-time or recurrent incident between September 2018 and June 2019. The diagnosis of stroke was made based on clinical findings as evidenced by cranial computed tomography (CT) or magnetic resonance imaging (MRI). The classification of stroke was based on the International Classification of Diseases (ICD)-10. The Bamford Classification was used to identify ischemic stroke subtypes. The WBC and CRP levels were recorded at the time of admission and 24 h after admission. The clinical severity of the stroke was measured by the National Institutes of Health stroke scale (NIHSS) on the admission day. Functional outcome measures were the NIHSS and Modified Rankin Scale scores (mRS) at discharge.

A total of 481 patients who met the inclusion criteria were recruited. Of these, 82 (18.2 %) were diagnosed with pneumonia. While 78 patients had SAP, four were accepted as hospitalization-associated pneumonia (HAP). Fifty-two (11 %) patients were d-SAP. Overall, SAP and HAP occurred in 82 patients with a median latency from admission of 3.7 days. Definitive SAP developed in a median duration of 3 days, while p-SAP developed in a median duration of 4 days. Sputum cultures were performed in 123 patients, and most of the cultures were negative (75.6 %). The positive results contained Staphylococcus aureus, Proteus mirabilis, Haemophilus influenzae (5.7 %, 3.3 %, 2.4 %, respectively). The median NIHSS value was 16 (range, 3-23) in the d-SAP and 9.5 in p-SAP group (p < 0.001). The patients with d-SAP had poorer outcomes at the time of discharge, indicating a statistically significant difference (p < 0.001).

Our study results showed that d-SAP group had higher incidence of stroke severity, atrial fibrillation, lower ejection fraction value, and increased WBC level at the time of admission and follow-up. Poor functional outcome was highly related with definitive SAP. Lymphopenia was associated with pneumonia frequency, lesion size, and poor functional outcome.