Impact of hospital-acquired pneumonia on rehabilitation outcomes and mortality in patients after severe acquired brain injury: a retrospective cohort study

Background Patients after severe acquired brain injury (sABI) have an increased susceptibility to systemic infections, which can severely compromise their rehabilitation process. In this study, we aimed to evaluate the impact of hospital-acquired pneumonia (HAP) on functional outcome and mortality in a large cohort of adult patients underwent inpatient rehabilitation from post-acute to 6 months after sABI.Methods This observational retrospective cohort study included patients consecutively admitted after an acute sABI to Neurorehabilitation Unit for 6-month program between December 1, 2019, and December 31, 2022. Demographic data, etiology of sABI (traumatic vs. non-traumatic), length of stay, comorbidities, neurological impairment, presence of invasive devices (tracheostomy and nasogastric tube, percutaneous endoscopic gastrostomy), occurrence of HAP, and death during hospitalization were recorded. Functional assessments were evaluated at admission and discharge with the Functional Independence Measure (FIM), the Levels of Cognitive Functioning (LCF), and the Glasgow Outcome Scale-extended (GOS-E).Results Of the 169 patients enrolled, 78 (46.2%) developed HAP during hospitalization. Of the 169 patients enrolled, 78 (46.2%) developed HAP during hospitalization. The multivariable logistic regression analysis identified as significant risk factors for the onset of HAP during hospitalization male sex (OR 0.313, p = 0.003), severity of brain injury (OR 0.825, p = 0.011), and the presence of nasogastric tube or percutaneous endoscopic gastrostomy due to the severity of dysphagia (OR 14.336, p = 0.024). The occurrence of HAP was the main predictor of poorer recovery at discharge in terms of FIM (p = 0.003) and LCF (p = 0.009), independent of other confounding variables at admission (e.g., age, severity, and etiology of brain injury). Furthermore, the occurrence of HAP was independently associated with a threefold (OR 3.088; p = 0.020) increase in mortality during inpatient rehabilitation.Conclusion Severity of brain injury, male sex and presence of nasogastric tube or percutaneous endoscopic gastrostomy due to the severity of dysphagia may represent an early indicator of the risk of HAP in patients with sABI. Implementing preventive strategies and application of the care bundle to reduce the incidence of HAP, including improved oral hygiene, early mobilization, and appropriate management of dysphagia, may not only improve functional outcomes but also reduce mortality in patients undergoing rehabilitation after sABI.