Ventilator-Associated Pneumonia and Aromatic Microbial Metabolites in Patients After Ischemic and Hemorrhagic Stroke

Background and Aims

Stroke patients, particularly those requiring mechanical ventilation, are at high risk of developing ventilator-associated pneumonia (VAP), which is strongly linked to increased in-hospital mortality. This study aimed to evaluate whether aromatic microbial metabolites, along with stroke type, sex, and age, are associated with the development of VAP and in-hospital mortality.

Methods

This retrospective observational study included 29 adult patients with acute stroke (9 men, 20 women; median age 77 years, range 31–88). Patients were stratified by stroke type: ischemic (n=23) and hemorrhagic (n=6). Serial serum samples (median sampling interval 4 days, IQR 3–7) were analyzed by gas chromatography-mass spectrometry for phenyllactic acid, p-hydroxyphenyllactic acid, p-hydroxyphenylacetic acid, and their sum (Sum 3). The peak Sum 3 value was used as the exposure variable. VAP was defined according to CDC criteria as a new radiographic infiltrate in patients receiving mechanical ventilation for ≥48 hours. Groups were compared using the Mann–Whitney U test and Fisher’s exact test.

Results

VAP was associated with 100% in-hospital mortality (7/7) versus 14% (3/22) in patients without VAP (p=0.0001). Peak Sum 3 levels were significantly higher in patients with VAP (median 8.6 [IQR 4.6–15.0] vs 2.8 [IQR 1.6–5.5] µM; p=0.006) and in non-survivors (median 6.8 [IQR 4.8–11.9] vs 2.5 [IQR 1.6–3.7] µM; p=0.001). However, Sum 3 levels did not differ between ischemic and hemorrhagic stroke subtypes (median 3.9 vs. 3.0 µM; p=0.96). Hemorrhagic stroke showed non-significant trends toward higher rates of mechanical ventilation (67% vs. 39%), VAP (50% vs. 17%), and in-hospital mortality (50% vs. 30%). Sex and age were not significantly associated with VAP or in-hospital mortality.

Conclusions

Aromatic metabolite profiling may serve as a useful complement to clinical criteria for the early identification of stroke patients at highest risk of poor outcome. This hypothesis warrants validation in larger prospective cohorts.