Effect of metagenomic next-generation sequencing on clinical outcomes in adults with severe pneumonia post-cardiac surgery: a single-center retrospective study

Reports on the application of metagenomic next-generation sequencing (mNGS) in adult patients with severe pneumonia after cardiac surgery remain limited. This study aimed to evaluate the clinical outcomes of mNGS analysis of bronchoalveolar lavage fluid (BALF) in such patients.A retrospective cohort study was conducted on adult patients with severe pneumonia after cardiac surgery. Samples were collected from patients in the surgical intensive care unit (SICU) of Sichuan Provincial People's Hospital between January 2019 and March 2024. Upon diagnosis of severe pneumonia, bronchoalveolar lavage fluid was obtained via bronchoscopy within 24 h. The mNGS group was composed of patients tested using mNGS and conventional microbiological tests. BALF was detected only by the conventional microbiological test (CMT) method in the CMT group, which involved examining bacterial and fungal smears and cultures at least. We reviewed a total of 4,064 cardiac surgeries, and based on the inclusion criteria, a total of 113 adult patients with severe pneumonia after cardiac surgery were included in this study. The overall positive rate detected by mNGS was significantly higher than that of the culture method (98% vs. 58%, P<0.0001). After receipt of the microbiological results, the mNGS group exhibited a higher incidence of antibiotic adjustments in comparison to the CMT group (P = 0.0021). After adjusting the treatment plan based on microbial testing results, the mNGS group showed an improvement in ventilator-free days within 28 days (P = 0.0475), with a shorter duration of invasive ventilation compared to the CMT group (P = 0.0208). The detection of mNGS can significantly improve the Acute Physiology and Chronic Health Evaluation-II (APACHE II) score (P = 0.0161) and Sequential Organ Failure Assessment (SOFA) score (P = 0.0076) on the 7th day after admission to the SICU. In this study, the mNGS group showed signs of having a positive impact on the length of stay in ICU (median: 9 days, IQR: 7-10 days vs. median: 10 days, IQR: 8-13.75 days, P = 0.0538), length of stay in Hospital (median: 20 days, IQR: 17-28 days vs. median: 25 days, IQR: 18-29 days, P = 0.1558), mortality in 28 days (19% vs. 20%, P = 0.8794), in-hospital mortality (19% vs. 22%, P = 0.7123); however, statistical analysis did not confirm these differences to be significant. mNGS could serve as a valuable complement to conventional diagnostic approaches in adult patients with severe pneumonia after cardiac surgery, potentially improving diagnostic accuracy and leading to more precise and timely interventions, with significant potential to inform clinical decision-making and enhance patient outcomes.