Background

Postoperative delirium (POD) is a common complication of cardiac surgery with cardiopulmonary bypass (CPB), and it is associated with systemic inflammation and gut–brain axis dysregulation. This study investigated the intestinal microbiota dynamics in patients with POD undergoing CPB to identify microbiota-related biomarkers and associated mechanisms.

Methods

This observational study included 48 patients who underwent cardiac valve surgery with CPB. Faecal samples were collected preoperatively and postoperatively. POD was diagnosed using the Confusion Assessment Method for the Intensive Care Unit and 3-minute Diagnostic Confusion Assessment Method within 7 days of surgery. The intestinal microbiota composition was analysed using 16S rRNA sequencing, and the alpha/beta diversity, taxonomic groups, and functional pathways were then evaluated. Perioperative variables and microbiota differences between the POD and non-POD (NPOD) groups were evaluated.

Results

In patients with POD, the postoperative intestinal microbiota exhibited reduced alpha diversity (e.g., observed amplicon sequence variants, P < 0.001) and altered beta diversity (unweighted or weighted UniFrac, P < 0.001) than those in preoperative samples. Linear discriminant analysis Effect Size analysis identified 25 differentially expressed species that served as biomarkers (linear discriminant analysis score > 4). Preoperatively, no significant differences in the microbial communities were found between the POD and NPOD groups (unweighted UniFrac, P = 0.171; weighted UniFrac, P = 0.085). Postoperatively, patients with POD exhibited distinct beta diversity (unweighted UniFrac, P = 0.004; weighted UniFrac, P < 0.001), and Lactobacillaceae was identified as a protective biomarker. Further, CPB period was an independent risk factor for POD (Odds ratio, 1.06 [95% confidence intervals, 1.01–1.14]) .

Conclusion

This study demonstrates significant alterations in the intestinal microbiota composition following cardiac valve surgery with CPB and reveals that Lactobacillaceae is a potential protective biomarker for POD.