In 62 pediatric patients (ages 0–5), children with congenital heart disease (CHD) undergoing cardiopulmonary bypass surgery showed measurably worse gut microbiome profiles even before the operating room — with reduced microbial diversity, elevated pro-inflammatory eicosanoids (notably PGE2), and depleted short-chain fatty acids including butyric acid compared to non-cardiac surgical controls. Post-operatively, these differences intensified: gut barrier dysfunction markers rose, anti-inflammatory cytokines fell, and mediation analysis linked the microbial functional shift specifically to the PGE2 elevation and butyrate reduction driving systemic inflammation.
The finding that dysbiosis precedes surgery — rather than being purely an iatrogenic consequence — is clinically significant. It suggests the CHD disease state itself, possibly through chronic low cardiac output and gut hypoperfusion, reshapes the microbiome long before surgical stress arrives. This reframes gut injury not as a surgical complication to manage reactively, but as a modifiable pre-operative vulnerability.
For the broader microbiome-inflammation field, the PGE2/butyrate antagonism identified here mirrors mechanisms observed in adult inflammatory bowel disease and post-cardiac ICU literature, adding pediatric cardiac surgery as a distinct disease model. Practical implications — whether pre-operative probiotic or dietary butyrate supplementation could reduce post-surgical morbidity — remain speculative at this stage.
Critical limitations: the study is small (only 16 comparison-group patients), observational, and cannot establish causality. As a preprint not yet peer-reviewed, these findings require independent replication before informing clinical protocols.