Time-dependent responses of brain injury biomarkers after severe cerebral desaturation in paediatric patients during cardiac surgery with cardiopulmonary bypass: a single-centre observational cohort study.

BACKGROUND: Neurological injury remains an important concern in paediatric patients after congenital heart disease (CHD) surgery with cardiopulmonary bypass (CPB). Regional cerebral oxygen saturation (rScO2) can be used to identify unstable intraoperative cerebral oxygenation, but its association with the postoperative responses of brain injury biomarkers remains unclear. METHODS: This single-centre observational cohort study included 104 children who underwent congenital heart surgery with CPB. The maximum intraoperative decrease in rScO2 was calculated as the preoperative value minus the lowest value recorded during bypass, during aortic cross-clamping, or after the return of spontaneous circulation. Severe cerebral desaturation was defined as a decrease of at least 20%. The levels of inflammatory cytokines and biomarkers of brain injury were measured preoperatively and on postoperative Days 0 (POD0), POD1, and POD2. Postoperative changes were calculated as log2 fold changes from baseline and z-standardized. The composite inflammation score derived from tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8) levels, and the composite brain injury score derived from glial fibrillary acidic protein (GFAP), S100 calcium-binding protein B (S100B), and neuron-specific enolase (NSE) levels were averaged to derive the composite brain injury score. Adjusted associations were evaluated using multivariable linear regression models, linear mixed-effects models (LMMs), and generalized estimating equations (GEEs), with the non-severe group serving as the reference category. RESULTS: Children in the severe group were younger than those in the non-severe group, but most of the perioperative characteristics were similar. Severe desaturation was not associated with the composite inflammation score. In contrast, severe desaturation was independently associated with a higher postoperative composite brain injury score in both the LMM and the GEEs. The strongest difference between the severe and non-severe groups occurred on POD1 and remained significant after false discovery rate correction. Single-marker analyses showed directionally positive postoperative responses for GFAP, S100B, and NSE. CONCLUSIONS: A maximum intraoperative decrease in rScO2 of at least 20% was associated with postoperative responses of brain injury biomarkers in children who underwent congenital heart surgery with CPB. The association was most evident on POD1 and attenuated by POD2.