Background: 

Infants with congenital heart disease (CHD) frequently undergo surgery during their first year of life. Infants undergoing CHD surgery experience systemic inflammation and haemodilution that can deplete circulating immunoglobulins (Ig).

Methods: 

In this prospective single-centre observational cohort study without healthy controls, we quantified IgG, IgA and IgM at four peri-operative time-points (T0 = pre-op; T1 = 24 h; T2 = 72 h; T3 = day 7) in 300 infants (<12 months), including 280 with CPB and 20 without CPB. Post-operative infections were defined using CDC/NHSN cardiothoracic criteria. Multivariable logistic and linear models assessed associations between Ig depletion, cardiopulmonary bypass (CPB) characteristics and clinical outcomes.

Results: 

Mean IgG fell 23% at T1 (910 ± 160→700 ± 140 mg dL⁻¹, p<0.001) and partially recovered by T3. Longer CPB was independently related to larger IgG decline (β = 2.5% per 10 min, p<0.001; R² = 0.14). Infection occurred in 17% of infants and was associated with lower IgG at T1 (650 ± 135 vs 725 ± 140 mg dL⁻¹, p<0.001) and prolonged ICU stay (median 7 vs 5 days, p<0.01). Baseline IgG < 900 mg dL⁻¹ (aOR 2.1), CPB > 120 min (aOR 2.5), gestation < 37 weeks (aOR 1.9) and surgical complexity (RACHS-1 ≥ 3; aOR 1.8) independently predicted infection.

Conclusions: 

Substantial early-post-operative IgG depletion correlates with infection risk and ICU utilisation after infant CHD surgery. Routine peri-operative Ig monitoring may help stratify risk and identify candidates for immunoglobulin-based interventions.