Post-operative cerebral oximetry for detection of low-cardiac output syndrome after coronary artery bypass surgery

While cerebral near infrared spectroscopy (NIRS) is a valuable diagnostic tool to monitor brain oxygenation during cardiac surgery, its value in low cardiac output syndrome (LCOS) in adults has not been evaluated. This study was prospective and observational. Patients undergoing coronary artery bypass grafting (CABG) with reduced ejection fraction (LVEF < 35%) were included and received NIRS monitoring for up to 48 h after surgery with simultaneous continuous cardiac index (CI) monitoring. The primary endpoint was LCOS by a standard definition. From 2020 to 2023, 82 Patients with severely reduced LVEF undergoing CABG were included. Of these, 44 patients had sufficient NIRS and CI data for further analyses. Median age was 68 years (Interquartile range (IQR) 60-73), 91% (40/44) were male and median EuroSCORE II was 3.2% (1.7-5.4). Median LVEF was 30% (26.5-30.1) and baseline CI was 2.15 L/min/m² (2.05-2.60). CABG was combined with other procedures in 23% (10/44). LCOS rate was 11% (5/44) and in-hospital mortality was 2.2% (1/44). The performance of Lasso-regularized models increased if NIRS was included in LCOS prediction models (AUROC 0.99 [95%CI, 0.98-1.00]) showing that both relative NIRS drop rate and absolute NIRS value were significant predictors of LCOS. Risk of LCOS was high if NIRS drops by > 20% or absolute NIRS drops below < 50. In patients with LCOS, NIRS drop occurred before CI values decreased. NIRS drop was not associated with other adverse events. NIRS is an early and valid indicator of LCOS in patients after cardiac surgery. In selected patients, NIRS may be a substitute for invasive continuous CI measurements. However, we could not show an association of NIRS drop with adverse events. Future studies should compare blinded and non-blinded NIRS monitoring to investigate possible impact on clinical outcomes further.