Impact of transient decrease in mixed venous oxygen saturation on prognosis in off-pump coronary artery bypass surgery: a retrospective cohort study

Abstract

Background The prognostic consequences of transient hemodynamic deterioration due to cardiac displacement, which is most severe during left circumflex artery (LCX) grafting in off-pump coronary artery bypass surgery (OPCAB) are unknown. This study aimed to investigate the association between mixed venous oxygen saturation (SvO2) 24 h, cerebrovascular accident, and acute kidney injury. Results Among 1,071 patients, the composite of morbidity endpoints occurred in 303 (28%) patients. SvO2 < 60% during LCX grafting was significantly associated with the composite of morbidity (OR: 2.72, 95% CI [1.60, 4.61], P < 0.001) along with advanced age, chronic kidney disease, ratio of early mitral inflow velocity to mitral annular early diastolic velocity, and EuroSCORE II. Other major hemodynamic variables including the cardiac index were not associated with the outcome. Additional regression analysis revealed pre-operative anemia as a predictor of SvO2 < 60% during LCX grafting (OR: 2.09, 95% CI [1.33, 3.29], P = 0.001). Conclusions A decrease in SvO2 < 60%, albeit confined to the period of cardiac displacement, was associated with a 2.7-fold increased risk of detrimental outcomes after OPCAB, implying the prognostic importance of this transient deterioration in oxygen supply-demand balance.

Keywords

• cardiac surgical procedures
• hemodynamic monitoring
• off-pump coronary artery bypass
• oxygen saturation
• prognosis
• retrospective study