This study investigates the impact of oxygen delivery (DO2) during cardiopulmonary bypass (CPB) on major clinical outcomes in cardiac surgery patients. Maintaining adequate DO2 during CPB is essential for end-organ perfusion, potentially reducing complications like acute kidney injury (AKI) and improving recovery. This retrospective analysis included 845 adult patients undergoing isolated coronary or valve surgeries between January 2021 and March 2023. DO2 values were measured every 30 minutes during CPB, and patients were grouped based on DO2 levels: Group A (all readings ≥280 mL O2/min/m²), Group B (at least one reading <280 mL O2/min/m²), and Group C (two or more readings <280 mL O2/min/m²).
The study found significant differences in clinical outcomes based on DO2 levels. Group A patients, with consistently high DO2, experienced the best outcomes. They had shorter postoperative hospital stays (5.2 days) compared to Group B (6.6 days) and Group C (7.0 days). Prolonged ventilation occurred in only 3.2% of Group A patients, while 7.4% of Group B and 9.2% of Group C patients required extended ventilation. These results suggest that maintaining DO2 above 280 mL O2/min/m² during CPB promotes faster recovery and reduces the risk of prolonged ventilation.
Although unadjusted analyses showed that Groups B and C had higher rates of AKI compared to Group A, this association did not reach statistical significance in multivariable models. In the unadjusted data, AKI rates were 12.1% in Group A, 23.3% in Group B, and 27.0% in Group C. Other postoperative complications, such as renal failure, stroke, deep sternal wound infection, and reoperation rates, showed no significant differences between groups.
Multivariable regression analyses confirmed that DO2 levels independently influenced outcomes like prolonged ventilation and hospital length of stay. Specifically, patients with higher DO2 were less likely to experience prolonged ventilation or extended hospital stays, even after accounting for factors such as age, preoperative hemoglobin, creatinine levels, and CPB time. However, the relationship between DO2 and AKI, while trending towards significance, did not meet the threshold for statistical confirmation in this study.
Patients in Group A were generally healthier and had fewer risk factors, including lower preoperative creatinine levels and higher hemoglobin levels, which could have contributed to their better outcomes. The study also highlighted that low DO2 levels often correlated with higher-risk patient profiles, as reflected by the Society of Thoracic Surgeons (STS) Predicted Risk of Mortality scores. Group A had the lowest predicted risk (1.2%), while Group B and Group C had higher scores (1.9% and 3.1%, respectively).
The findings emphasize the importance of goal-directed perfusion strategies during CPB to optimize oxygen delivery. By maintaining DO2 levels above 280 mL O2/min/m², clinicians can reduce recovery times and ventilation requirements. The study aligns with prior research linking DO2 to improved outcomes but expands on this by demonstrating its independent effect on recovery metrics. It also underscores the need for further investigation into the optimal DO2 threshold and duration, particularly for high-risk patients.
Despite its insights, the study has limitations. As a retrospective analysis, it is subject to potential confounding factors and bias. Additionally, the relatively low overall incidence of AKI (16%) may have limited the ability to detect statistically significant associations with DO2 in multivariable models. Moreover, the study did not analyze the cumulative time spent below the DO2 threshold, which could provide further insights into its impact on outcomes.
In conclusion, this study highlights the critical role of maintaining adequate oxygen delivery during CPB to enhance postoperative recovery. High DO2 levels are associated with reduced rates of prolonged ventilation and shorter hospital stays, supporting the implementation of goal-directed perfusion strategies. However, further randomized trials are needed to refine these thresholds and validate the findings across broader patient populations and surgical contexts.
