The Journal of ExtraCorporeal Technology No 57-2 | Page 29

80 K. Kırali et al.: J Extra Corpor Technol 2025, 57, 74 – 81

Table 7. Mechanical ventilation and length of stay in ICU comparison.

MiECC, Minimal Invasive Extracorporeal circulation; ICU, Intensive Care Unit.

Discussion

This study compares the HS and MiECC systems in patients undergoing isolated CABG. With matched demographic and clinical characteristics across groups, including age, gender distribution, body surface area, and left ventricular ejection fraction any observed differences can more confidently be attributed to the performance of the HS versus MiECC in the perioperative setting; in a sense, HS is no inferior to MiECC.

A primary outcome was the CPB time, which, though not reaching statistical significance( p = 0.134), was shorter in the HS-group compared to the MiECC group( 93.35 ± 33.06 min vs. 108.65 ± 30.02 min). Shorter CPB durations are clinically advantageous, as prolonged CPB times are associated with higher risks of inflammation and potential complications [ 3, 4 ]. In this context, the HS may offer a time-efficient alternative to the MiECC technique without compromising the safety and quality of care. Both groups requiring a similar number of anastomoses and exhibited comparable hemoglobin levels at all-time points-preoperative, perioperative, and postoperative( at 6, 12 and 24 h) – suggesting that oxygen carrying capacity was similarly managed.

No significant difference in transfusion requirements was observed between the HS and the MiECC. This transfusion strategy likely reflects specific institutional practices and patient profiles, which may differ from those of other centers. In our institution, the transfusion trigger generally aligns with the nadir hemoglobin level, which is influenced by patient-specific factors such as age, comorbidities, and clinical status [ 7 ]. According to current literature, transfusion triggers in cardiac surgery often range from haemoglobin levels of 7 – 8 g / dL, depending on the patient’ s hemodynamic stability and risk profile [ 3, 5 ]. These variations in transfusion practices and patient selection criteria across institutions can significantly impact transfusion rates, as also observed in multi-center registries. In terms of oxygenation, the HS achieved an indexed oxygen delivery( DO 2 i) of 311.60 ± 28.29 mL / min / m 2, which, while not statistically superior to the MiECC group( 332.25 ± 57.04 mL / min / m 2, p = 0.275), highlights the HS’ s capability to maintain stable oxygenation. Notably, the PaO 2 was higher in the MiECC-group, because HS-group used PaO 2 monitoring control with Quantum Ventilation Module by Spectrum medical to prevent the deleterious effects of hyperoxia( 210.90 ± 49.64 mmHg vs. 177.70 ± 70.41 mmHg, p = 0.093).

Hyperoxia refers to a state where oxygen levels in the blood or tissues are excessively high. It is generally defined by a PaO 2 above the normal physiological range, typically greater than 100 mmHg. Hyperoxia often occurs when patients receive supplemental oxygen, especially at high concentrations or over prolonged periods, such as during surgery( including CABG with CPB), mechanical ventilation, or emergency care [ 2 ]. In clinical practice, the focus is often on balancing oxygen delivery to avoid hypoxia( low oxygen) while preventing hyperoxia. Excessive oxygen can lead to cellular and tissue damage due to increased production of reactive oxygen species( ROS), contributing to oxidative stress, inflammation, and other complications in both acute and long-term settings [ 1, 4, 5 ].

The HS-group employed hypobaric oxygenation during CPB, aiming to reduce gaseous micro-emboli formation and minimize stress on blood components and the endothelium, while maintaining effective oxygenation, hypobaric oxygenation is achieved by maintaining an oxygen pressure lower than standard levels in the oxygenator [ 8 ].

Biochemical parameters further illustrate differences in tissue response between the two systems. Lactate levels at the 6th hour after CPB was lower in the HS-group( 2.85 ± 1.20 mmol / L vs. 4.04 ± 1.40 mmol / L, p = 0.009), indicating tissue metabolic stability. Similarly, troponin levels indicative of myocardial injury was significantly lower in the HS group at the 6th hours after CPB( 3.188 ± 2.684 ng / mL vs. 4.645 ± 3.422 ng / mL, p = 0.038), suggesting reduced myocardial stress. This difference could be attributed to several specific features of the HS. One potential mechanism is the system’ s stable oxygenation capability. The HS maintains a consistent oxygen delivery due to its dual-chamber design and collapsible soft bag reservoir, which allows for more precise control of oxygenation and blood volume during CPB. This stability reduces fluctuations in tissue perfusion and oxygen supply, which are known contributors to myocardial ischemia and injury, especially in high-risk patients undergoing cardiac surgery.

Additionally, the minimized blood-air interface in the HS further contributes to lower troponin levels by limiting contact between the blood and external surfaces, which helps reduce systemic inflammatory responses. In traditional CPB setups, exposure to foreign surfaces and air can lead to the activation of inflammatory pathways, ultimately increasing oxidative stress and myocardial workload. By minimizing this exposure, the HS likely reduces myocardial oxygen demand and preserves cardiac tissue integrity, resulting in lower troponin release postoperatively. Together, these factors suggest that the HS’ s design supports myocardial protection through enhanced oxygenation stability and reduced inflammatory activation [ 8, 9 ]. Future studies focusing on myocardial injury markers in larger cohorts could further validate these findings and clarify the protective mechanisms inherent in the HS.

However, an interesting contrast was observed in LDH levels and trends, which were lower in the MiECC group during and after CPB compared to the HS group. LDH serves as a marker of cellular damage, and elevated levels may indicate cell stress or injury [ 10 ]. The lower LDH levels in the MiECC