Is thiol/disulfide homeostasis an early predictor of postoperative neurocognitive dysfunction in near infrared spectroscopy-guided coronary artery bypass surgery patients: A prospective study

Introduction In cardiac surgery, cerebral dysfunction due to intraoperative cerebral microembolism, hypoperfusion, low perfusion pressure, hypothermia and rewarming is one of the most frequent morbidities in the postoperative period and results in tissue hypoxia and reperfusion damage. Given the possible link among oxidative stress and neurocognitive dysfunctions, we hypothesized that dynamic thiol-disulfide homeostasis could be an early predictor of cognitive impairment in cardiac surgery in parallel to the changes in cerebral oxygenation. Methods Seventy-one patients undergoing elective coronary artery bypass graft (CABG) surgery were prospectively studied. The patients were assesed by Mini-Mental State Examination (MMSE) test, pre and postoperatively. In the operating room, following standard monitorization, a near-infrared spectroscopy (NIRS) sensor was placed for continuous measurement of regional cerebral oxygenation (rSO 2 ). The blood samples were obtained for thiol/disulphide homeostatic (TDH) parameters at 5 stages of the surgical procedure as; T 1 : before anesthesia induction; T 2 : 20 min after anesthesia induction, T 3 : 20 min after aortic cross-clamping; T 4 : 20 min after removal of aortic cross-clamp; and T 5 : 24 h after surgery. Results Postoperative 24 hours’ MMSE scores were significantly lower than the preoperative scores ( p < .001). Total and native thiol measurements were significantly higher at T 5 in comparison to T 2 , T 3 and T 4 ( p < .001). Conclusion Although abnormal TDH values are involved in the pathogenesis of various diseases, we couldn’t show that TDH was an early predictor of neurocognitive dysfunction after CABG surgery, the changes in total, native thiol and disulphide levels were in parallel with changes in NIRS values, indicating the changes observed as a result of anesthesia induction, IR injury and postoperative course. As this is the first study evaluating TDH changes as a predictor of ischemia-reperfusion injury in CABG by evaluating NIRS and MMSE scores, we believe that our study will enlighten the current literature.