Monitoring of regional cerebral oximetry by near-infrared spectroscopy during off-pump coronary artery bypass grafting to evaluate the impact on postoperative neurocognitive dysfunction – A prospective study

Abstract

Abstract Background and Aims: Postoperative neurological dysfunction is a common noncardiac complication following cardiac surgery. Primary objective of our study was to evaluate the effects of cerebral oxygen desaturation on the neurological outcome in the postoperative period by monitoring regional cerebral oxygen saturation in off-pump coronary artery bypass grafting (OPCABG). Secondary objective was to study the correlation between regional cerebral oxygen saturation and mean arterial pressure (MAP) during grafting. Setting and Design: It was a prospective observational study in 100 patients of the American Society of Anesthesiologists physical status grading II-III of either sex, having triple vessel coronary artery disease undergoing OPCABG. Patient, having left ventricular ejection fraction (LVEF) <35%, carotid artery disease, on extracorporeal membrane oxygenator or intra-aortic balloon pump, preexisting neurological disorder with standardized mini-mental state examination (SMMSE) score <23, undergoing emergency surgery, re-do surgery, and co-existing valvular diseases were excluded from the study. Surgeries were conducted under general anesthesia with midazolam 0.1 mg/kg, fentanyl 5 μg/kg, and vecuronium 0.1 mg/kg. Anesthesia was maintained with intermittent boluses of fentanyl, vecuronium, and isoflurane. Materials and Methods: The SMMSE was performed preoperatively, 8 and 12 h after extubation. Patients with postoperative SMMSE score of 24–30 were allocated to Group A and patients with SMMSE score ≤ 23, were allocated to Group B. The cerebral oxygen saturation (rSO2), heart rate, MAP, and arterial blood gas were monitored perioperatively. Statistical Analysis: The Chi-square test was used to compare categorical variables and independent Samples t-test was used to compare continuous variables. Pearson bivariate correlation test was used to correlate between the continuous variables. Results: The mean difference of right and left rSo2, between baseline value, and during saphenous vein graft (SVG) to obtuse marginal grafting were 8.70 ± 3.38, 8.78 ± 3.19 in group A and 18.8 ± 2.40, 18.91 ± 1.88, respectively, in group B and were found to be statistically significant. The mean difference of right and left rSO2, between baseline value and during SVG to posterior descending artery grafting were 6.48 ± 3.91, 7.10 ± 3.67 in group A and 18.1 ± 3.57, 17.9 ± 3.60 in group B and were found to be statistically significant. Mean difference and percentage variation from baseline of right and left rSo2 and MAP from preinduction to grafting from left internal mammary artery to left anterior descending artery were found to be statistically insignificant. Conclusion: A decrease of regional cerebral saturation value by 25% from baseline or an absolute reduction of rSO2 value by 50% and reduction in MAP from baseline, during the period of grafting was associated with postoperative neurocognitive dysfunction.