Clinical Observation Of Regional Cerebral Oxygen Saturation In Patients Undergoing Off-pump Coronary Artery Bypass Grafting

Objective:By observing the changes of regional cerebral oxygen saturation（rSc O₂）during off-pump coronary artery bypass grafting（OPCABG）,the purpose of this study was to evaluate the application value of cerebral oxygen saturation monitor in OPCABG and the improvement of cerebral oxygen after the application of norepinephrine to correct hypotension.Method:Sixty-one patients who underwent OPCABG in the department of cardiac surgery,the second hospital of Hebei Medical University from March 2019 to December 2019 were selected.The invasive arterial blood pressure and rSc O₂were continuously monitored,and several time points before the initiation of anesthesia induction,after the completion of anesthesia induction and when the intraoperative circulation had significant fluctuations were selected to record their mean arterial blood pressure（MAP）and rSc O₂.Meanwhile,the central venous blood gas was sent for examination at the time point of the appeals and the central venous oxygen saturation（Scv O₂）value at the corresponding time point was recorded.When systolic blood pressure（SBP）<90mm Hg or MAP<60mm Hg,give rehydration,adjust the position,push norepinephrine 4-12ug if necessary,correct hypotension,and record the values of MAP and rSc O₂ before and after norepinephrine.Results:Two hundred and seventy groups containing MAP,rSc O₂ and Scv O₂ data were collected from 61 cases.The maximum value of MAP（78.10±20.51mm Hg）was 144mm Hg,the minimum value was 38mm Hg,and the median value was 75mm Hg.The maximum value of rSc O₂（68.96%±6.31%）was 82%,the minimum value was 48%,and the median value was 69%.The maximum value of Scv O₂（69.46%±8.99%）was 87.2%,the minimum value was 40.6%,and the median value was 70.5%.The data of270 group rSc O₂ and MAP were drawn into a scatter diagram,and the correlation analysis was conducted.The results showed that rSc O₂ was positively correlated with MAP with a low degree of linearity（r=0.493,P<0.001）.The data of 270 group rSc O₂ and Scv O₂ were drawn into a scatter diagram,and analyzed for correlation.The results showed a moderate linear positive correlation between rSc O₂ and Scv O₂（r=0.640,P<0.001）.The consistency analysis of 270 rSc O₂ and Scv O₂ data was performed by Bland-Altman analysis,the results showed that the bias range of rSc O₂ and Scv O₂ was（-0.5%±6.93%）,the 95%consistency threshold was（-14%-13.1%）,the data points outside the 95%consistency threshold accounted for 4%（12/270）of the total,the data points inside the consistency threshold accounted for 96%（258/270）of the total,and the maximum absolute value of the difference within the consistency threshold was 13.5.A total of 34 of the 61patients were given norepinephrine to raise their blood pressure.After the application of norepinephrine,MAP（68.91±6.91mm Hg）was increased（13.77±5.24mm Hg）compared with the former（55.15±5.76mm Hg）,and the change of MAP before and after the treatment was statistically significant（P<0.001）;rSc O₂（63.41%±5.00%）was changed（-1.32%±2.35%）after norepinephrine was applied（64.74%±5.13%）,and the change of rSc O₂ before and after norepinephrine was statistically significant（P=0.002）.Conclusions:1.In OPCABG,changes in MAP cannot be relied on to accurately evaluate changes in rSc O₂,and cerebral oxygen monitor is recommended to monitor and optimize oxygenation in cerebral tissues.In the absence of a cerebral oxygen monitor,Scv O₂ can be used to roughly evaluate rSc O₂.2.In our observations,norepinephrine is not found to improve the cerebral oxygen when correcting hypotension.