Relationship Between Cerebral Oximetry,Cerebral Blood Flow And Stump Pressure To Indicate Selective Shunting During Carotid Endarterectomy

Objective:The purpose of this study is to investigate the correlation between regional oxygen saturation changes（?r SO₂）,the mean velocity of middle cerebral arterys(V_mean)and stump pressure（SP）during seletive shunting in catotid endarterectomy（CEA）and verify the effectiveness and availability of r SO₂monitoring to become a criterion for shunting.Methods:Forty-eight consecutive patients who underwent selective CEA surgery in general anesthesia in the hospital from March 2021 to March 2022 were enrolled in this study.Shunting was applied if the reduction in the V_meanvalues after cross-clamping on the ipsilateral side exceeded 50%and the operator deceided.All patients were continuously monitored with heart rate,pulse oxygen oximeter and mean artery pressure.The mean velocity of middle cerebral arterys(V_mean)were monitored and recored by Transcranial doppler（TCD）.Regional oxygen saturation（r SO₂）and?r SO₂during cross-clamping one minute were monitored and recored by near infrared spectroscopy（NIRS）.?r SO₂（%）=100×(r SO_2阻断后-r SO_2基础值)/r SO_2基础值.Shunting patients also monitored stump pressure（SP）,which measure the distal interal carotid artery pressure.Complications occured in the inquiry of medical records 7 days after operation,include myocardial infraction,transientischemic attack,stroke,cerebral hyperperfusion syndrome and die.The correlation between?r SO₂,V_meanand SP results was evaluated by pearson correlation analysis.ROC analysis was performed assessing the optimal cut-off point in?r SO₂（%）,sensitivity,specificity and the Youden’s index.Fisher exact test was used to compare and analyze the complication rate of different shunting methods.Results:Applying TCD monitoring results as a criterion for shunting,fifteen patients needed insertion of a shunt（group A）,while nine patients was not necessary（group B）.Applying surgeon preference as a criterion for shunting（group C）.Twenty-four patients（group A and group B）were monitored by?r SO₂and V_mean,a negative,first-order linear association between?r SO₂（%）and V_meanwas documented（r=-0.5811,P=0.0029）.Thirty-nine patients（group A and group C）were monitored by?r SO₂and SP,a negative,first-order linear association between?r SO₂（%）and SP was documented（r=-0.4831,P=0.0018）.Twenty-four patients（group A）were monitored by V_meanand SP,a positive,first-order linear association between V_meanand SP was documented（r=0.6303,P=0.0118）.Using ROC analysis,V_mean>50%was a threshold for shunting,an optimal?r SO₂（%）cutoff value of a 5.99%decrease,with an area under the curve of 0.826（95%CI 6.48-10.00）,P=0.009.The sensitivity,specificity and the Youden’s index were80.0%,88.9%,69.0%.SP≤40mm Hg was a threshold for shunting,an optimal?r SO₂（%）cutoff value of a 5.38%decrease,with an area under the curve of 0.697（95%CI 5.32-8.63）,P=0.036.The sensitivity,specificity and the Youden’s index were 94.4%,42.9%,37.0%.The outcome of different monitoring to indicate shunting criterions included myocardial infarction,TIA,stroke,CHS and death,and there was no significant difference among these groups.Moreover,the?r SO₂（%）,SP and V_meandid not significantly differ from the contralateral ICA with or without severe stenosis in all shunting patients（P>0.05）.Conclusion:We found that the significant correlation between regional oxygen saturation changes（?r SO₂）,the mean velocity of middle cerebral arterys and stump pressure during seletive shunting in catotid endarterectomy under general anesthesia.?r SO₂（%）≤5.99%as a threshold for shunting could serve as a favorable monitoring tool safely.