The Effects Of The Regional Cerebral Oxygen Saturation On Postoperative Cognitive Function And Prognosis Of The Patients Undergoing Off-pump Coronary Artery Bypass Graft

Objective: To observe changes of the regional cerebral oxygen saturation（rSO₂）during OPCABG operation,and to evaluate its influences on postoperative cognitive dysfunction and prognosis.This study would provide evidences for the clinical applications of rSO₂.Methods:From January 2016 to December 2016,50 patients were scheduled for elective off-pump coronary bypass,ASA class Ⅲ or Ⅳ,male 44 and female6.The patients combined with diabetes were 13 and hypertension were 30 preoperative,30 cases of cardiac functional grading of level 2 and 20 cases of level 3.All of the patients preoperative hemoglobin were in normal range,liver and kidney function were not found obvious abnormity.We defined the cerebral anoxia as the absolute rSO₂ below 50% or a decrease in the relative rSO₂ of 20% compared with the individual baseline value.If the absolute rSO₂ below 50% or a decrease in the relative rSO₂ of30% compared with the individual baseline value occurred,and then increased blood pressure to improve rSO₂.The patients were divided into 2 groups according to brain hypoxia existed or not,with brain hypoxia existed were set to H group,without were set to N group.The patients’ cognitive function was valuated with MoCA the day before surgery.If the education years were less than 12 years and then the MoCA scores plus 1 point.Cognitive dysfunction defined as the MoCA test scores <26 points or reduction of 2 points compared with the preoperative.Blood pressure（BP）,heart rate（HR）,pulse oxygen saturation（SpO2）,double-frequency index（BIS）,end-tidal CO2 pressure（PETCO2）,temperature（Temp）,central venous pressure（CVP）and rSO₂ were the regular monitors.When severe hypotension or cardiac arrhythmias occurred and could not satisfy the whole-body perfusion after corrected it actively,and then changed to on-pump coronary artery bypass graft.Autologous blood transfusion was used to maintain patients’ hemoglobin > 10 g/L,and the temperature was maintained at 36.0 to 37.5 ℃.Effective sedation and analgesia were given after operation,and controlled breath back to the cardiac surgical ICU.BP、HR、SpO2、rSO₂、BIS、PETCO2、Temp and CVP were recorded respectively at the time of being in the operation room,immediately after intubation,before dividing left breast inside arteries,the ending of bypass operation process（left anterior descending coronary artery,right coronary artery,circumflex branch/the first branch,aorta side wall clamp）,closed chest,the ending of operation.Recorded the patients’ MoCA scores 1 week and1 month after operation,and prognosis — include : severe neurological complications,extubation time,ICU length of staying and postoperative hospital stay.Severe neurological complications included: cerebral infarction,cerebral hemorrhage,coma and new cases of epilepsy.If the cerebral anoxia occurred,the condition and the time of duration were recorded.If special circumstance occurred（such as ventricular fibrillation）and then recording the situation at that time and the time of duration.The patients were divided into 2groups according to brain hypoxia existed or not,with brain hypoxia existed were set to H group,without were set to N group.Results: All of the patients（n=50）were completed under off-pump operation,and recovered well.The cases of rSO₂ decreased more than 20% of the baseline during the operation were 9,brain hypoxia existed（H group,n=9）;the cases of rSO₂ decreased less than 20% of the baseline during the operation and absolute value > 50% during the operation were 41,brain hypoxia didn’t exist（N group,n=41）.The rSO₂ decreased more than 30% of the baseline or the absolute > 50% during the operation didn’t occur.All the patients completed the MoCA test 1 week after surgery,and 45 cases complete 1month after surgery;4 cases lost to follow-up of the N group,and 1 case lost to follow-up of the H group.1 week and 1 month after surgery,there were noone of the MoCA scores < 26 points or compared with preoperative reduce 2points.The preoperative conditions of the two groups might affect the cerebral hypoxia occurred or not did a analysis with logistics regression,and found that age,gender,BMI,hypertension,diabetes,heart function,the number of coronary artery lesions were no effects on the cerebral hypoxia occurred or not.Analysis of rSO₂ and MAP,found that rSO₂ and MAP show positive correlation,the coefficient was 0.601,P <0.05.Analyzed the conditions of H group,and found that brain hypoxia occurred when the bypass operation process were matching the right coronary artery（4 cases）and the posterior interventricular branch（4 cases）,and ventricular fibrillation（operation process of matching the first branch 2 cases and the posterior interventricular branch 1case）occurred during the operation（3 cases）,the mean time was 7.64 ± 0.81 mins.The brain hypoxia occurred twice in 2 cases,during the operation of matching the right coronary artery and the posterior interventricular branch,the duration time was 15.50±0.71 mins.3 cases met with ventricular fibrillation during the operation,when the cardiopulmonary resuscitation（CPR）in the chest were going on,the minimum of the rSO₂ were 58,60 and 60 respectively,and the percent of reduction were 21%,22% and 22% respectively.The 3 cases of ventricular fibrillation recovered sinus rhythm within 1min after timely correction,but the value of the rSO₂ gone well slowly,and the duration time of brain hypoxia was 7.67±0.58 mins.All of the patients met without POCD,without serious neurological complications.The decrease of the relative rSO₂ >20% of the baseline and the duration of 7-8mins during the operation,this had no significance effect on postoperative cognitive function.Compared the prognosis of the two groups: extubation time and ICU length of staying of the H group were longer compare with N group,and the difference was statistically significant（P <0.05）;postoperative hospital stay were no statistically significant（P>0.05）.Conclusions:1 The rSO₂ can not predict the occurrence of POCD and serious neurological complications efficiently during OPCABG operation.2 The decrease of the relative rSO₂ >20% of the baseline value,the extubation time and ICU length of staying will be longer.3 The relative rSO₂ is maintained within 20% of the baseline during OPCABG operation,postoperative extubation time and ICU length of staying time will shorten.