Effect Of Therapeutic Hypercapnia On Brain Oxygenation Metabolism In Patients Undergoing Thoracoscopic Surgery On The Beach Chair Position

Objective:To evaluate the effect of therapeutic hypercapnia on brain oxygenation metabolism in patients undergoing endoscopic thoracic surgery with CO2 pneumothorax on the beach chair position.Methods:Sixty patients of palmar hyperhidrosis undergoing elective bilateral thoracoscopic sympathectomy,of both sexes,aged 16～32 yr,with body mass index of 19～24 kg/m2,of American Society of Anesthesiologists physical status I or II,were randomly divided into two groups with 30 patients in each group using a random number table.All patients in both groups were performed with general anesthesia with tracheal intubation by low tidal volume(VT 6ml/kg)intermittent positive pressure ventilation combined with low level of positive end expiratory pressure(PEEP=5cmH2O),maintaining PaCO2 at 35～45mmHg.PaCO2 value was maintained at a level of 35～45mm Hg in group C and of 45～55 mmHg in group H by adjusting respiratory rate after patients were put on beach chair position.BIS value was kept at a level of 40～60 by adjusting the plasma target concentration of propofol during maintenance of anesthesia.Before anesthesia induction(T0),at 5 min after intubation(T1),and at 5,10,15 and 20 min after the patients were placed on the BCP(T2-5),the MAP、HR、SpO2、BIS value were recorded,and blood samples were taken from the radial artery and jugular bulb for blood gas analysis,arteriovenous blood O2 content difference,cerebral O2 extraction rate,and venous to arterial blood lactate content difference were calculated.The development of hypotension(MAP values of<20%from baseline values)、SjvO2<50%、cerebral oxygen desaturation(SjvO2<50%last more than10 minnutes)and the total consumption of phenylephrine were assessed,and the extubation time、time for oriention recovery were also recorded.Results:Patients’ demographic and historic variables were similar between groups including age,gender,BMI,ASA status,previous surgery and smoking(P>0.05).There were no significant differences between groups in the terms of surgeon,operation time,intraoperative blood loss and intraoperative fluid replacement(P>0.05).No significant differences were found in the terms of anesthetist,anesthesia time,extubation time,oriention recovery time,the total consumption of propofol,the total consumption of sufentanil and the total consumption of rocuronium(P>0.05).No significant differences were found in MAP,SpO2,HR and BIS value between the two groups at the corresponding timepoint(P>0.05).In the Group C,no significant differences were found in PaCO2、SjvO2、Da-jvO2、and CERO2 at T2,T3,T4,T5 compared that at T1(P>0.05).In the Group H,PaCO2、SjvO2 at T2,T3,T4,T5 were significantly higher than that at T1,while Da-jvO2、CERO2 at T2,T3,T4,T5 were significantly lower than that at T1(P<0.05).Compared with group C,PaCO2、SjvO2 at T2,T3,T4,T5 were significantly higher and Da-jvO2、CERO2 were significantly lower in group H(P<0.05).The incidence of hypotension in group C and group H were 57%and 53%respectively,no significant difference between the two groups(P>0.05);SjvO2<50%was found in group C at T2 with 6 cases(20%),and was not found in group H,the incidence was significantly lower than group C(P<0.05);and no cerebral oxygen desaturation was found in both groups.All cases were successfully completed the surgery without complications occurred.Conclusion:Therapeutic hypercapnia can improve the brain oxygenation metabolism of patients undergoing endoscopic thoracic surgery with CO2 pneumothorax on the beach chair position,is worthy of promotion in clinical as its safty.