Study On Cerebral Protection Of Permissive Hypercapnia In Patients Undergoing Shoulder Arthroscopic Surgery Under Controlled Hypotension

Objective:To study the cerebral protective effect of permissive hypercapnia on patients undergoing shoulder arthroscopic surgery in the supine position with controlled hypotensionMethods:Sixty-four patients undergoing elective shoulder arthroscopy were included and randomly divided into two groups（n=32）as the general ventilation group（C group）and the hypercapnia group（H group）respectively.All patients underwent standard monitoring after entering the room.Radial artery catheterization was performed on the healthy side,and brachial plexus block（intermuscular groove method）was performed on the affected side.Mechanical ventilation was performed after induction of general anesthesia,and the ventilation strategy was changed 15 minutes after tracheal intubation（maintaining PaCO₂35-45 mm Hg in group C and PaCO₂45-55 mm Hg in group H）.Changes in MAP,rSO₂ and PaCO₂ were recorded before induction of anesthesia（T₁）,15 min after tracheal intubation（T₂）,at the beginning of surgery（T₃）,30 minutes after the start of the surgery（T₄）and 5 min after surgery（T₅）,respectively.Serum levels of neuron-specific enolase（NSE）,brain-derived neurotrophic factor（BDNF）,tumor necrosis factor-α（TNF-α）and C-reactive protein（CRP）were measured by enzyme-linked immunosorbent assay（ELISA）at admission and 24 hours after operation.The neuropsychological tests were performed on the patients before and 24 hours after operation with the simple intelligent mental state examination scale to evaluate the effect of permissive hypercapnia on brain protection and postoperative cognition in patients undergoing shoulder arthroscopy in lateral position under controlled hypotension.Results:1.There was no significant difference in general data between the two groups（P>0.05）.2.There was no statistically significant difference between the two groups in terms of MAP at each time point（P>0.05）;compared with group C,PaCO₂ was higher in group H at T₃,T₄ and T₅,and the difference was statistically significant（P<0.05）;compared with group C,rSO₂ was higher in group H at T₃ and T₄,and the difference was statistically significant（P<0.05）.3.Comparison of NSE,TNF-α,CRP and BDNF concentrations:Comparison within the group:The concentrations of NSE,TNF-αand CRP in the two groups were significantly higher than those before operation（P<0.05）.The concentration of BDNF in group C was significantly lower than that before operation（P<0.05）.Comparison between groups:There was no difference in NSE concentration,BDNF concentration,TNF-αconcentration and CRP concentration between the two groups before operation（P>0.05）.The concentrations of NSE,TNF-αand CRP in group C were significantly higher than those in group H（P<0.05）.The concentration of BDNF was significantly decreased（P<0.05）.4.There was no statistically significant difference in postoperative adverse reactions（nausea,vomiting,and hypotension）between the two groups of patients,as well as in the scores of the Simple Intelligent Mental State Examination Scale between the two groups（P>0.05）.Conclusions:Permissive hypercapnia can improve cerebral oxygen metabolism and reduce neuroinflammatory response in patients undergoing shoulder arthroscopic surgery in lateral position under controlled hypotension,which has a certain brain protection effect.