Effect Of Different Ventilation Modes On The Diameter Of Optic Nerve Sheath In Elderly Patients Undergoing Laparoscopic Colorectal Cancer Surgery

Objective:To observe the changes in optic nerve sheath diameter（ONSD）in elderly patients undergoing laparoscopic colorectal cancer surgery under pressure controlled ventilation（PCV）and volume controlled ventilation（VCV）with ultrasound,indirectly reflect the effects of the two ventilation modes on intracranial pressure and provide more appropriate ventilation options for perioperative brain protection.Methods:Sixty patients who underwent laparoscopic resection of rectal and sigmoid colon tumors were selected,including 31 males and 29 females,aged 60-80 years,ASA II grade,BMI 18.5-28 kg/m²,and they were randomly divided into groups V and P by random number table method.Group V used VCV ventilation mode,and group P used PCV ventilation mode.Recording the cross-sectional and sagittal average ONSD values of left and right eyes before induction of anesthesia（T₀）,10minutes after induction of anesthesia in the supine position（T₁）,establishment of the CO₂pneumoperitoneum Trendelenburg position for 10 minutes（T₂）,60 minutes（T₃）,and the disappearance of the pneumoperitoneum and 10 minutes after the supine position（T₄）;Recording the peak airway pressure（Ppeak）,mean airway pressure（Pmean）,Pa CO₂,P_ETCO₂,Pa O₂,dynamic lung compliance（Cdyn）at T₁-T_4,and HR,MAP,CVP,Sp O₂at T₀-T₄;The Mini-mental state Examination scale（MMSE）was recorded one day before surgery and one and three days after surgery,and the incidence of nausea and vomiting,dizziness,headache and pulmonary complications were recorded 3 days after surgery.Results:1.There was no statistical significance in the comparison of general information between the two groups（P>0.05）.2.Comparison of optic nerve sheath diameter:there was no statistically significant difference in ONSD between the two groups at T₀and T₁（P>0.05）.Compared with T₁,the mean value of ONSD in two groups at T₂-T₄was significantly increased（P<0.05）.Compared with T_3,the mean ONSD of the two groups at T₄decreased significantly（P<0.05）;Compared with group V,the mean value of ONSD at T₂-T₃in group P was significantly smaller（5.32±0.11mm vs 5.38±0.10mm,5.48±0.10mm vs 5.57±0.12mm,P values were 0.028 and 0.006,respectively）.3.Comparison of respiratory parameters:compared with T₁,Pmean and P_ETCO₂were significantly increased and Pa O₂were significantly decreased at T₂-T₃（P<0.05）,Ppeak and Pa CO₂were significantly increased and Cdyn was significantly decreased at T₂-T₄（P<0.05）.Compared with group V,Ppeak and Pa CO₂in group P were significantly decreased at T₂-T₃（P<0.05）,while Pa O₂and Cdyn were significantly increased（P<0.05）.4.Comparison of hemodynamic parameters:there were no statistically significant differences in HR,MAP and Sp O₂between the two groups at T₀-T₅（P>0.05）.Compared with T₁,CVP was significantly increased in both groups at T₂-T₃（P<0.05）.Compared with group V,CVP in group P was significantly decreased at T₂-T₃（P<0.05）.5.MMSE score for evaluation of postoperative cognitive dysfunction:MMSE score of 1 day before surgery,1 day after surgery and 3 days after surgery in 2 groups was not statistically significant（all P>0.05）.6.Postoperative complications:There was no statistical significance in postoperative nausea,vomiting,dizziness,headache and pulmonary complications in2 groups（all P>0.05）.Conclusion:During laparoscopic colorectal cancer surgery,the pneumoperitoneum and Trendelenburg position will significantly increase the intracranial pressure of the patient.Compared with volume-controlled ventilation,pressure-controlled ventilation can effectively relieve the increase in intracranial pressure caused by pneumoperito-neum and Trendelenburg position.