Effects Of A 1:1 Inspiratory To Expiratory Ratio On Respiratory Mechanics And Interleukin-6 In Elderly Patients With Laparoscopy

Objective: Laparoscopic surgery,especially for elderly patients with reduced function of various organs,poses a great risk to anesthes ia and surgery.Pneumoperitoneum and low head position have significant effects on respiratory mechanics,which can cause serious complications such as lung injury.The objective of our study was to observe the effects of 1:1 inspiratory to expiratory ratio on respiratory mechanics and interleukin-6(IL-6)using pressure-controlled ventilation in elderly patients undergoing radical resection of laparoscopic colorectal cancer,aiming to provide a reference for clinical anesthesia management method for gastrointestinal surgery.Methods: Forty patients aged 65~75 years,ASA(American Society of Anesthes iologists,ASA)? or ? level,undergoing laparoscopic radical resection of colorectal cancer were enrolled in the study.The patients were randomly divided into 2 groups.In the group A we used 1:1 I:E ratio after establishing the pneumoperitoneum and changing the posture,and 30 minutes later we switched to a 1:2 I:E ratio.In the group B,we used 1:2 I:E ratio after establishing the pneumoperitoneum and changing the posture,and 30 minutes later we switched to a 1:1 I:E ratio.All patients underwent venous access and intraoperative routine monitoring including electrocardiogram,blood pressure,heart rate,saturation of pulse oximeter,and bispectral index to monitor the depth of anesthesia.Fentanyl 3~5ug/kg,cisatracurium 0.15mg/kg,etomidate 0.2~0.3mg/kg were given for the induction of anesthesia.We connected to the anesthesia machine ventilation after the success of tracheal intubation(male: ID7.5;female: ID7.0).All patients underwent radial artery and laternal jugular vein puncture and catheterization before induction of anesthesia to detect invas ive arterial blood pressure and central venous pressure(CVP).Pressure-controlled ventilation with 5 cm H2 O of positive end-expiratory pressure and a tidal volume of 6 to 8 ml/kg was applied during pneumoperitoneum.The arterial and central venous blood gas,respiratory mechanics and hemodynamics were measured and the intra-pulmonary shunt fraction and dead space fraction were calculated at 4 time points:10 minutes after induction of anesthesia,30 minutes after establishing the pneumoperitoneum and changing the posture,30 minutes after switching the I:E ratio,10 minutes after the closure of pneumoperitoneum.Simultaneously,interleukin 6 was detected using quantitative sandwich enzyme immunoassay kits by extracting 5ml venous blood at the following two time points: 10 minutes after induction of anesthesia,30 minutes after establishing the pneumoperitoneum and changing the posture.Results: During the pneumoperitoneum,compared with the traditional 1:2 I:E ratio,peak airway pressure and physiologic dead space were decreased in the 1:1 I:E ratio group.Arterial oxygen tens ion and dynamic compliance were higher in the 1:1 group.However,Pa CO2?Ppeak?Pmean?Qs/Qt and hemodynamic variables had no differences during the pneumoperitoneum regardless of the ventilatory mode we used.Furthermore,the level of IL-6 was significantly reduced.Conclusions: Compared with the traditional 1:2 I:E ratio,pressure-controlled ventilation with a 1:1 I:E ventilation ratio decreased peak airway pressure and physiologic dead space in elderly patients undergoing radical resection of laparoscopic colorectal cancer.It increased Pa O2,improved lung dynamic compliance,reduced the release of inflammatory factor IL-6,reduced perioperative inflammatory response without significant hemodynamic changes.