Effect Of Lung Protective Ventilation Strategy On Postoperative Oxygenation In Patients With Oral Cancer

Objective:To investigate the effect of LPVS on postoperative oxygenation in patients with oral cancer.Methods:A total of 90 cases of oral cancer were selected。Inclusion criteria:aged 40～70 years,treated oral cancer surgery under general anesthesia and operated time over 6 h,with postoperative pulmonary complications risk score greater than or equal to 26 points,ASAI～Ⅱlevel and cardiac function class I～Ⅱ（NYHA classification）,no serious cardiopulmonary disease,normal liver and kidney function,electrolyte,electrocardiogram,chest X-ray and lung function were not significantly abnormal.All patients and their families included in the study were approved by the ethics committee and signed the informed consent.Exclusion criteria:received mechanical ventilation treatment and existed acute infection and sepsis within 2 weeks before surgery;Body mass index greater than or equal to 30 kg/m²;patients with severe cardiopulmonary diseases before surgery,such as bronchial asthma,chronic obstructive pulmonary disease,pulmonary bullae,coronary heart disease,etc.There were chest surgery history,progressive neuromuscular disease,Allergic to narcotic drugs,Psychoneurotic and ventilator-assisted ventilation requiring prolonged ventilation after operation.The patients were divided into three groups（n=30）by the random number table method:Conventional tidal volume（VT=10 ml/kg）in group A,the small tidal volume and low PEEP（VT=6 ml/kg+PEEP=5 cm H₂O）in group B and the small tidal volume,low PEEP and recruitment manoeuvres in group C（VT=6 ml/kg+PEEP=5 cm H₂O+RMs）,recruitment manoeuvres were manually ventilated every hour,and the airway pressure was maintained at 30 cm H₂O for 30 s.All patients with oral cancer were mechanically ventilated with IPPV,I:E for 1:2,inhaled oxygen concentration of 60%,and the target P_ETCO₂was maintained at 35-45 mm Hg by adjusting the respiratory rate for 10-18 times per minute.Calculated by PBW（kg）:male:50+0.91×（height-152.4）;Female:45.5+0.91×（height-152.4）.All patients with oral cancer were given total intravenous anesthesia.Phenobarbital sodium 0.1 g and atropine 0.5 mg were intramuscularly injected30 minutes before anesthesia.After entering the room,the venous access of lower extremity was opened and ECG,HR,BP,Sp O₂,T and P_ETCO₂were monitored.Induction of anesthesia:midazolam 0.1 mg/kg,etomidate 0.3 mg/kg,sufentanil target-controlled infusion 0.2-0.3 ng/ml,cis-atracurium 0.15-0.2mg/kg.Under visual laryngoscope,6.0 or 6.5 nasal abnormal tracheal tube was inserted through rhinoplasty and connected with anesthesia machine to perform mechanical ventilation according to the above ventilation mode.Fiberoptic bronchoscope intubation was used in patients with difficult airway.Anesthesia maintenance:intravenous target-controlled infusion of propofol 2.5-3.5 ug/ml and sufentanil 0.2-0.3 ng/ml,continuous infusion of cis-atracurium 0.1 mg/k×h for maintain muscle relaxation.After general anesthesia,dorsalis pedis artery puncture and catheterization were performed to continuously monitor the invasive arterial blood pressure,and femoral vein puncture and catheterization were performed for fluid replenishment or blood transfusion.The blood pressure was maintained within the baseline level（+20%）during the operation.If the mean arterial pressure was below 65 mm Hg,dopamine 2-4 mg was injected intravenously to correct it.If the heart rate is lower than 55 beats per minute,atropine 0.25-0.5 mg intravenous injection should be corrected.The intraoperative rehydration crystal was mainly sodium lactate ringer injection,the colloid was mainly hydroxyethyl starch,and the gel was injected according to the crystal gel ratio of 3:1.If the hemoglobin was lower than 70 g/d L,the without white cells erythrocytes were infused.Tracheotomy was performed after the operation and the patients which was fully awake were sent to the intensive care unit for nursing observation.Mean arterial pressure（MAP）,heart rate（HR）,blood oxygen saturation（Sp O₂）and body temperature（T）were recorded before operation（T1）,30 minutes after mechanical ventilation（T2）,2 hours after mechanical ventilation（T3）,the end of surgery（T4）,the first day after surgery（T5）and the third day after surgery（T6）.Peak airway pressure（Ppeak）and Compliance of lung（CL=VT/Ppeak-PEEP）were recorded at T2,T3 and T4.Arterial blood was drawn at T1,T3 to T6 for blood gas analysis,arterial partial pressure of oxygen（Pa O₂）,Arterial Partial Pressure of Carbon Dioxide（Pa CO₂）,pulmonary alveolar partial pressure difference[P（A-a）DO₂]and oxygenation index（OI）were recorded.White blood cell count（WBC）and C-reactive protein（CRP）were measured by venous blood sampling at T1,T5and T6 and CPIS was calculated at the same time.The operation time,hospitalization time,the time of removal of the air-cut catheter and complications within 72 hours were recorded.Results:There was no significant difference in gender,age,operation time,hospital stay postoperative and time of removal of the air-cut catheter among the three groups（P>0.05）.MAP,HR,Sp O₂and T were not statistically significant（P>0.05）.The Ppeak values at T2,T3 and T4 in three groups showed an upward with the duration of mechanical ventilation and group A was significantly higher than group B and C.At the same time,CL values decreased gradually with the progress of surgery and the decrease in group A at T4 was more significant than that in group B and C（P<0.05）.There was no statistically significant difference in Pa O₂,Pa CO₂,P（A-a）DO₂and OI among three groups at T1（P>0.05）;P（A-a）DO₂and Pa O₂in three groups at T3,T4,T5 and T6 was significantly higher than that in T1,but P（A-a）DO₂at T5 and T6 time in group B,C was significantly lower than that in group A（P<0.05）.At T3,T4 and T5,OI in three groups was higher than that in T1,but OI in group B and C was higher than that in group A（P<0.05）;between group B and group C in Ppeak,CL,P（A-a）DO₂,Pa O₂and OI were compared not statistically significant difference.There was no significant difference of Pa CO₂in the 3 groups at T1,T3,T4,T5 and T6 time（P>0.05）.WBC,CRP and CPIS scores at T5 and T6were significantly higher in the three groups（P<0.05）,while CRP and CPIS scores at T5 and T6 in group B and C were lower than those in group A（P<0.05）.There was no significant difference among the three groups of WBC（P>0.05）.No serious adverse reactions occurred during the operation in the three groups and there was no statistically significant difference in the incidence of adverse events among the three groups（P>0.05）.The incidence of complications in group B and C within 72 hours after operation was significantly lower than that in group A（P<0.05）.Conlusion:All three ventilation modes can maintain good oxygenation and stable circulation function in oral cancer whose mechanical ventilation lasts more than 6 hours.Compared with conventional tidal volume ventilation mode,however,small tidal volume combined with PEEP and small tidal volume combined with PEEP and pulmonary reexpansion ventilation mode can help patients recover their pulmonary oxygenation function in the early stage after operation,which improve the early oxygenation function after operation,increase the effective alveolar ventilation volume,and alleviate perioperative lung injury to a certain extent.It is a safe and feasible ventilation mode for oral cancer patients during perioperative period.