Effect Of Dexmedetomidine On Oxygenation And Respiratory Mechanics Of Patients During One-lung Ventilation

Background:One lung ventilation（OLV）refers to the method of using one lung for ventilation during the operation,which makes the lungs on both sides independent and provides the surgeon with a clear view of the operation.In addition to bringing convenience to surgery,OLV also adversely affects the physiology of patients^[1].During OLV,arteriovenous blood doping,ventilatory blood flow ratio（V/Q）imbalance,and intrapulmonary shunt（Qs/Qt）increase affect the body’s oxygenation^[2].In OLV,the ventilated lung has to withstand a larger ventilation volume.Excessive tidal volume will cause the body’s lung compliance to decrease and airway pressure to rise,leading to lung injury^[3].Dexmedetomidine（DEX）is a highly selectiveα₂receptor agonist commonly used in operating rooms and intensive care units.It has sedation,hypnosis,sympathetic inhibition,reduction of oxidative stress,and reduction of anesthetics and opioids The role of drug use^[4].Studies have found that DEX has a protective effect on the ischemia and hypoxia damage of organs,and has a lung protective effect in the OLV lung model^[5-7].This study intends to explore the effects of DEX on patients’oxygenation and respiratory mechanics during OLV,so as to provide references for clinically reducing oxygenation decline during video-assisted thoracic surgery（VATS）and reducing postoperative complications.Objective:To explore the effect of dexmedetomidine on oxygenation and re spiratory mechanics of patients during one-lung ventilation.Methods:From October 2019 to October 2020,50 patients who underwent pulmonary wedge resection under VATS were selected,aged 40-65 years,BMI 18-26kg·m^-2,ASA classification I or II.The patients were divided into 2 groups by the random number table method:DEX group（dexmedetomidine group）and NS group（normal saline group）.In the DEX group,patients were infused with 1.0ug·kg^-1DEX at a constant rate within 10 minutes after opening the intravenous channel,and then maintained at a rate of 0.5ug·kg^-1·h^-1until the end of OLV.Patients in the NS group were pumped with the same amount of normal saline.The age,gender,BMI index and ASA classification of the patients were recorded before the operation.During the operation,the patient’s surgical site（left and right）,OLV time,blood loss,fluid infusion,and urine output were recorded.Before induction of anesthesia（T₁）,one-lung ventilation for 30 minutes（T₂）,one-lung ventilation for 2 hours（T₃）,and the end of surgery（T₄）,1ml of arterial blood and central venous blood were collected for blood gas analysis,and oxygenation function indicators including P_（A-a）DO₂,OI and Qs/Qt..OI and Qs/Qt.Respiratory mechanics index data collected at T₂,T₃,and T₄include Ppeak,Pplat and Cydn.Central venous blood samples were taken at T₁and T₂,and the serum NO concentration was determined by the nitrate reductase method.Observe whether the patient has pulmonary complications（PPCs）within 5 days after surgery.The clinical pulmonary infection score（CPIS）values were collected after surgery.The number of days from surgery to discharge from the hospital was recorded.Results:1.There was no significant difference in age,gender,BMI index and ASA classification results between the two groups of patients（P>0.05）.2.There was no statistically significant difference in the surgical site,OLV time,blood loss,fluid infusion,and urine output between the two groups of patients（P>0.05）.3.At T₁,there was no statistically significant difference in P_（A-a）DO₂,OI,Qs/Qt between the two groups of patients（P>0.05）.At T₂,T₃,and T₄,P_（A-a）DO₂,OI,and Qs/Qt in the DEX group were better than those in the NS group,and the difference was statistically significant（P<0.05）.4.Ppeak and Pplat of DEX group were lower than those of NS group at T₂,T₃,and T₄,and Cdyn was higher than that of NS group,the difference was statistically significant（P<0.05）.5.Compared with T₁,the serum NO concentration of the two groups was significantly increased at T₂,and the difference was statistically significant（P<0.05）.At T₂,the serum NO concentration of DEX group was significantly higher than that in the NS group,and the difference was statistically significant（P<0.05）.6.There was no pulmonary complications in the DEX group,and there was one atelectasis in the NS group.There was no statistically significant difference between the two groups of data（P>0.05）.The CPIS scores of the two groups were compared,and the DEX group was lower than the NS group,and the difference was statistically significant（P<0.05）.There was no statistically significant difference between the two groups of patients in the days after operation to discharge from the hospital（P>0.05）.Conclusion:1.Dexmedetomidine can enhance the hypoxic pulmonary vasoconstriction effect during one-lung ventilation,reduce intrapulmonary shunt,reduce the occurrence of hypoxemia,and have lung protection.2.Dexmedetomidine reduces airway pressure during one-lung ventilation and improves lung dynamic compliance.