Effects Of Cervical And Thoracic Sympathetic Block On Pulmonary Shunt And Oxygenation In Single Lung Ventilation

BackgroundSingle lung ventilation（OLV）plays an important role in various thoracic surgeries.Hypoxemia occurring in OLV is a limitation in surgery.During OLV,the blood flowing through the unventilated lung returns to the left heart without oxygenation,resulting in decreased venous blood mixture and decreased arterial oxygen partial pressure（Pa O₂）.Although the hypoxic pulmonary vasoconstriction effect（HPV）,as a protective mechanism,can redistribute blood and weaken the pulmonary shunt,some patients can still have significant hypoxemia.As a mature technology,cerothoracic sympathetic block can regulate autonomic nerve,endocrine and other systems,and play a positive role in the stability of the internal environment of the body.ObjectivesBy observing the effect of cervical and thoracic sympathetic block on the shunt oxygenation index of single pulmonary ventilation,explore the protective effect of cervical and thoracic sympathetic block in single pulmonary ventilation and provide new ideas for clinical treatment.MethodsSixty adult male rats,80–100 days old and body weight（350±20）g,were selected.After basal anesthesia they were randomly divided into four groups:cervical sympathetic block（SGB group）,thoracic sympathetic block（TGB group）,cervical and thoracic sympathetic block（SGB+TSB group）,control group.Then administered with a tracheostomy,an endotracheal tube inserted to control breathing,and the tube was subsequently inserted too deep into the right bronchus for single lung ventilation.Monitor vital signs（heart rate,blood pressure,pulse oxygen saturation）during anesthesia.Arterial blood and mixed venous blood samples were taken for blood gas measurement after basic anesthesia（T₀）,both lungs for 15min（T₁）,15min（T₂）,30min（T₃）,60min（T₄）,120min（T₅）,and 30min（T₆）followed by respiratory index（RI）,oxygenation index（OI）,and intra-pulmonary flow（Qs/Qt%）.Results1.Successfully established the rat neck and sympathetic block and thoracic sympathetic block model;2.Observe the hemodynamic changes in the four groups at different time points of the four groups,the heart rate changes in the four groups were less different,but HR between SGB,TGB,SGB and TGB and MAP,but there was no significant difference between the four groups,not significant（P>0.05）;3.The four groups of rats significantly increased Qs/Qt%during single lung ventilation compared with double lung ventilation,RI compared with single lung ventilation,and OI compared with single lung ventilation（P<0.05）.There were no significant differences in HR and MAP between SGB,SGB,TGB and TGB rats and control groups;The RI in the SGB and SGB+TGB groups in the T₀–T₆time period was overall lower than that in the control group（P<0.05）;No overall difference between OI between SGB,TGB,SGB+TGB and control;The Qs/Qt%of the SGB,TGB and SGB+TGB groups were compared with the control group during the T₀-T₆period,lower than the control group（P<0.05）。ConclusionCervical and thoracic sympathetic nerve block does not produce an inhibitory effect on the intrapulmonary shunt and oxygenation after single lung ventilation,and can improve the intrapulmonary shunt and oxygenation index after single lung ventilation.It can improve hypoxemia during single lung ventilation,and can provide some theoretical reference for patients with single lung ventilation in chest surgery.