The Effect Of Protective Lung Ventilation On Hemodynamics And Respiratory Mechanics In Different Position During Orthopaedic Surgery

Objective:To analysis the effect of two ventilator modes on respiratory mechanics and hemodynamics in different position during orthopaedic surgery,provide reliable reference for its safety application in clinical practice.Method:200 cases(ASA ? or ?)for elective spinal or lower limb surgery with general anesthesia were randomly selected in this study,they were randomly divided into 4 groups(n=50):A group(protective lung ventilation:VT=6 ml/kg,RR=16 beat/min,PEEP=5 cmH2O)and B group(conventional lung ventilation:VT=8-12 ml/kg,RR=12 beat/min,PEEP=0 cmH2O),and A group was devided into A1(prone position)and A2(supine position),B group was devided into B1(prone position)and B2(supine position).The hemodynamic indexes including mean arterial pressure(MAP),heart rate(HR),cardiac index(Cl),stroke volume(SV),central venous pressure(CVP),systemic vascular resistance index(SVRI)were collected at the following time points:TO(before anesthesia induction),T1(5 min after intubation),T2(15 min after the beginning of operation),T3(60 min after the beginning of operation)and T4(15 min after extubation).The respiratory mechanics indexes including mean airway pressure(Pmean),plateau pressure(Pplat),peak airway pressure(Ppeak)and pulmonary compliance(Compl)were collected at T1,T2 and T3.The arterial partial pressure of oxygen(PaO2),arterial partial pressure of carbon dioxide(PaCO2)and alveolar-arterial oxygen tension difference(A-aDO2)were also collected from TO to T4.Result:1.Hemodynamic results:Compare with T0 in A1 and B1 groups,there were significant decrease of MAP(P<0.05)and increase of HR(P<0.05)at T2;but SV was decreasing at T2 and T3(P<0.05).CVP of B1 group was decreasing of at T2 and T3(P<0.05).At T2 and T3,CVP was higher in A1 group than B1 group(P<0.05),and lower in B1 group than B2 group(P<0.05),and SV was lower in A1 group than A2 group(P<0.05).Both in A2 group and B2 group,every variable was not obvious change at each time point(P>0.05).2.Respiratory mechanics results:Compare with Tl,both Ppeak and Pplat increased significantly at T2 and T3 in Al,A2 and B1 groups(P<0.05),and a decrease of Comp1 at T2 and T3 in A1 and B1 groups(P<0.05).Ppeak and Pplat in A2 group were higher than B2 group(P<0.05),and also higher in B1 group than A1 group at T2 and T3(P<0.05).3.Blood gas analysis results:PaCO2 was lower at TO than T2,T3 and T4 in A2 group(P<0.05),and higher in A2 group than B2 group at T2 and T3(P<0.05).PaO2 was apparently higher at T4 than TO in A1 group(P<0.05)and higher in A1 group than B1 group at T4(P<0.05).A-aDO2 was significantly lower at T4 than TO in A1 group(P<0.01)and lower in A1 group than B1 group at T4(P<0.01).Conclusion:During elective orthopaedic surgery with general anesthesia,the protective lung ventilation strategy(low tidal volume:6 ml/kg with PEEP 5 cmH2O)was suitable for the patients without previous lung injury in prone position.The protective lung ventilation strategy had slightly adverse impact on hemodynamics,and it can maintain the respiratory function during operation and oxygenated function after operation,respectively,and reduce the incidence of hypoxemia.It's worth to generalize in clinical practice.