The Impact Of Small Tidal Volume Ventilation On Eurosurgical Patients' Serum SP-A And TNF-α

Objective:General anesthesia deteriorates gas exchange peri- and post-operatively,which causes hypoxemia in lung-healthy patients. Mechanical ventilation should keep homeostasis,avoid ventilator-induced lung injury and lessen ventilation/perfusion mismatch caused by general anesthesia.In order to avoid ventilator induced lung injury, lung protective strategies by using a lower tidal volume and higher respiratory frequency are now advocated.We observed the effects of lower tidal-volume ventilation on respiratory mechanics and blood gas analysis parameters in the patients during intracranial surgery,and its clinical appliance was evaluated.Methods:80 adult patients(aged 18-60,ASAâ… -â…¡,cardiac functionâ… -â…¡) who undergoing intracranial surgery were randomly distributed into two groups according to different tidal volumes(group TV with a conventional tidal volume of 12 ml/Kg,group LV with a low tidal volume of 7 ml/Kg).P_ETCO₂ was kept on 35±5mmHg by adjusting respiratory frequency for an equivalent ventilation in the two groups,the ratio of inspiratory to expiratory time(I/E) on 1:2,oxygen flow on 2L/min,and FiO₂ on 100%.Blood gas analysis were measured and HR,MAP were drawn before operation(T0),30min(T1),120min (T2),240min(T3)after intubation and 8 hour(T4)。respiratory mechanical parameters were drawn at different time points including T1.T2 and T3.Blood samples were colleted from peripheral vein at different time points including T0 and 48 hours after operation。The serums were stored by refrigerator under -20℃and were used for measuring TNF-αand SP-A concentrationResult:Ppeak,Pplat,Pmean,and lung compliance(Cst) were significantly higher in group TV than those in group LV;Rf were significantly lower in group TV than those in group LV;PaO₂,Ri,P(A-a)O₂ and PaCO₂ had no significant differences between the two groups;Cst during operation decreased progressively in both groups,as PaCO₂ in group TV rose gradually。At 8h after operation,there were no significant differences in blood gas analysis parameters between group TV and LV(P＜0.05),they recovered to the level before general anesthesia.There were no significant differences in TNF-αbetween group TV and LV before general anesthesia。TNF-αin the two groups was increased after OLV,But group TV was higher than group LV.there were no significant differences in SP-A between group TV and LV before general anesthesia.SP-A in TV group was increased obviously after OLV。Compared with group LV,there was significant increase in group TV. Conclusion1,The small tidal volume(7ml/kg) mechanical ventilation of serum SP-A,TNF-αrelease of reduced protective effect on lung.2,The small tidal volume(7ml/kg) mechanical ventilation to maintain a lower peak airway pressure,plateau pressure may be one of the mechanisms of lung protection.