Protective Effect Of N-acetylcysteine On Lung Injury Induced By Cardiac Pulmonary Bypass

Objective： To study the protective effect and relative mechanism ofN-acetylcysteine (NAC) to CPB-induced lung injury through observing theeffectiveness of NAC on various indicators of SP-A, TNF-α IL-6et.al in patientssuffering cardiac pulmonary bypass.Our aim is to provide basic evidence andprevention measures for clinic treatment,to reduce the rate of pulmonary dysfunctionand accompanying complication induced by CPB.Methods：Forty ASAⅡor Ⅲ patients undergoing cardiac valve replaeememunder CPB were randomly assigned to one of2groups(n=20each)： controlgroup(group C)and NAC group．NAC Group (ten patients) received100mg/kg NACintravenously for before CPB and40mg/kg until the operation is stopped,while incontrol group normal saline was used instead of NAC.Mechanical ventilationparameters,pulmonary surfactant-related protein(SP-A) and cytokines were evaluatedafter induction of anesthesia, sternotomy,thirty minites after release of the aorticcross-clamp, sternalclosure,5h after operation,24h after operation,48h after operation.Results：1. The gender, age, height, weight, aorta blocking time, cpb time andhospitalization time in two groups of patients were no statistically significant difference.Postoperative time of mechanical ventilation and ICU time in the NAC group wasstatistically and significantly lower than the control group.(P<0.05).2.The respiratory index (RI) and alveolar-changes in arterial oxygen partialpressure difference (A-aDO2) of two groups are consistent. The RI and A-aDO2aftercompletion of the closed chest (T3),5hours (T4) and postoperative24hours (T5) inNAC group are significantly reduced, the difference was statistically significant(P<0.05).3.The oxygenation index (T3) after finish closed thoracic operation, postoperative5 hours (T4) and24hours after surgery (T5), especially after5hours (T4), peak(P<0.05)are increased significantly (P<0.05) in NAC group. The airway resistance in thecompletion of the closed chest (T3) and five hours after surgery (T4) in NAC group wassignificantly lower than group C (P<0.05).4. Plasma SP–A, TNF alpha, IL-6and SOD concentration after anesthesiainduction (T0), before CPB and after thoracotomy (T1) are not significant in twogroups(P>0.05). SP-A, TNF alpha and IL-6concentrations in aorta open30min (T2),completion of the closed chest (T3), five hours after surgery (T4) and24hours aftersurgery (T5) in NAC group are significantly lower than C group (P<0.05);but SODconcentration in T2~T5are obviously and statistically higher than C group (P<0.05).Conclusion：NAC has the role of lung protection and could reduce the lung injuryinduced by CPB, whose mechanism may be associated with the alleviation of oxidativestress and inflammation reaction.