严重ARDS的治疗策略

严重ARDS的治疗策略成都军区总医院肖贞良什么是ARDS?中华医学会重症医学分会。急性肺损伤/急性呼吸窘迫综合征诊断和治疗指南(2006)。ChinCritCareMed,Dec2006,Vol.18,No112ALI/ARDS是在严重感染、休克、创伤及烧伤等非心源性疾病过程中,肺毛细血管内皮细胞和肺泡上皮细胞损伤造成弥漫性肺间质及肺泡水肿,导致的急性低氧性呼吸功能不全或衰竭。以肺容积减少、肺顺应性降低、严重的通气/血流比例失调为病理生理特征,临床表现为进行性低氧血症和呼吸窘迫,肺部影像学表现为非均一性的渗出性病变。ARDS的关注要点不是一个病，而是一个综合征。可以由一个原发病或诱因导致，也可以是多个诱因共同或序贯作用的结果。ARDS的本质是SIRS，是SIRS的严重阶段；ARDS是MODS或MOF在肺部的表现。“小肺”通气和严重的顽固性低氧血症是其最重要的特征。ARDS的预防远比治疗更有意义.辅助治疗：维持、维护肺脏功能，为原发病的治疗赢得时间。ARDS的诊断标准目前仍广泛沿用1994年欧美联席会议提出的诊断标准:①急性起病;②氧合指数(PaO2/FiO2)≤200mmHg〔1mmHg=0.133kPa,不管呼气末正压(PEEP)水平〕;③正位X线胸片显示双肺均有斑片状阴影;④肺动脉嵌顿压≤18mmHg,或无左心房压力增高的临床证据。如PaO2/FiO2≤300mmHg且满足上述其他标准,可诊断ALI。ARDS的基本治疗策略压力控制通气气道峰压＜35cmH2O,平台压＜30cmH2O小潮气量：4-6ml/kgPEEP8-20cmH2O允许性高碳酸血症(Permissivehypercapnia)严重ARDS的定义当ARDS患者保护性肺通气策略失败,出现顽固性低氧血症和严重酸中毒,肺损伤评分≥3分时,可以认为患者存在严重ARDS,应考虑挽救性治疗措施(Rescuetherapies).CritCareMed2010Vol.38,No.8严重ARDS的定义肺损伤评分0分1分2分3分4分PaO2/FiO2≥300225-299175-224100-174＜100胸片实变无1个项限2个项限3个项限4个项限PEEP≤56-89-1112-14≥15顺应性≥8060-7940-5920-39≤19＊肺损伤评分为以上所有项目评分之和CritCareMed2010Vol.38,No.8严重ARDS的治疗策略-六步法肺复张和高PEEP俯卧位通气(PPV)高频振荡通气(HFOV)一氧化氮吸入(inhaledNO)糖皮质激素glucocorticoid)体外生命支持(ECLS)CritCareMed2010Vol.38,No.8六步法之一:肺复张和高PEEP原理：RecruitmentManeuvers(复张手法）和高PEEP可以使陷闭和实变的部分或全部肺泡恢复通气,从而改善氧合,减少反复开放和关闭肺泡导致的肺损伤.风险：肺泡液清除率下降、VALI和血流动力学障碍。临床实施：RM结合高PEEP或单纯高PEEP，应考虑仅应用于危及生命的严重ARDS早期、有低氧血症且平台压30＜cmH2O者。休克、气胸或局限性病变的患者不建议使用使用RM。实施前需要充分容量复苏和镇静。最佳PEEP设置应高于RM前5-10cmH2O，以维持肺开放。实施6-12小时内应反复评价氧合和顺应性是否得到改善，以决定后续治疗措施。CritCareMed2010Vol.38,No.8常用的RMs控制性肺膨胀(SI)法PEEP递增法压力控制(PCV)法控制性肺膨胀(SI)法如何实施RM?设置FiO2=1.0；等待10分钟；适当镇静；可能需要多次RM。RM必须终止的情况MAP＜60mmHg或下降幅度＞20mmHg；SaPO2＜88%HR＞130or＜60perminute新的心律失常；PEEP递增法PCV法Pins=40cmH2O,40S,20cmH2OPEEP维持方法一方法二AmJRespirCritCareMedVol178.pp1156–1163,2008Rationale:Thereareconflictingdataregardingthesafetyandefficacyofrecruitmentmaneuvers(RMs)inpatientswithacutelunginjury(ALI).Objectives:TosummarizethephysiologiceffectsandadverseeventsinadultpatientswithALIreceivingRMs.Methods:Systematicreviewofcaseseries,observationalstudies,andRCTswithpoolingofstudy-leveldata.MeasurementsandMainResults:Fortystudies(1,185patients)metinclusioncriteria.Oxygenation(31studies;636patients)wassignificantlyincreasedafteranRM(PaO2:106versus193mmHg,P50.001;andPaO2/FIO2ratio:139versus251mmHg,P,0.001).Therewerenopersistent,clinicallysignificantchangesinhemodynamicparametersafteranRM.Ventilatoryparameters(32studies;548patients)werenotsignificantlyalteredbyanRM,exceptforhigherPEEPpost-RM(11versus16cmH2O;P50.02).Hypotension(12%)anddesaturation(9%)werethemostcommonadverseevents(31studies;985patients).Seriousadverseevents(e.g.,barotrauma[1%]andarrhythmias[1%])wereinfrequent.Only10(1%)patientshadtheirRMsterminatedprematurelyduetoadverseevents.Conclusions:AdultpatientswithALIreceivingRMsexperiencedasignificantincreaseinoxygenation,withfewseriousadverseevents.TransienthypotensionanddesaturationduringRMsiscommonbutisself-limitedwithoutseriousshort-termsequelae.GiventheuncertainbenefitoftransientoxygenationimprovementsinpatientswithALIandthelackofinformationontheirinfluenceonclinicaloutcomes,theroutineuseofRMscannotberecommendedordiscouragedatthistime.RMsshouldbeconsideredforuseonanindividualizedbasisinpatientswithALIwhohavelife-threateninghypoxemia.六步法之二：俯卧位通气原理:促进肺膨胀不全区域复张。主要机制是通过减轻外部压力，改善肺通气/血流比例。风险:局部并发症,如面部水肿、结膜出血、压疮；翻身导致管道脱落。临床实施：俯卧位通气持续的时间：建议＞20小时。Introduction:InpatientswithALIand/orARDS,recentrandomisedcontrolledtrials(RCTs)showedaconsistenttrendofmortalityreductionwithproneventilation.Weupdatedameta-analysisonthistopic.Methods:RCTsthatcomparedventilationofadultpatientswithALI/ARDSinproneversussupinepositionwereincludedinthisstudy-levelmeta-analysis.Analysiswasmadebyarandom-effectsmodel.TheeffectsizeonICUmortalitywascomputedintheoverallincludedstudiesandintwosubgroupsofstudies:thosethatincludedallALIorhypoxemicpatients,andthosethatrestrictedinclusiontoonlyARDSpatients.Arelationshipbetweenstudies’effectsizeanddailypronedurationwassoughtwithmeta-regression.Wealsocomputedtheeffectsofpronepositioningonmajoradverseairwaycomplications.Results:SevenRCTs(including1,675adultpts,ofwhom862wereventilatedintheproneposition)wereincluded.ThefourmostrecenttrialsincludedonlyARDSpatients,andalsoappliedthelongestproningdurationsandusedlung-protectiveventilation.Theeffectsofpronepositioningdifferedaccordingtothetypeofstudy.Overall,proneventilationdidnotreduceICUmortality(oddsratio=0.91,95%confidenceinterval=0.75to1.2;P=0.39),butitsignificantlyreducedtheICUmortalityinthefourrecentstudiesthatenrolledonlypatientswithARDS(oddsratio=0.71;95%confidenceinterval=0.5to0.99;P=0.048;numberneededtotreat=11).Metaregressiononallstudiesdisclosedonlyatrendtoexplaineffectvariationbyproneduration(P=0.06).Pronepositioningwasnotassociatedwithastatisticalincreaseinmajorairwaycomplications.Conclusions:LongdurationofventilationinpronepositionsignificantlyreducesICUmortalitywhenonlyARDSpatientsareconsidered.六步法之三：高频振荡通气(HFOV)原理：使用高平均气道压，使肺泡复张并改善氧合；通气靠一个振荡活塞在平均气道压上下建立高频率（180-900次/分）压力循环，产生小潮气量（1-2.5ML/KG).风险：高压，可导致血流动力学恶化和气压伤；深度镇静和肌松影响气道分泌