术中血压的影响因素(双语)

TheFactorsAffectBloodPressureZhixiangZhengBoththeseverityanddurationofintraoperativearterialhypotensionhavebeenidentifiedassignificantriskfactorsforpredictingsurgicalmortality.术中低血压的严重程度和持续时间都已经确定为预测手术死亡率重要的危险因素。Particularlyinelderlypatients,delayedorinadequatecorrectionofhypotensioncomprisesnearly40%ofsubstandardintraoperativecareandiscloselyassociatedwithpostoperativemyocardialischemiaandinfarction尤其对于老年人，延迟纠正低血压或纠正不足约占不合格的术中护理的近40％，并和术后心肌缺血和梗死密切相关。BP=CO×SVRCO=SV×HRAdecreaseinbloodpressurewarrantsanoninvasiveassessmentofcardiacoutputwhetherbyend-tidalCO2,arterialwaveformpulsecontouranalysis,orechocardiography.对于血压下降，可通过是如是否获得呼气末二氧化碳，动脉波形分析，或超声心动图对心输出量进行无创评估。AssumingconstantminuteventilationandnoexogenoussourceofCO2,asuddendropinend-tidalCO2by3-4mmHgreflectsareductionincardiacoutputbyapproximately1L/min/m2.如果分钟通气量恒定而且没有外部来源的二氧化碳，呼气末二氧化碳突然下降3-4mmHg反映心输出量减少大约1L/min/m2。Adecreaseinbloodpressurewithnochangeinend-tidalCO2indicatesaprimaryproblemwithsystemicvascularresistancewhichcanbereadilytreatedwithanalpha-agonistdrug.血压下降而呼末二氧化碳没有变化表示主要的问题是体循环血管阻力下降，这可以通过使用α受体激动药来治疗。Adecreaseinbothbloodpressureandend-tidalCO2indicatesaprimaryproblemwithcardiacoutputwhich,inturn,dependsonheartrateandstrokevolume.血压和呼末二氧化碳均下降表示心输出量的下降，心输出量取决于心率和每搏输出量。Inthehypotensivepatientinnormalsinusrhythmandwithareductioninend-tidalCO2,thenextconsiderationisstrokevolumewhichrepresentsthedifferencebetweenend-diastolicvolumeandend-systolicvolume.在低血压同时有正常的窦性心律的病例中，若出现呼气末二氧化碳减少，则应考虑的是每搏输出量，这代表舒张末期容积和收缩末期容积之间的差异。Whileassessingpreload(end-diastolicvolume),dynamicindicessuchaspulsepressurevariabilityorsystolicpressurevariabilitywithpositivepressureventilationaresensitiveindicators.End-diastolicvolumeisalsoaffectedbyafterloadandcontractility.评估前负荷（舒张末容积）时，动态的指标如脉搏压力变异性或正压通气时收缩压变异性是敏感的指标。舒张末容积也受后负荷和心肌收缩力的影响。Afterloadrepresentsallforcesthatopposeleftventricular(LV)fibershorteningduringejectionandincludesventricularshape,size,wallthickness,intracavitarypressure,aorticimpedance,bloodviscosity,andperipheralresistance.SystemicvascularresistanceisfrequentlyusedasanindicatorofLVafterload后负荷代表所有对抗左心室（LV）纤维缩短的力量，包括心室形状，大小，壁厚，腔内压力，主动脉阻抗，血液粘稠度，外周阻力。体循环阻力常用来代表左室后负荷。Anormalheartisinsensitivetoafterloadduetopreloadsensitivitywhereasafailingheartissensitivetoafterloadduetopreloadinsensitivity.正常心脏对后负荷不敏感对前负荷敏感，而心衰时心脏对后负荷敏感而对前负荷不敏感。Inexercisingindividuals,tachycardiarepresentsamajorcomponentofthesympatheticcardiovascularresponsetoincreasecardiacoutputbynearlyfive-fold.However,inanesthetized,supinepatients,increasingheartrateproducesanegligibleeffectoncardiacoutputduetoalimitationincardiacfilling.在运动中，交感神经兴奋导致心率增加，可使心输出量最大至五倍的增加，然而在麻醉仰卧位的病人，由于在心脏充盈的不足，增加心率对心输出量的影响甚微。Heartrhythmisanimportantcomponentofbloodpressureparticularlyinpatientswithnoncompliantventricleswherethevolumecontributionfromaproperlytimedatrialcontractionmayrepresent25-40%ofend-diastolicvolume.心脏节律是构成血压的一个重要组成部分，特别是在心室率不正常的患者，适当节律的心房收缩量可贡献舒张末期容积的25-40％的患者的血液量。Preloadistheforceorloadactingtostretchventricularmyofibrilsatend-diastole前负荷是在舒张末期，舒张的心室肌原纤维所承受的张力。Preloadrecruitablefunctionreferstotheintrinsicabilityofthehearttoincreasetheforceofcontractionandstrokevolumeatgreaterend-diastolicvolumes.前负荷的适应功能是指，在舒张末期容量增加时，心脏相应的增加心肌收缩力和每搏输出量的能力。谢谢观赏WPSOfficeMakePresentationmuchmorefun@WPS官方微博@kingsoftwps