高中英语Unit5 First aid文章 BLEEDING人教版必修五VIP免费

BLEEDINGBleedingiswhenoneormorebloodvesselsaredamagedandcanbefromarteries,veins,orcapillaries.Theseriousnessofthehaemorrhagedependsonthedepthofthecut,amountofbleeding,timetakentocontrolthebleeding,andtypeofbloodvesselsdamaged.Seeingyourownbloodcanbeashock,andonlookerswatchingthescenemayexperienceshock.Thecaregiverisalsoinpotentialdangerofbecominginfectedbyatransmissibledisease—forexample,HIVorhepatitis.Externalbleedingisalmostalwayseasytoidentify,butinternalbleedingisoftenmoredifficulttodetectandtreat.Anaverageadulthasabout5lofbloodandcansafelylosehalfalitre.Rapidlossoflargervolumesofblood,however,leadstohypovolaemicshockanddeath.Hypovolaemicshockisaclinicalstateinwhichtissueperfusionisinadequateduetoalossofbloodorplasma.Areductioninbloodvolumecausesafallinsystolicbloodpressure,whichtriggersasympatheticcatecholamineresponse.Bloodflowtotheperipheriesisreduced.Anaerobicmetabolismwithlactateproductionoccursintissuesthatareinadequatelyperfusedandthiscangoontoimpairthefunctionofvitalorganssuchasthebrain,heart,andkidneys.用心爱心专心