血氣分析（10版內(nèi)科學）

Items191-194

YouhavebeenassignedtoreviewtheECGsforthegroupthismonth.Many

ofthepatientshaverenalproblemsand/orhypertension.Foreachelec-

trolyteabnormalitybelow,selecttheelectrocardiographicfindingwith

whichitismostcommonlyassociated.

a.NoknownelectrocardiographicabnoiTnalities

b.ProlongedQTinlerval

c.ShortQTinterval

d.WidenedQRScomplex

e.ProminentUwaves

191.Hypokalemia(SELECT1ECGFINDING)

192.Hyperkalemia(SELECT1ECGFINDING)

193.Hypocalcemia(SELECT1ECGFINDING)

194.Hyponatremia(SELECT1ECGFINDING)

Items214-216

214.A40-year-oldalcoholicmaleisbeingtreatedfortuberculosis,buthe

hasnotbeencompliantwithhismedications.Hecomplainsofincreasing

weaknessandfatigue.Heappearscohavelostweight,andhisbloodpres-

sureis80/50mmHg.Thereisincreasedpigmentationovertheelbows.

Cardiacexamisnormal.Thenextstepinevaluationshouldbe

a.CBCwithironandiron-bindingcapacity

b.Erythrocytesedimenialionrale

c.Earlymorningserumcortisolandcosyntropinstimulation

d.Bloodcultures

215.Intheadvancedstageofthisdisease,themostlikelyelectrolyte

abnormalitieswillbe

a.LowserumNa+

bLowserumK*

c.LowserumNa+andhighscrumK/

d.LowserumK+

216.Thetreatmentofchoiceforthispatientis

a.Hydrocortisoneonceperday

b.Hydrocortisonetwiceperdayplusfludrocortisone

c.Hydrocortisoneonlyduringperiodsofstress

d.DailyACTH

225.Apatientwithsmallcellcarcinomaofthelungdevelopslethargy.

Serumelectrolylesaredrawnandshowaserumsodiumof118mg/L

Thereisnoevidenceofedema,orthostatichypotension,ordehydration.

Urineisconcentratedwithanosmolalityof320mmol/kg,SerumBUN,

creatinine,andglucosearewithinnormalrange.Whichofthefollowingis

thenextappropriatestep?

a.Normalsalineinfusion

b.Diuresis

c.Fluidresiriction

d.Tetracycline

Items279-280

279.A30-year-oldmaleisbroughttotheemergencyroomfromprison,

whereheworksinthepaintshop.Hehasnopastmedicalhistory.CTscan

oftheheadisnormal.Urinetoxicologyscreenisnegative.Ethanoland

acetaminophenarenotdetectable.Laboratorydataisasfollows:

Na:138meq/I.

K:4.2meq/L

HCO3:5meq/L

Cl:104meq/L

Creatinine:1.0mg/dL

BUN:14mg/dL

Ca:10mg/dL

Arterialbloodgasonroomair:Po296,Pco220,pH7.02

Bloodglucose:90mg/dL

Urinalysis：normal,withoutblood,protein,orcrystals

Physicalexamination:bloodpressure100/60?withnoorthostaticchange

Neurologicalexamination:barelyarousable,nofocalabnormalities,responds

todeeppain

Whaiistheacid-basedisorder?

a.Non-anion-gapmetabolicacidosis

b.Respiratoracidosis

c.Anion-gapmetabolicacidosis

d.Anion-gapmetabolicacidosisplusrespiratory7alkalosis

280.Inthispatient,whichtestwillprovidethekeytocorrectdiagnosis?

a.Serumketones

b.Serumlactate

c.Salicylatelevel

d.Measuredplasmaosmolality

Items281-282

281.A70-year-oldmaleisfoundlethargicathomewilhabloodpressure

of98/60andatemperatureof98.6°EIntheemergencyroom,thefollow-

inglaboratorystudiesareobtained:

Na:138meq/L

K:2.8meq/L

11CO3:10meq/L

Cl:117meq/L

BUN:20mg/dL

Creatinine:1.0mg/dL

Arterialbloodgases:Po280,Pco225,pH7.29

UrinepH:4.5

Whaiistheacid-basedisorder?

a.Non-anion-gapmetabolicacidosis

b.Respiraioryacidosis

c.Anion-gapmetabolicacidosis

d.Non-anion-gapmetabolicacidosisandrespiratoralkalosis

282.Themostlikelycauseofthepatientsdisorderis

a.G1lossduetodiarrhea

b.Proximalrenaltubularacidosis

c.Distalrenaltubularacidosis

d.Disorderoftherenin-angiolensin-aldosleronesystem

Items283-284

283.A68-year-oldfemaleisfoundathomehypotensive(bloodpressure

80/60)andconfused.Shehasihefollowinglaborator)7resultsintheemer-

gencyroom:

Na:130meq/L

K:2.6meq/L

Cl:70meq/L

HCO3：50meq/L

BUN:40mg/dL

Creatinine:1.7mg/dL

Arterialbloodgases:Po262,Pco247,pH7.63

Whichacid-basedisorderispresent?

a.Metabolicalkalosis

b.Respiraioiyacidosis

c.Metabolicalkalosisplusrespiratoryacidosis

d.Respiraioiyalkalosis

284.Whichofthefollowinglaboratorytestsismostusefulindetermining

theetiologyoftheacid-basedisorderofthispatient?

a.Urinesodium0)

b.Urinechloride

c.UrinepH

d.Urinepotassium

Item290-291

290.A63-year-oldmalealcoholicwitha50-pack-yearhistoryofsmoking

presentstotheemergencyroomwithfatigueandconfusion.Physical

examinationrevealsabloodpressureof110/70withnoorthostaticchange.

Heart,lung,andabdominalexaminationarenormalandthereisnopedal

edema.Laboraiorydataisasfollows:

Na:110meq/L

K:3.7meq/I.

Cl:82meq/L

HCO-,：20meq/L

Glucose:100mg/dL

BUN:5mg/dL

Creatinine:0.7mg/dL

Urinalysis:normal

Themostlikelydiagnosisis

a.Volumedepletion

b.Inappropriatesecretionofantidiurelichormone

c.Polydipsia

d.Cirrhosis

291.Whichisthemostusefulfirststepintheassessmentofhyponatremia

inthispatient?

a.Plasmaargininevasopressin

b.Urinesodium

c.Urineosmolality

d.Physicalexamination

292.Apatientwithaserumsodiumof110meq/l.suffersgrandmal

seizures.CTscanoftheheadandlumbarpuncturearenormal.Whatis(he

immediatetreatmentofthehyponatremia?

a.Normalsalineat250mL/h

b.750mLoralfluidrestriction

c.3%salineal30to40mL/hplusfurosemide

d.Demeclocycline

Items293-295

293.A65-year-olddiabeticwithacreatinineof1.6wasstartedonan

angiotensinconvertingenzymeinhibitorforhypertensionandpresentsto

theemergencyroomwithweakness.Hisothermedicationsincludeastatin

forhypercholesterolemia,abetablockerandspironolactoneforcongestive

heartfailure,insulinfordiabetes,andaspirin.Laboraioryexaminations

include:

K:7.2nieq/L

Creatinine:1.8

Glucose:400mg/dL

CPK:400IU/L

Whichisthemostimportantcauseofhyperkalemiainthispatient?

a.Worseningrenalfunction

b.Uncontrolleddiabetes

c.Stalin-inducedrhabdomyolysis

d.Drug-induceddefectsintherenin-angiotensin-aldosteronesystem

295.IfthispatienthasawidenedQRSonECG,thefirstdruggivenis

a.Intravenoussodiumbicarbonate

bIntravenouscalciumgluconate

c.Intravenousinsulin

d.Polystyrenesulfonate(Kayexalate)

Items341-342

341.A58-year-oldScandinavianmalepresentswithshortnessofbreath

andisfoundtohaveanemia.Peripheralbloodsmearshowsmacrocytosis

andhjrpersegmentedpolyps.Thepatientalsohasposturalhypotension.

Skinshowsbothvitiligoandhyperpigmentation.Rombergsignispositive.

Serumsodiumis120meq/L(normalis136to145meq/L)andpotassium

is5.2meq/L(normalis3.5to5.0meq/L).Urinarysodiumisincreased.

Whichofthefollowingiscorrect?

a.Thepatient^sympiomswillbeexplainedonthebasisoffolatedeficiency

b.Only50%ofsuchpatientswillhaveparietalcellantibody

c.ThepatientislikelytohavelowlevelsofvitaminB|2andhighlevelsofintrinsic

faclor

d.ThepatieniislikelytohavelowlevelsofvitaminBl2anddecreasedsecretionof

intrinsicfactor

342.Inadditiontoanemia,thispatientismostlikelytohave

a.Addison?diseaseofautoimmuneetiology

b.Piluilaryinsufficiency

c.Hemochromaiosis

d.InappropriateADHsecretion

Items348-351

Matchtheclinicaldescriptionwiththeparaneoplasticsyndromemostoften

associated\vi【hit

a.Humoralhypercalcemiaofmalignancy

b.HyponatremiaduetoinappropriateADHsecretion

350.A48-year-oldcigarettesmokerwilha4-cmhilarmass;transbronchial

biopsyrevealsasquamouscellcarcinoma(CHOOSE1SYNDROME)

35LA58-year-oldcigarettesmokerwhodevelopsacough,hemoptysis,

anda2-cmperihilardensity;sputumcytologyshowssmall,undifferenti-

atedcells(CHOOSE1SYNDROME)

答案

191-194.Theanswersare191-e,192-d,193-b,194-a.(Braunwald,

15/e,p1269.)Hypoxemiatypicallyincreasesautomaticityofmyocardial

fibers,whichresultsinectopicbeatsorarrhythmias.Electrocardiographyin

hypokalemiarevealsflatteningoftheTwaveandprominentUwaves.Hyper-

kalemiadecreasestherateofspontaneousdiastolicdepolarizationinallpace-

makercells,kalsoresultsinslowingofconduction.Oneoftheearliest

electrocardiographicsignsofhyperkalemiaistheappearanceoftall,peaked

Twaves.Moresevereelevationsoftheserumpotassiumresultinwideningof

theQRScomplex.IlypocalcemiaresultsinprolongationoftheQTinterval.

Lowsenimcalciumlevelsmayalsobeassociatedwithadecreaseinmyocar-

dialcontractility.Atserumsodiumlevelscompatiblewithlife,neither

hyponatremianorh)pematremiaresultsinanycharacteristicelectrocardio-

graphicabnormalities.

214.Theanswerisc.(Braunwald,15/e,pp2098-2099.)Thispauenfs

symptomsofweakness,fatigue,andweightlossincombinationwithsigns

ofhypotensionandextensorh^erpigmentationareallconsistentwith

Addison?disease(adrenalinsufficiency).Tuberculosiscaninvolvethe

adrenalglandsandresultinadrenalinsufficiencyMeasurementofserum

cortisolbaselineandthenstimulationwithACTHwillconfirmtheclinical

suspicion.TheACTHstimulationtestisusedlodeterminetheadrenal

reservecapacityforsteroidproduction.Cortisolresponseismeasured60

minaftercosyniropinisgivenintramuscularlyorintravenously.

215.Theanswerisc.(Braunwald,15/e,pp2098-2099.)Hyponatremiais

duetolossofsodiumintheurine(aldosteronedeficiency)andmovement

ofsodiumintracellularly.Extravascularsodiumlosscauseshypotension.

Hyperkalemiaisduetoaldosteronedeficiency,impairedglomenilarfiltra-

tion,andacidosis.

216.Theanswerisb.(Braunwald,15/etpp2098-2099.)Hydrocortisoneis

themainstayoftreatment,Txvo-thirdsofthedoseistakeninthemorning

andone-thirdatnightinordertoapproachnormaldiurnalvariation.The

recommendeddoseis20to30mg/d.Themineralocorticoidcomponentof

adrenalhormonesalsoneedstobereplaced.Fludrocortisoneisgivenata

dosageof0.05to0.1mg/d.Duringperiodsofiniercurrentstressorillness,

higherdosesofbothglucocorticoidandmineralocorticoidarerequired.

225.Theanswerisc.(Braunwaldt15/e,pp2058-2059.)Thepatient

describedhashyponatremia,normovolemia,andconcentratedurine.

Thesefeaturesaresufficienttomakeadiagnosisofinappropriateanti-

diuretichormonesecretion.InappropriateADHsecretionoccurs,insome

cases,duetoectopicproductionbyneoplastictissue.Treatmentnecessi-

279.Theanswerisc.(Braunwald,15/efp284.)ThepHislow,sothepri-

maryprocessisacidosis.TheserumHCO3hasdecreasedfrom24to5

meq/L,sothisisametabolicacidosis.ThePco2is20mmHg,downfroma

normal40mmHg,anormalcompensation(Pcchdecreasesby1to1.5mgHg

foreach1-meqdecreaseinHCO3).Thenormalaniongap(Na-[Cl+

HCOJ)is8to12meq/L;hereitis29meq/L.Thusthisisananion-gapmeta-

bolicacidosiswilhappropriaterespiratorycompensation.Abriefdifferential

ofanion-gapmetabolicacidosisisasfollows:

Diabeticketoacidosis

Lacticacidosis

Alcoholicketoacidosis

Toxicalcoholingestion(methanol,ethyleneglycol)

Salicylateintoxication

Renalfailure

Non-anion-gapmetabolicacidosisisexcludedbytheaniongapof31.

RespiraloryacidosisisexcludedbythelowPco2-Anion-gapmetabolicaci-

dosisplusrespiratoryalkalosisisexcludedbecausethePco2of20mmHg

isappropriatecompensation,nottruerespiratoryalkalosis.

280.Theanswerisd.(Braunwaldt15/etp287.)Plasmaosmolalityiscal-

culatedasfollows:2xNa4-BUN/2.8+glucose/18+bloodethanol/4.6

(denominatorsareafunctionofmolecularweight).Herethecalculated

osmolalityis288mosni/L(2x138+14/2.8+90/18+0/4.6).Assumea

measuredplasmaosmolalityof320mosm/L.Themeasuredosmolalityof

320mosm/Lminusthecalculatedosmolalityof288mosm/Lis32(nlless

than10),consistentwithalargeosmolargap,dueeithertomethanolor

ethyleneglycol.Inthiscase,methanol,usedinpaintthinners,islikely.Eth-

yleneglycol,usedinantifreeze,isfrequentlyassociatedwkhhypocalcemia,

renalfailure,andctysialluria.Serumketonesshouldbechecked,butdia-

beticketoacidosisisunlikelywithabloodsugarof90mg/dL,andalcoholic

ketoacidosisrarely,ifever,causesacidosisofthisseverity.Serumlactate

shouldbechecked,butinanafebrilepatientwithnormalbloodpressure

lacticacidosisisunlikelytobetheprimarycause.Elevatedsalicylatelevel

causesmixedmetabolicacidosis-respiratoryalkalosiswithanearnormal

pHintheaduk.Inaninfant,severemetabolicacidosismayoccur.

281.Theanswerisa.(Braunwald,15/c,p286.)WithapHof7.29,the

primaryprocessisacidosis.TheHCO3islow(10meq/1.)andtheaniongap

isnormalat11meq/L,andthePco2of29mmHgisappropriaterespirator)^

compensation.Thusthisisanon-anion-gapmetabolicacidosiswithappro-

priaterespiratorycompensation.Abriefdifferentialdiagnosisisasfollows:

GIHCO3lossbelowtheligamentofTreitz

RenalIICO3(proximalrenaltubularacidosis,distalrenaltubularacidosis)

Defectsoftherenin-angiotensin-aldosteroneaxis

Earlychronicrenalfailure

RespiratoryacidosisisnotconsistentwkhPco2of25mmHg.Anion-

gapmetabolicacidosisisnotconsistentwithanormalaniongap.Non-

anion-gapmetabolicacidosisandrespiratoryalkalosisarenotpresent

becausethePco2representsnormalcompensationforacmeacidosis.

282.Theanswerisa.(Braunyvald,15/e,pp287-288.)Non-anion-gap

acidosis,hypokalemia,andlowurinepHareallconsistentwithgastroin-

testinallossduetodiarrhea.Proximalrenaltubularacidosisisaprimary

disorderfoundmainlyinearlychildhood.kmaybeseeninunusualaduk

systemicdiseases,butnotasanacuteacidosis.UrinepHisusuallyhigh.

DistalrenaltubularacidosisisexcludedbyaurinepHoflessthan6.Dis-

ordersoftherenin-angiotensin-aldosteronesystemareacommoncauseof

hyperchloremicacidosisinolderpatients,butdefectsinaldosteronefunc-

tioninvariablycausehyperkalemia,nothypokalemia.

283.Theanswerisa.(Braunwald,15/efpp288-289.)ThepHishighand

theplasmaHCO3ishigh,consistentwithmetabolicalkalosis.Therespira-

lorycompensationislimitedbyhypoxicdrive.UsuallywhenthePco2rises

tothehigh40sorlow50s,hypoxicdriveisstimulatedtomaintainaPO2>

60mgllgasinthepresentcase.Abriefdifferentialdiagnosisisasfollows:

Lowornormalbloodpressure

UpperGIlossabovetheligamentofTreitz

Renalloss(eg,duetodiuretics)

Increasedbloodpressure

Primaryaldosteronism

Cushing?diseaseorsyndrome

Anymineralocorticoidexcess

Miscellaneous

Bantersyndrome

RespiratoracidosiscannotbetheprimaryabnormalitywithhighpH.

Metabolicalkalosisplusrespiratoracidosisisexcludedbecausethe

increasedPco2representsappropriatecompensation,notaprimarydisor-

der.RespiratoryalkalosisisimpossiblewithhighPco2.

284?Theanswerisb.(Braunwald,15/e,p289.)Thispatienthaslow

bloodpressureandmetabolicalkalosis.Therefore,herdisorderisdue

eithertoGIloss(eg,vomiting)ortorenalloss(e.g.,furosemide).Urine

chloridewillbelowintheformerandhighinthelatter(exceptifoffdiuret-

icsfordays).UrinesodiumwillnotdifferentiateGIfromrenallossesandis

likelytobesurprisinglyhighinboth.WithaplasmaHCO3of50,obliga-

loryrenallossofHCO3willoccur,requiringcationloss(eithersodiumor

potassium)tomaintainelectroneutraliiy.UrineHCO3losswillcauseahigh

urinepHwithaplasmaHCO3of50.UrineHCO3lossplushighlevelsof

aldosteroneduetovolumedepletionwillcauseurinarypotassiumloss

despitehypokalemia,

290.Theanswerisb.(Braunwald,15/ctpp274-275.)Inappropriatesecre-

tionofantidiuretichormoneisadiagnosisofexclusion,butachestx-ray

mightrevealalungmass.Thissyndromemaybeidiopathic,associated\vkh

certainpulmonaryandintracranialpathologies,duetoendocrinedisorders

(e.g.,hypothyroidism),ordrug-induced(e.g.,manypsychotropicagents).

Significantvolumedepletionisexcludedbytheabsenceoforthostatic

hypotension.Asonecanexcrete20%oftheglomerularfiltrationrate,one

wouldhavetoingestmorethan20L/daytobecomehyponatremic.Cirrho-

sisisveryunlikelyintheabsenceofascitesandedema.

291.Theanswerisd.(Braunwild,15/e,pp274-275.)Physicalexamina-

tionisthemostimportantfirststep.Hyponatremia(ellsusaboutthetonic-

ityofplasma,notabouttotalbodysodium.Hyponatremicpatientsmay

havelowtotalbodysodium(e.g.,volumedepletion),whichwillcause

orthostatichypotension;hightotalbodysodium(eg.,congestiveheartfail-

ure,cirrhosis,nephroticsyndrome),whichwillcauseedema,ornormal

bodysodium(inappropriateantidiuretichormonesecretion)withneither

oftheabove.Plasmaargininevasopressinwillbehighinallhyponatremic

stalesexcepttherarecaseofpolydipsia.Urinesodiumcanbehighorlow

withvolumedepletion(diarrheaversusdiuretics)andhighorlowwith

inappropriateantidiuretichormonesecretion(refleccingdietaryintake).

Urineosmolalityishighinallthesestatesduetohighargininevasopressin

levels.

292.Theanswerisc.(Braunwald,15/etp276.)Seizuresduetosevere

hyponatremiaareamedicalemergency.Hypertonicsalineatthisslowrate

plusfurosemidetocreateanisotonicurinewillcorrectthehyponairemiaal

%to1meq/h.Overlyrapidcorrectioncanleadcoirreversiblecentralpon-

tinemyelinolysis.Dependingontheurineosmolalitynormalsalineat

250mL/hmayfailtohelpandmaypotentiallyaggravatethesituation.

Oralfluidrestrictionto750mLisappropriate,butwillnothelpacutely.

Demeclocyclineinducesnephrogenicdiabetesinsipidusandmayplaya

roleinchronictherapy.Avoiditin山esettingofliverdisease,asdeathfrom

liverfailurehasoccurred.

293.Theanswerisd.(Braunwald,15/e,pp281-282.)Thesyndromeof

hyporeninemichypoaldosteronismoccursinolderdiabetics,particularly

maleswithcongestiveheartfailure.Thesyndromeoftenpresentswhen

aggravatingdrugsareadded.Betablockersimpairreninsecretion,convert-

ingenzymeinhibitorsdecreasealdosteronelevels,andspironolactone

competesforthealdosteronereceptor.Combinedwithdiabetesandmild

renalinsufficiency,theresultmaybesignificanthyperkalemia.Themoder-

ateincreaseincreatinineisunlikelytocauseseverehyperkalemia.The

hypertonicityduetohyperglycemiacouldaggravatehyperkalemia、buta

bloodglucoseof400mg/dLshouldnotcauseseverehyperkalemia.Slatin

drugsmaycausemuscleinjuryandrhabdomyolysis,butaCPKof400IU/1.

isamodestelevationandwouldnoicauseseverehyperkalemia.

294.Theanswerisc.(Braiifwald,15/etp282.)Hyperkalemiainducesa

seriesofECGchangesprogressingfrompeakedTwavestoawidenedQRS

toasystole.Theevidenceof