Intensive Care Unit Syndrome: A Dangerous Misnomer

The terms intensive care unit (ICU) syndrome and ICU psychosis have been used interchangeably to describe a cluster of psychiatric symptoms ... IntensiveCareUnitSyndrome:ADangerousMisnomer|CriticalCareMedicine|JAMAInternalMedicine|JAMANetwork Ourwebsiteusescookiestoenhanceyourexperience.Bycontinuingtouseoursite,orclicking"Continue,"youareagreeingtoourCookiePolicy | Continue [SkiptoNavigation] fulltexticon FullText contentsicon Contents figureicon Figures/Tables multimediaicon Multimedia attachicon SupplementalContent referencesicon References relatedicon Related commentsicon Comments DownloadPDF TopofArticle Abstract Clinicalfeatures Etiologyofdeliriumintheicu Management Conclusions ArticleInformation References ViewLargeDownloadCommonDrugsAssociatedWithIntensiveCareUnitUsageandDelirium 1.Hansell  HN Thebehavioraleffectsofnoiseonman:thepatientwith"intensivecareunitpsychosis.”  HeartLung.1984;1359- 65GoogleScholar2.Ramsey  PW BringingapatientthroughICUpsychosis.  RN.September1986;4942- 45GoogleScholar3.Easton  CMacKenzie  F Sensory-perceptualalterations:deliriumintheintensivecareunit.  HeartLung.1988;17229- 235GoogleScholar4.Nadelson  T Thepsychiatristinthesurgicalintensive-careunit,I:postoperativedelirium.  ArchSurg.1976;111113- 117GoogleScholarCrossref5.Helton  MCGordon  SHNunnery  SL Thecorrelationbetweensleepdeprivationandtheintensivecareunitsyndrome.  HeartLung.1980;9464- 468GoogleScholar6.Kornfeld  DSHeller  SSFrank  KAMoskowitz  R Personalityandpsychologicalfactorsinpostcardiotomydelirium.  ArchGenPsychiatry.1974;31249- 253GoogleScholarCrossref7.Abram  HS Adaptationtoopenheartsurgery:apsychiatricstudyoftheresponsetothethreatofdeath.  AmJPsychiatry.1965;122659- 667GoogleScholar8.Hazan  SJ Psychiatriccomplicationsfollowingcardiacsurgery,I:areviewarticle.  JThoracCardiovascSurg.1966;51307- 319GoogleScholar9.Ballard  KS Identificationofenvironmentalstressorsforpatientsinasurgicalintensivecareunit.  IssuesMentHealthNurs.1981;389- 108GoogleScholarCrossref10.AmericanPsychiatricAssociation, DiagnosticandStatisticalManualofMentalDisorders,FourthEdition Washington,DCAmericanPsychiatricAssociation1994;11.WorldHealthOrganization, TheICD-10ClassificationofBehavioralandMentalDisorders Geneva,SwitzerlandWorldHealthOrganization1992;12.Dyer  CBAshton  CMTeasdale  TA Postoperativedelirium:areviewof80primarydata-collectionstudies.  ArchInternMed.1995;155461- 465GoogleScholarCrossref13.Armstrong  SCCozza  KLWatanabe  KS Themisdiagnosisofdelirium.  Psychosomatics.1997;38433- 439GoogleScholarCrossref14.Gustafson  YBerggren  DBrannstrom  B  etal.  Acuteconfusionalstatesinelderlypatientstreatedforfemoralneckfractures.  JAmGeriatrSoc.1988;36525- 530GoogleScholar15.Francis  JMartin  DKapoor  WN Aprospectivestudyofdeliriuminhospitalizedelderly.  JAMA.1990;2631097- 1101GoogleScholarCrossref16.Saravay  SMLavine  M Psychiatriccomorbidityandlengthofstayinthegeneralhospital:acriticalreviewofoutcomestudies.  Psychosomatics.1994;35233- 252GoogleScholarCrossref17.Bruera  EChadwick  SWeinlick  AMacDonald  N Deliriumandseveresedationinpatientswithterminalcancer.  CancerTreatRep.1987;71787- 788GoogleScholar18.Lipowski  ZJ Deliriumintheelderlypatient.  NEnglJMed.1989;320578- 582GoogleScholarCrossref19.Murray  GB Confusion,deliriumanddementia. Cassem  NHed. MassachusettsGeneralHospitalHandbookofGeneralHospitalPsychiatryStLouis,MoMosby–YearBook1991;89- 120GoogleScholar20.Willner  AERabiner  CJWisoff  BGHartstein  MStruve  FAKlein  DF Analogicalreasoningandpost-operativeoutcome:predictionsforpatientsscheduledforopenheartsurgery.  ArchGenPsychiatry.1976;33255- 259GoogleScholarCrossref21.Quinlan  DMKimball  CPOsborne  F Theexperienceofopen-heartsurgery,IV:assessmentofdisorientationanddysphoriafollowingcardiacsurgery.  ArchGenPsychiatry.1974;31241- 244GoogleScholarCrossref22.Kornfield  DSZinberg  SMalm  J Psychiatriccomplicationsofopenheartsurgery.  NEnglJMed.1965;273287- 292GoogleScholarCrossref23.Hackett  TPCassem  NHWishnie  HA Thecoronarycareunit:anappraisalofitspsychologicalhazards.  NEnglJMed.1968;2791365- 1370GoogleScholarCrossref24.Kleck  HG ICUsyndrome:onset,manifestations,treatment,stressorsandprevention.  CCQ.1984;621- 28GoogleScholar25.Horne  JA Areviewofthebiologicaleffectoftotalsleepdeprivationinman.  BiolPsychol.1978;755- 102GoogleScholarCrossref26.Horne  JAPettitt  AN Highincentiveeffectonvigilanceperformanceduring72hoursoftotalsleepdeprivation.  ActaPhysiol(Amst).1985;58123- 139GoogleScholar27.Pilcher  JJHuffcutt  AI Effectofsleepdeprivationonperformance:ameta-analysis.  Sleep.1996;19318- 326GoogleScholar28.Morris  GOWilliams  HLLubin  A Misperceptionanddisorientationduringsleepdeprivation.  ArchGenPsychiatry.1960;2247- 254GoogleScholarCrossref29.Harrell  RGOthmer  E Postcardiotomyconfusionandsleeploss.  JClinPsychiatry.1987;48445- 446GoogleScholar30.Johns  MWLarge  AAMasterton  JPDudley  AF Sleepanddeliriumafteropenheartsurgery.  BrJSurg.1974;61377- 381GoogleScholarCrossref31.Redding  JSHargest  TSMintsley  SH Hownoisyisintensivecare?  CritCareMed.1977;5275- 276GoogleScholarCrossref32.Bentley  SMurphy  FDudley  H Perceivednoiseinsurgicalwardsandanintensivecarearea:anobjectiveanalysis.  BMJ.1977;21503- 1506GoogleScholarCrossref33.Davison  GCNeale  JM AbnormalPsychology 4thed.NewYork,NYJohnWiley&SonsInc1986;34.Dubin  MDField  HLGastfried  BS Postcardiotomydelirium:areview.  JThoracCardiovascSurg.1979;77586- 594GoogleScholar35.vanderMast  RCRoest  FHJ Deliriumaftercardiacsurgery:acriticalreview.  JPsychosomRes.1996;4113- 30GoogleScholarCrossref36.Cassem  NHHackett  TP Thesettingofintensivecare. Cassem  NHed. MassachusettsGeneralHospitalHandbookofGeneralHospitalPsychiatryStLouis,MoMosby–YearBook1991;373- 400GoogleScholar37.Tesar  GEStern  TA DiagnosisandtreatmentofagitationanddeliriumintheICUpatient. Rippe  JMIrwin  RSFink  MPCerra  FBeds. IntensiveCareMedicineBoston,MassLittleBrown&CoInc1996;2487- 2496GoogleScholar38.AmericanPsychiatricAssociation, PracticeGuidelinefortheTreatmentofPatientsWithDelirium Washington,DCAmericanPsychiatricAssociation1999;39.Britton  ARussell  R Multidisciplinaryteaminterventionsinthemanagementofdeliriuminpatientswithchroniccognitiveimpairment:areviewoftheevidenceofeffectiveness[CochraneReviewonCD-ROM]. Oxford,EnglandCochraneLibrary,UpdateSoftware1998; (issue4) 40.Tess  MM Acuteconfusionalstatesincriticallyillpatients:areview.  JNeurosciNurs.1991;23398- 402GoogleScholarCrossref41.Layne  OLYudofsky  SC Postoperativepsychosisincardiotomypatients.  NEnglJMed.1971;289518- 520GoogleScholarCrossref42.Surman  OSHackett  TPSilverberg  ELBehrendt  DM Usefulnessofpsychiatricinterventionsinpatientsundergoingcardiacsurgery.  ArchGenPsychiatry.1974;30830- 835GoogleScholarCrossref SeeMoreAbout 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ArchInternMed.2000;160(7):906-909.doi:10.1001/archinte.160.7.906 visualabstracticon VisualAbstract editorialcommenticon EditorialComment relatedarticlesicon RelatedArticles authorinterviewicon Interviews multimediaicon Multimedia Abstract Thetermsintensivecareunit(ICU)syndromeandICUpsychosishavebeenusedinterchangeablytodescribeaclusterofpsychiatricsymptomsthatareuniquetotheICUenvironment.ItisoftenpostulatedthataspectsoftheICU,suchassleepdeprivationandsensoryoverloadormonotony,arecausesofthesyndrome.Thisarticlereviewstheempiricalsupportforthesepropositions.WeconcludethatICUsyndromedoesnotdifferfromdeliriumandthatICUsyndromeiscausedexclusivelybyorganicstressorsonthecentralnervoussystem.WearguefurtherthatthetermICUsyndromeisdangerousbecauseitimpedesstandardizedcommunicationandresearchandmayreducethevigilancenecessarytopromptlyinvestigateandreversethemedicalcauseofthedelirium.Directionsforfutureresearcharesuggested. Numerousauthorshavenotedaclusterofpsychiatricsignsandsymptomsthatmayoccurinpatientswhoaretreatedinanintensivecareunit(ICU)orhigh-dependencywardandhavetermedthissyndromeICUpsychosis,1-3postoperativedelirium,4andICUsyndrome5;whenpatientshaveundergoneheartsurgery,ithasbeencalledpostcardiotomydelirium6orcardiacpsychosis.7Frequently,thissyndromeisassumedtobepeculiartoICUs. Theaimsofthisarticlearetoreviewtheetiologyandnatureofthissyndromeandthentodiscusstheimplicationsofthisreviewfornosologyandmanagement.IsthereactuallyapsychiatricsyndromethatisattributabletosomefeatureoftheICUexperience,oristhis"syndrome"mostaccuratelyandmosthelpfullyclassifiedasadelirium?Wearguethatthelatteristrueandthatitispossibleandpreferabletodescribethedisorderusingestablishedmedicalnomenclature.Appropriateclassificationwillhelptodemystifytheconcept,ensurethatcrucialorganiccausesaresoughtandfound,indicateoptimalmanagement,andfacilitatestandardizedresearch. Clinicalfeatures SeveralauthorshavedescribedthefeaturesofICUsyndrome,andwhilethereareinconsistenciesinthewaythesyndromeisdescribed,thesuggestedhallmarksignsareafluctuatinglevelofconsciousness,poororientation,delusionsandhallucinations,andbehavioralanomalies,suchasaggressionorpassivity.1,3,5TheICUsyndrome,asusuallydescribed,hasarapidonsetandistransient,lastingonly24to48hours,8althoughalongeraveragedurationof14.7dayshasbeenreported.9Thesefeaturesareconsistentwiththediagnosisofdelirium.TheremainderofthisarticleisdevotedtodeliriumintheICUsetting,unlessthetermICUsyndromeisspecified. DeliriumisclearlydescribedinboththeDiagnosticandStatisticalManualofMentalDisorders,FourthEdition,10andtheInternationalClassificationofDiseases,10thRevision,11whichrepresentthemajorclassificationsystemsapplyingtopsychiatry.Inboth,deliriumissaidtofeatureadisturbanceofconsciousnessandattention;achangeincognitionorperceptualdisturbances,suchashallucinations;arapidonset;andtheassumptionofanunderlyingmedicalcause. Theaverageincidenceofpostoperativedeliriumhasbeenfoundtobeapproximately40%,12althoughtheincidencemayvaryaccordingtothetypeofICUorhigh-dependencyward.Somestudieshavedemonstratedaconsistentrateofunderdiagnosis,13,14sothatthetrueincidencemayexceed40%.DeliriumintheICUisassociatedwithlongeradmissions15,16andincreasedmortality,15,17althoughthismaybeaconsequenceoftheunderlyingcausativeillnessratherthandeliriumitself.17 Inpractice,withseverelyillpatients,makingaformaldiagnosisofdeliriumcanbeverydifficult.Inadditiontodelirium,anumberofdifferentialpsychiatricdiagnoseswarrantconsideration.Adiagnosisofacutefunctionalpsychosiscanonlybemadeintheabsenceofaknownmedicalcauseofthesymptoms.However,adiagnosisofpsychosisonthesegroundsaloneisdangerousandmaysimplyreflecteitherthattherehasnotbeensufficienttestingtoidentifytheunderlyingmedicalcause15orthatthetestresultshavenormalizedbutthedeliriumcontinues(forexample,inhyponatremia).Acutefunctionalpsychosisisbestdifferentiatedfromdeliriumbyconsiderationofthetypicalmentalstatefindingsinfunctionalpsychoses.Infunctionalpsychoses,globalcognitiveimpairmentislessfrequent,consciousnessremainsclearandstable,anddelusionsaresustainedandsystematized.18Dementiaanddeliriumcanbequitesimilarinpresentation;moreover,deliriumcanbesuperimposedondementia.Althoughpatientswithdementia(alone)havedemonstrablecognitivedeficits,theyariseinclearconsciousness.10,19Dementianormallyhasaninsidiousonsetandastablecourseovershortperiods. Etiologyofdeliriumintheicu TheliteratureontheetiologyofdeliriumintheICUsuggestsabroadvarietyofcausativefactors.Inadditiontophysiologicaldisturbances,othercausessuggestedincludepsychologicalstressors,sleepdeprivation,noise,andotherenvironmentalfactors.Theliteratureiscriticallyreviewedbelow,payingparticularattentiontowell-controlledstudiesratherthancasereportsorpersonalobservationsfromclinicians. PhysiologicalCauses Thefundamentalcausalinfluencesfordeliriumaremedicalfactorsandhavebeencomprehensivelyreviewedelsewhere.18,19Thesereviewshaveindicatedthatthemostcommonfactorsincludethefollowing:metabolicdisturbances,electrolyteimbalances,withdrawalsyndromes,acuteinfection(intracranialandsystemic),seizures,headtrauma,vasculardisorders,andintracranialspace-occupyinglesions.Manymedicationsandsubstancescausedeliriumthroughintoxicationorpoisoningandwithdrawal(Table1).Murray19haslisted90therapeuticdrugsthathavebeenfoundtobeassociatedwithdelirium.Tertiary-referralICUsaremorelikelytohavepatientswithmultiorgandysfunction,increasingthelikelihoodofdevelopmentofdeliriuminthesecenters.Patientswhohaveundergonecardiotomyhaveauniquesetofiatrogenicfactorscontributingtothedevelopmentofdelirium.6,12Inlessacutesettings,mostpatientswillhavemultiplecontributors.17 PremorbidCognitiveStatus Theonlypremorbidfactorsthathavebeenreliablyshowntopredictdeliriumarepriorcognitivelevelandage.Itisarguedthatagedisposesapatienttodeliriumthroughchangesinpharmacokineticsandpharmacodynamics,reducedcapacityforhomeostaticregulation,andstructuralbraindiseaseandphysiologicalprocessesassociatedwithaging.18Severalstudieshavedemonstratedhighcorrelationsbetweenpremorbidcognitionandpostoperativeconfusion,disorientation,reducedconsciousness,andevenmortality.20,21 SleepDeprivation EarlyresearchpointedtotheroleofsleepdeprivationincausingICUsyndrome.22Sincethen,despitecontradictoryresearch23andnoclearlysupportiveempiricalevidence,thisnotionhasbeenperpetuated.Anumberofcommentaryoreducationalarticles1-3,24asserttheroleofsleepdeprivationwithoutreferencetoanyprimaryresearchotherthancorrelationalstudies. Thereareanumberoffundamentalproblemswithcorrelationalstudiesandotherargumentsthatreducethelikelihoodthatsleepdeprivationdoessignificantlycontributetodelirium. First,experimentalstudiesonhealthyadultvolunteershaveconfirmedthatrapideyemovement(REM)andtotalsleepdeprivationcanleadtosomecognitiveandperceptualchanges,suchasimpairedconcentration,disorientation,andvisualdisturbances.25-27Whileperceptualanomaliesmaybeexperiencedashallucinations,theyarefrequentlyidentifiedassuchbytheexperimentalsubjects,28whichisnotthecaseinthepatientwithdelirium,whowillgenerallyhavepoorinsightintothehallucinationsordelusionsandmaybeverydistressedbythem.18TheeffectsofsleepdeprivationoncognitionandperceptioninhumansdonotmimicorevenapproachthegrossandfluctuatingcognitiveimpairmentseenindeliriumorICUsyndromeasdescribedintheliterature.27 Second,itisnotconclusivethatthelackofsleepprecedes(andthereforecancause)delirium.Internationaldiagnosticcriterialistsleepdisturbanceasanecessarydiagnosticsymptomofdeliriumratherthanbeingacauseofthedisturbance.11Onestudydemonstratedthatinsomniafollowedtheonsetofdelirium,29andanotherstudysimilarlyconcludedthattheinabilitytosleepandtheinabilitytoremainfullyalert"wereprobablytheresultratherthanthecauseofcerebraldysfunction."30 Third,aseriousconfoundingfactorincorrelationalstudiesisthattheinterruptionofsleephasbeenfoundtocorrespondtotheseverityofapatient'smedicalcondition.5Thus,whileanydeteriorationofmentalstatemightbetheresultofsleepdeprivation,itisjustaslikelytobetheresultofphysicalillness.Nostudieshaveadequatelycontrolledfortheseverityofphysicalillness. Fourth,notallcorrelationalstudieshavefoundarelationshipbetweensleepdeprivationandacuteconfusion.23Intheirreviewof80primary-datastudiesofpostoperativedelirium,Dyeretal12concludedthatlackofsleepwasnotapredisposingfactor. TheICUEnvironment Aswithsleep,otherenvironmentalfactorshavefrequentlybeencitedasbeingcausesofICUsyndromewithoutduescrutinyoftheempiricalbasisforthisconclusion.Socialisolation,immobilization,unfamiliarsurroundings,excessivenoise,andsensorymonotonyorabsenceofdiurnallightvariationhaveallbeenimplicated.TheICUenvironmentisrepletewithstress-inducinglevelsofnoise,lighting,andmovement.SeveralstudieshavedocumentedthatdecibellevelsinICUsexceedtherecommendednormallevels.31,32Whilethesefactorsmayplaceadegreeofstressonaperson,theyarenotdocumentedcausesofalteredconsciousness,delusions,orperceptualdisturbancesofthequalityorseverityseenindelirium,33norarethesefactorsnecessaryconditionsfordeliriumtooccur.Withsufficientorganicproblems,apersonwilldevelopdeliriumregardlessoftheenvironment. PsychologicalFactors ThethesisthatpsychologicaldistressmaycauseaconfusedanddeliriousstatehasbeentemptingbecausethetypeanddegreeofstressonapatientintheICUisremarkable.4Patientsaresimultaneouslysubjectedtoathreattolife,theaweofmedicalprocedures,aninabilitytocommunicateneeds,anewandthreateningenvironment,andthelossofpersonalcontrol. Earlyresearchersstudiedpreoperativepsychologicalcharacteristics,includingpersonalitytraitsandcopingstyles.Laterresearchhasexaminedotherpsychosocialfactors,suchasmaritaldistress,preoperativeanxietyanddepression,ambivalenceaboutsurgery,andhistoryofpsychosis.Dubinandcolleagues34reviewedtheliteratureonpersonalityandpsychologicalfactorspredisposingpatientstopostcardiotomydelirium,34andtheyhighlightanumberofseriousmethodologicalproblemsbeforeconcludingthattherearenopsychologicalcorrelatesofdelirium.Theystatethat norealpersonalityprofilehasbeendevelopedthatwouldallowonetopredictpostoperativeoutcome[andthat]thepostoperativemedicalstateisthemostimportantdeterminantinpostoperativedelirium.34 Anotherreviewoftheliteratureonpostcardiotomydeliriumconcludedthattherewerenosignificantcorrelationsbetweendeliriumandanypsychologicalordemographicfactor.35 Insummary,publishedresearchstronglypointstounderlyingmedicalproblems,ratherthanenvironmentalorpsychosocialfactors,astheprimarycauseofdeliriumintheICU.ThepropositionthatICUsyndromeisinfactadeliriumhasbeenarticulatedpreviously,36,37yettheconceptofadistinctICUsyndromeseemstopersistinmuchofthepeer-reviewedliterature. Management Themedicalmanagementofdeliriumis2-fold:findandreversetheunderlyingmedicalproblemsandthencontrolanybehavioraldisturbance,ifapplicable.Lipowski18hassummarizedthecoremanagementrequirementasfollows: Treatmentshouldrelatetoboththecauseandthesymptomsofdelirium.Theunderlyingcauseofthecerebraldysfunctionneedstoberemovedwheneverpossible,ortreated.Adequatefluidandelectrolytebalance,nutritionandvitaminsupplyshouldbeensured.18 Manyepisodesofdeliriumhavemorethanonemedicalcause,andanyofthesecausesmayperpetuatepsychiatricdisturbances.Appropriateinvestigationsforthepatientwhoisdeliriouspostoperativelywillincludeacompletebloodcellcount,biochemicalscreen,measurementofarterialbloodgaslevels,chestx-ray,andurinemicrobiologicaltesting.Oncedisturbancesareidentified,theymustpromptlybereversedasfaraspossible.Ifbehavioraldisturbancejeopardizesmanagement,temporarychemicalsedationmaybewarranted.Whilerecognizingitsoccasionalpotentialforcardiovascularinstability,haloperidol,0.5to2.0mg1to4timesdaily,appearstobeacceptedasthetreatmentofchoice.38,39Benzodiazepinesshouldbeavoided,exceptinthecaseofalcoholwithdrawal,astheymayperpetuatethedelirium.19 Intermsofthepsychosocialandenvironmentalmanagementofdelirium,thefollowingsuggestionshavebeencitedintheliterature:establishclearandnormalizedcommunicationwiththepatient2,19;reorientthepatienttotimeandplacefrequently40;andprovidethepatientwithanenvironmentconducivetosleep(ie,moderatenoise)andadequateanalgesia.2Ithasalsobeensuggestedthatapreoperativepsychologicalinterviewcanhelptopreventpostoperativedelirium,41,42butthisrequiresfurtherresearch.Itisimportanttonotethatwhilethesemanagementsuggestionshavesomeprimafacievalidity,thereisnoevidencefromcontrolledtrialstosupporttheirefficacy. Conclusions ICUsyndromeisatermthathasbeenusedintheliteratureforover30years,survivingthroughaseriesofreports,veryfewofwhichareprimaryresearcharticles.12ThesuppositionthattherearefeaturesintrinsictotheICUenvironmentthatcancauseapsychiatricsyndromehasrarelybeencriticallydiscussed.ThecurrentreviewindicatesthatICUsyndromedoesnotdifferfromdelirium,abetter-knownandmorewidelyresearchednosologicalentity.ThetermICUsyndromeisnothelpfulandpotentiallydangerous,sinceitimpliesthatsomecausesthatarenotorganicareresponsible,whichmaydiscouragethoroughinvestigationandtreatmentofthemedicalcauses.Unlikedelirium,ICUsyndromeisinformallyclassifiedandinconsistentlydefined,anditisnotaninternationallyaccepteddiagnosticterm.Theproperdiagnosisofadiseaseshouldfacilitatecommunicationamongcolleaguesandaidphysiciansinmakingatimelyselectionofthebesttreatmentforthatdisease.UsingthetermICUsyndromeunderminesbothactions. Deliriumoccursinatleast40%ofpatientsinhigh-dependencyunitsandICUs.Itshallmarkfeaturesareareducedlevelofconsciousness,disturbedcognition(memory,orientation,andlanguage),andperceptualdisturbances,withrapidonsetandafluctuatingcourse.Themaincausesaremetabolicdisturbances,electrolyteabnormalities,withdrawalorintoxicationsyndromes,acuteinfection,vasculardisorders,orlesionsinthecentralnervoussystem.ThereisnosoundevidencethateithersleepdeprivationortheICUenvironmentcancausedelirium.Whilethesefactorsmaylowerthethresholdfordeliriuminamedicallyillperson,thishypothesishasnotbeendirectlyinvestigated.Nopersonalityvariableshavebeenreliablyassociatedwiththedevelopmentofdelirium,andthereisnogoodevidencefortheroleofpsychologicalstressinitscause.Oldageandpremorbidcognitivedysfunctionindicateahigherriskforthedevelopmentofdelirium. WecontendthatICUsyndromeisanexampleofdeliriumandnothingmore.Futureresearchshouldbedirectedtowardimprovingtheidentification,management,andpreventionofdelirium. AcceptedforpublicationAugust13,1999. Correspondingauthor:ChristopherBasten,MPsychol,MAPS,DepartmentofMedicalPsychology,WestmeadHospital,Westmead,NewSouthWales2145,Australia(e-mail:[email protected]). 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