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PatientPositionDuringAnesthesiaByDavidRoyGoddenCRNA,MSNLectureObjectivesGainanunderstandingofsafepositioningbasicsIdentifythepotentialnerveinjuriesfrommaskventilationStatethecorrecthandandarmpositioningforsupine,lateraldecubitusandpronepositions.Beabletorecitethepotentialnerveinjuriesofeachpatientposition.Identifythecomplicationsofthesittingposition.ObjectivesContDefineandunderstandthehemodynamicsofeachpatientposition.Understandandbeabletoverbalize-thatmeansknowthoroughly-therespiratoryandautonomicresponsesofdifferingpatientpositionswhileawakeandundergeneralanesthesia.DiscussPostOperativeVisualLoss(POVL)CaseStudy:ComplicationsofPronepositionLookforKeyPointsPositioningisoftenacompromisebetweenwhatisrequiredforsurgicalexposureandpatientcomfort!Donotplacesedatedoranesthetizedpatientsinpositionsthattheyarenotcomfortablewithwhenawake.IfindoubtaboutpatientssafetyhavethepatientassumethepositionontheORtablebeforeinductiontoseehowtheytoleratetheposition.PatientpositioningisthejointresponsibilityofORNursing,AnesthesiaandSurgery.Allthreeindividualsandgroupsthatrepresentthemwillbeheldliableiferrorsinpositioningcausepatientharm.Document!DocumentationofPositioningTheonlythingthatrepresentswhatwasdoneintheoperatingroominacourtoflawisyourtestimonyandyourdocumentation.Howmuchdoyouthinkyoucanrememberfromonecasetothenextandhowmuchofyour“story”willthecourtofficers“believe”withoutyourcarefuldocumentationintheanesthesiarecord?Whattodocument?Pre-operativepatientlimitationsinmovementstrengthandnerveabnormalities.Doesthepatienthavenumbnesstinglingorlossofsensationtoanyextremitypre-operatively?Doesthepatienthavefootdrop?MaskInjuriesPotentialforcornealabrasionisalwayspresentwhenmaskventilatingpatients.Facestrapswhicharetightacrossthepatientsfacewithprolongedusemaycauseinjurytothefacialnerve.Whatarethefivebranchesofthefacialnerverememberingthemnemonic,“Twozebrasbitmycat”Thebucalbranchismostlikelyinjuredwithafacestrapcompression.TemporalZygomaticBucalMandibularcervicalDorsalDecubitusPositionsGravityeffectsbloodflowandmuchofpulmonarymechanics.Humans,giraffesanddinosaursshareonethingincommon.Whatisit?InthesupinepositiongravityequalizesbloodpressuregradientsbetweenheartandarteriesintheheadandlowerextremitiesCorrectAnatomicalPositionWhatistheventralsurface?WhatisthedorsalsurfaceNote:DorsaltodorsalandventraltoventralDorsalDecubitusPositionsHeadtilteitherupwardsordownwardswillchangethepressuregradients.Amovementof2.5cminverticalelevationwillchangethebloodpressure2mmHg.IntheparturientanIVbagundertherighthipwillshiftthegraviduterustotheleft.HaveyouheardofAorto-cavalsyndrome?HandpositioningLyingatattentionrequirescorrectarmandhandpositiontominimizethechancesofnerveinjuries.Armsaretobelessthan90degreeslateralizedfromthethoraxincorrectanatomicalpositionlookingattheshoulders.Thiswillminimizethechanceofbrachialplexusinjury.ArmsatsideofbodymustbeincorrectdorsaltodorsalalignmentwiththearmssupinatedORpalmstowardthebodyisOKaswell.Theulnarnervepassesclosetothesurfaceoftheskininthemedialcondyleoftheelbow.Theolectranonwillprotectthenerveifplaceddownwards.Radialnerveinjuryispossiblewithetherscreencompressiontothelateralarm.Radialnerveinjurymayresultinwrist drop.WhatisSupinationCorrectanatomicalpositionislyingatattentionorPalmsareventralsurfacesoventraltoventralDorsaltodorsalmeanbackofhandstoback.HeaddownthingsLoweringtheheadwillincreasethepressureinthecerebralveinswhichmayleadtovascularheadache,congestionofnasalmucosaandconjunctivainhealthyindividuals.Thismayleadtoedemainthelarynxaswell.Thescleraisthewindowtothevocalcords!Headloweringinpatientswithintra-craniallesionswillexacerbatetheconditionraisingCPPandICP(whatstheformulaforthis?)AutonomicfunctionAorticarchandcarotidsinushousebarorecetorsthatarepartofthebodieshomeostaticmechanismtomaintainbloodpressurewithinanarrowrange.Increasedfiringofthereceptorswhenstretchedfromanincreaseinbloodpressureispartofanegativefeedbackloop.Theincreasedfiringfromthebaroreceptorsenhancestheparasympatheticnervoussystemloweringbloodpressureandslowingtheheartrate.Rememberthis!Whatarethenervesresponsibleforthebaroreceptorreflexes?RespiratoryEffectsRespiratorymechanicswillsufferintheheaddownpositionhow?ReviewWestszonesofthelung.Normalexcursionofthediaphragminheaddownpositionisimpededandincreasetheworkofbreathing.Intheparalyzedmechanicallyventilatedpatient,higherpeakpressureswillberequiredforadequateventilation.SupinepatientsdevelopVQ mismatchduetovascularcongestioninthedorsalportionsofthelungandchangesincompliance.Thedorsallung(nowzone3)willhavereducedcompliance.Passiveventilationtendstodistributegaspreferentiallytothemoreeasilydistensiblesubsternalunitswherepulmonarybloodflowvolumeisless(Barish,2006).MoreRespiratorythingsTopreventdevelopmentofsignificantV-Qimbalanceduringuseofcontrolledventilation,tidalvolumesmustbeusedthataregreaterthantheaverageamountthatissufficientforthespontaneouslybreathingconsciouspt.Compareandcontrasttheawakespontaneouslybreathingptandtheparalyzedmechanicallyventilatedptinthelateralposition.HowwouldyouattempttodecreasePeakpressuresduringmechanicalventilationintheparalyzedanesthetizedpatient?Hint:deepenanesthetic,musclerelaxation,decreaseVtandincreaseRate,changeI:Eratiofrom1:2to1:1.5.ConsiderPressureControlventilationduetoitsdeceleratingwaveform.VariationsintheDorsalDecubitusPositionSupineotherwiseknownaslyingatattention.Placesstrainonlowersegmentsoflumbarspine.Lawnchairisamorephysiologicallytoleratedpositionduetodecreasedstretchonlowerback.Frogleg(healtohealwithlateralizationofknees)forperonealexaminationsmayplaceexcessivestretchonback,hipsandpelvicstructures.Padunderknees.Complicationsofexcessivestretchmayinclude1)postoperativehipandbackpain;2)dislocatedhiporfractureofanosteoporoticfemur;3)obturator nerve injury.ComplicationsofDorsalDecubitusPressureAlopeciaduetoprolongedcompressionofhairfollicles.Mostalopeciaoccursbetweenthe3rdand28thpostoperativedaywhilere-growthusuallyoccurswithin3months(Barish,2006).Placementofgelpadordonutunderheadisworthwhile.Frequentrepositioningoftheheadiswarranted.ComplicationsofDorsalDecubitusPressurepointreactionsoccurwhenbonyprominencesareunsupportedforprolongedperiods.Hypothermiaandhypotensionenhancetheischemicprocess.Theheals,elbowsandsacrumshouldbegelpadded.NOTE:Therearenostudiesprovingdecreasedincidenceofperipheralneuropathiesduetogelpadding.Backpainduetolossoflordosis.Lawnchairpositionbest.LithotomyPositionLithotomypositiontraditionallyhasbeenusedduringgynecologicandurologicsurgery.Thehipsareflexed80to100degreesandthehipsareabducted30to45degreesfrommidline.Hipflexiongreaterthan90degreesmaycausestretchoftheinguinalligamentsandimpingethelateral femoral cutaneousnerveswhichpassthroughtheinguinalligamentwhichleadstonumbness in the lateral thigh.Thelegsshouldbemovedintoandoutofpositionsimultaneously.Thekneesarebroughttomidlineandthelegsslowlyunflexedtothesupinepositionattheendofthesurgicalprocedure.ComplicationsinLithotomyLegelevationcausesincreaseinvenousreturnandtransientriseinCOandICP.Alterations in pre-Load is most responsible for hemodynamic changes during anesthesia.AbdominalvisceraisdisplacedcephaladdecreasingVtandincreasingpeakpressures.Backpainfromlossoflordoticcurvatureofspineinlithotomyposition.LithotomyComplicationsDANGERtofingers.Watchcarefullywhenhandsaretuckedandraisingorloweringfootboard.Injurytothecommonperoneal nerve.ThisistheMOST COMMOM nerve injury to the lower extremitiesaccountingfor78%ofalllowerextremitymotorneuropathiescausedbycompressionofthenervebetweenthelateralheadofthefibulaand“candycane”barstirrups.Durationofsurgerygreaterthan2hoursisapredictorofincreasedincidenceoflowerextremityneuropathy.MoreComplicationsofLithotomyPositioningCompartmentsyndromeisararecomplicationbutoccursinlithotomypositionduetoinadequateperfusiontotheraisedextremity.Ischemia,edemaandthepossibilityofrhabdomyolysisoccursfromtheincreasedpressureinthefascialcompartment.Foryounumberheads,compartmentsyndromeoccurredinabout1inamillionforpatientsinsupinepositionandabout1in9,000forptsinlithotomyposition.Whatdoyouthinkaboutlithotomy?Danger!LateralDecubituspositionLateraldecubituspositionisusedforsurgeriesonthorax,retroperitonealstructuresorhip.V-Qmismatchincreasesduetogravitationalforces.Perfusionisgreatestindependentstructuresordownlungwhileventilationisbetterinnondependentlung.Useof“ChestRoll”incidentallymisnamedaxillaryroll.Thepresenceofthechestrollistopreventcompressioninjurytothebrachialplexus.Monitorthepulseinthedependentarmplease.LateralDecubituspositionNondependentarmis“airplaned”orsupportedwithpillowsandnotallowedtobeabductedgreaterthan90degrees.Placepillowbetweenkneeswithdependentlegflexed.Pressurepointsincludeacromionprocess,iliaccrest,greatertrochanter,peronealnerveandlateralmaleolus.ComplicationsofLateralDecubitusEyeandearinjuries.Makesurethatdownsideearandeyeare“free”frompressure.Useadonutrollfortheear.UseoftheOpti-guardoreyeguardisconsideredusefulinlateralpositions.Neckflexionneedstobeavoided.Positionneckmidlinewithsupportingtowels.ComplicationsofLateralDecubitusSuprascapularnervestretchfromthecircumductionofthedependentshoulder.Thechestrollshouldpreventthis.Long thoracic nerveinjuryfromlateraldecubituspositionhasbeendocumented.Winging of the scapulaisthetypicalclinicalsign.TheserratusanteriormuscleissolelysuppliedbythelongthoracicnervewhichbranchesfromC5C6andC7.KidneyPositionKidneypositionisaflexedlateraldecubituspositionwherethetableisflexedto“openup”thelateralstructuresforsurgicalexposure.Flexpointshouldbeunderiliaccrestnotribcage.Stabilizethepatienttopreventmovementandshiftscaudadonthetablesothatthekidneyrestmaynotrelocateditselfintothedownsideflank.VentilationissuesagainmayoccurduetodependentlungcompromiseandV-Qmismatching.PronePositioningPronepositionisprimarilyusedforsurgicalaccesstoposterioraspectofthespine,posteriorfossaofskull,buttocksandperirectalareasorposteriorportionsofthelowerextremities.Pronepositioningrequiresplanning.Inductionandintubationofthetracheaisaccomplishedwhilepatientissupineonstretcher.IVaccessisperformedaswellasarterialcatheterplacementpriortoturningproneonoperatingroomtable.WouldyouconsideruseofLMAorextubationintheproneposition?SupportingdevicesforProneTheheadissupportedusuallymidline.Mayfieldtongsareusedforcraniotomycasesintheproneposition.AtLACweusetheProneViewwithamirrortoseethefacialstructureswhilethepatientisprone.Turningtheheadtothesidemaybeusedbutlateralrotationoftheneckmaycompromisecarotidorvertebralarterialbloodflowandmayrestrictvenousdrainage.Eyeprotectionisrequired.SupportingdevicesforProneSupportofthethoraxwithfirmbolsterswhichareplacedunderthepatientssidesfromclavical to iliac crest.Thisallowsthebellytohangfreeandincreasesventilationwhilepreventingaorto-cavalcompression.Breastsareplacedmedialandcephaladwhilegenitalsareinsuredtobenoncompressed.ArmplacementinProneptsPlacementofthearmsiseitheratthesidesofthepatientorforwardalongsidetheheadonpaddedarmboards.Paddingoftheelbowisrequired.Abductionofthearmsshouldbelimitedtolessthan90degreestopreventexcessivestretchofthebrachialplexus.Anklesmaybesupportedwithabendinthekneestoreducestretchtothelumbarspine.CalfcompressionstockingsareroutinelyusedtopreventvenousstasisorbloodpoolingwithreductioninDVT.ComplicationsofPronePositionPronepositionisoneofthemorechallengingpositionstotheanesthetist.Eyeandearinjuriesaremorecommoninthisposition.EyeprotectionwithOpti-guardiswarranted.Scleraledemaiscommoninpronepatients.Blindness.Permanentlossofvisioncanoccurafternonocularsurgicalproceduresespeciallyinpatientintheproneposition!Spinesurgerywithitsblood loss,hypotension and anemiamayallconspiretogethertoproduceoptic nerve ischemia.AdditionalProneProblemsNeckinjuriesduetomisalignment.Brachialplexusinjuriesduetoexcessivestretchormisalignmentofshoulders.Breastorgenitalinjuriescausingpainordysfunction.Notgood.Medialplacementofbreastsisrecommended.Abdominalcompressioninjuriesmaybealleviatedwiththeuseofbolsters.ProneProblemsKneeinjuriesareespeciallyprevalentintheobeseorinthosewithpathologicconditionsofthekneespreoperatively.Documentandpadthekneesheavily.Injurytothedorsumofthefeetisalsopossible.ThoracicOutletsyndrome.Howdoyoutestforit?DidyouforgetaboutPOVLintheProneposition?SittingPositionSeeattachedarticleinanesthesiapatientsafetynewsletter.Beachchairpositionmaycausedecreasedcerebralperfusion,CVA,andbraindeath-really.ApsfNewsletterarticleREADIT!Majorriskofsittingpositionishypotension.SittingpositionandtheriskofAIREMBOLIS.MoreSittingPositionSittingpositionisoftenusedforoutpatientshouldersurgeryandposteriorfossaapproachesWhy!Whenotherpositionsarelessdangerous!Hemodynamiceffectscanbedramatic.Poolingofbloodinthelowerpartofthebodyandthesubsequentdecreaseincerebralperfusion.Rememberthe2mmHgrule?TherewillbeaquestionaboutthisHintHint.Ofteninshouldersurgerywhileinthesittingpositionthesurgeon“requests”hypotensionreallyitstrue!ComplicationsofSittingPositionPotentialcomplicationsduetoflexionoftheneckwhichcanimpedebotharterialandvenousbloodflowthroughtheneck.Flexionoftheendotrachialtubemayleadtoexcessivepressureonthetongueleadingtomacroglossia.Neckflexionmaybemeasuredandkepttoacceptablelimitswithtwofingerbreadthsdistancebetweenchinandsternum.Venousairembolismisaseriouscomplicationofsittingpositionandthereasonforitsrareuse.VenousAirEmbolismThislifethreateningconditionmayoccuranytimeasurgicalsiteisabovetheleveloftheheart.Therearenovalvesinthecerebralvenouscirculationandtheriskofvenousairembolismisconstantinthesitting positionwhentheoperativesiteevolvestheposteriorfossaormayoccurinspinal surgerywhenprone!Rememberthis!Venousairembolismmaybemanifestedascardiacdysrhythmias,arterialoxygendesaturation,pulmonaryhypertensionorfrankcardiacarrest.Actionstotakeifyoususpectanairembolismistoaskthesurgeonstofloodthefieldwithsalineandtoapplybonewaxtoboneyedges.Forfurtherdiscussionrefertoyourneurolecture.OverviewofNerveinjuriesTheClosedClaimsProjectconductedbytheASAevaluatedadverseanestheticoutcomesin1990.Ulnar neuropathy remains the MOST frequent(28%)of all nerve injuriesfollowedbybrachialplexus(20%).Etiologyofperipheralnerveinjuriesremainslargelyunknown.Mostofthenerveinjuriestoulnarandbrachialplexusoccurredinpatientswithproperpositioningandadequatepadding.Ulnarneuropathyresultsinaninability to abduct or oppose the fifth finger,deminishedsensationinthefourthandfifthfingersandeventual“claw”hand.UlnarNeuropathyCurrentthinkingisthatulnarneuropathyismultifactorialandnotalwayspreventabledespiteroutineuseofarmboardsandpadding.Ulnarneuropathyismostcommoninoldermen,diabetesmellitus,vitamindeficiency,alcoholism,cigarettesmokingandcancer.Prevention?Avoidexcessivepressureonthepostcondylargrooveofthehumerus,limitabductionofthearmtolessthan90degrees,keepthehandandforearmeithersupinatedorinaneutralpositionwithpalmsfacingthigh.BrachialPlexusInjuryThebrachialplexusissubjecttoinjuryduetostretchingorcompressionasaresultofitslongsuperficialcourseintheaxilla.Armabductiongreaterthan90degrees,lateralrotationofthehead,asymmetricretractionofthesternumanddirecttraumaallmaycontributetobrachialplexusinjury.Cardiacsurgeryandsternotomyisassociatedwithahigherincidenceofbrachialplexusinjury.Shoulderbraceshavehistoricallybeenaculpritinbrachialplexusinjuryleadingtotheirrareuse.Thecompressionofproximalrootsorlateraldisplacementofthebracescanstretchtheplexuswhentheshouldersaredisplaced.Usenonslidingmattressinsteadofshoulderbraces.LowerExtremityNerveinjuryLithotomypositionisassociatedwithinjurytocommonperonealandsciaticnerves.Thesciaticnervemaybestretchedwithexternalrotationofthelegorwithhyperflexionofthehipsandextensionoftheknees.TheSaphenousnervemaybeinjuredifthemedialkneeiscompressedLowerExtremityNerveInjuryThecommon peroneal nervewhichisabranchofthesciaticmaybeinjuredwithcompressionbetweentheheadofthefibulaandthemetalframeof“candycane”stirrupswhenthepatientisinthelithotomyposition.ThisistheMost commonnerveinjuryinlowerextremities!Commonperonealnerveinjuryresultsin Foot Drop!MorenerveinjurystuffMediannerveinjurymaybecausedby“searching”foranIVintheanticubitalfossaresultingintheinabilitytoopposethumbandthelittlefinger.ThepostoperativeneuropathythatmustbereferredtoaneurologistimmediatelyisanyMOTORdeficitfollowingsurgery.ThankyouforyourattentionandIamlookingforwardtoseeingyouintheOR.Sowhatisitlikeontheothersideofthatsteepmountain?CaseStudy:POVLinPronePositionA58yearoldanesthesiologisthaschronicbackpainandisscheduledforlaminectomyataUniversityMedicalSchoolTeachinghospital.Thecaseisscheduledfor6hoursbutrunsover-really?Ofcourse-thisisapronepositioncasewithover500mlofbloodloss.CaseStudyAfterthesuccessfulcompletionofthesurgerythepatienthasvisualcomplaintsincludingflashingcolors.Fundoscopicexamwasnormal.Overthenextweeksavisualfieldofvisionlossof70percentisreported.CaseStudyDiscussion:WhatarethedataconcerningPOVL.Whatrolldoesanesthesiaplayintheinformedconsentforpronecases?WhatistheliabilityoftheanesthesiaproviderforPOVL?ReferencesapsfNewsletter,“BeachChairPositionDecreaseCerebralPerfusion”Vol22,No.2,25-40.apsfNewsletter,“Ifmyspinesurgerywentfine,whycantIsee?”Vol23,No.1,1-20.Bararshallofit!MillersAnesthesia6thed.Chapter28.
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