Файловый архив студентов. Файловый архив студентов.
1327 вузов, 5482 предметов.
/ Регистрация
FAQ Обратная связь Вопросы и предложения
Добавил:
kiopkiopkiop18@yandex.ru t.me/Prokururor I Вовсе не секретарь, но почту проверяю Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Ростовский Государственный Медицинский Университет
Предмет:
Медицина общая
Файл:

Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_2804_Библиотеки_им_академика_М_И_Перельмана

.pdf
Скачиваний:
0
Добавлен:
02.09.2026
Размер:
21 Мб
Скачать
☆
upper gastrointestinal (GI) bleeding, which can be prevented by appropriate use of pharmacologic prophylaxis.
Theprimaryindicationsforstressulcer prophylaxisarethepresenceofasignificantcoagulopathy
(platelets<50k,internationalnormalizedratio>1.5,orpartialthromboplastintime>2upper limits
ofnormal) or the use of mechanical ventilation >48 hours. Theother indications for prophylaxis
includeahistoryofanupperGIbleedinthelastyear,presenceofbrainorspinalcordinjury,orany
two of the following: occult bleeding for ≥6 days, use of high-dose steroids (>250 mg of
hydrocortisone),sepsis,oranintensivecareunit(ICU)stay>1week.
Ahistamine-2receptorantagonistorproton pumpinhibitorcanbeusedforprophylaxiswithsome
controversyonwhatagentispreferred.
Theuseofulcerprophylaxismayincreasetheriskofnosocomialinfections,butbenefitsarelikely
greaterthanrisksintheabovepatients. Oxygentoxicity:BreathinghighFIO2canleadtoexcessivefreeradicalgenerationandresultinlung
injury.
Reducing FIO2tothelowesttolerableoxygensaturation (O2saturationof90%or PaO2 of65 mm
Hg) is advisable. There is evidence that tolerating hyperoxia after intubationmay worsen patient
survival.
13
LiberationFromMechanicalVentilation
Parametersdemonstratingreadiness towean:Dailyassessment ofreadinessforextubationshould be done once the underlying disease process begins to resolve and minimal ventilator support is required.Thefollowingcriteriashouldgenerallybemetbeforeextubation:
Minimalventilatorsupport:FIO2≤40%,PEEP5cmH2OtomaintainSpO2>90%.
Arterial blood gas: pH and PaCO2 should be at the patient’s baseline; particularly important for
patientswithchronicCO2retention.
Ventilation requirement: Minute ventilation should be <10 L/min and respiratory rate <30
breaths/min.
Mentalstatus:Patientshouldbeawake,alert,andcooperative.
Secretions: Secretions should be thin, scant in amount, and easily suctioned; patient should not
requiresuctioningmorefrequentlythanevery4hoursbeforeextubation.
Strength:Patientshouldhavestrongcoughandbeabletoliftheadoffthebedandholditinflexion
for>5seconds.
Breathingtrial:PatientshouldbeabletogeneratespontaneousVT>5mL/kgIBW.
Rapidshallowbreathingindex(RSBI):RSBIshouldbe≤105.Definedasratioofrespiratoryrate
toVTinliters(f/VT).RSBI>105accuratelypredictsweaningfailure,butRSBI≤105islessaccurate
atpredictingweaningsuccess.
33
Patency of airway: In patients with concern for laryngeal edema (e.g., angioedema, traumatic
intubation),cuffleakshouldbecheckedbeforeextubation.Absenceofcuffleakshouldgenerally
precludeextubation,andpatientsshouldbetreatedwithIVcorticosteroidsfor12–24hoursbefore
extubation.
34
Some patientsfelttobe readytoextubatebased onall objectivecriteria will still failextubation.
Failureratesashighas23.5%havebeenreported.
35
Weaningstrategies:Sedationinterruptionandbreathingtrialsfor30–120minutesshouldbedone dailyandis themostimportantpredictor oftimely liberationfrom mechanical ventilation.36Weaning
strategiesincludethefollowing:
https://t.me/med1917
PSV:Notime-triggeredbreaths,butpatientremainsconnectedtotheventilator.PEEPisusuallyat5
cmH2O,withlowlevelsofpressuresupport(5–10cmH2O)duringspontaneousbreathing.
T-piece/spontaneousbreathingtrial:Patientisremovedfromtheventilatorbutremainsintubated.
Endotracheal tube is connected to a heated, humidified circuit with minimal or no supplemental
oxygen.End-tidalCO2monitoringmaybeusedforadditionalsafety.
SIMV:Usedmostfrequentlyinsurgicalandneurosurgicalpatients.Setrespiratoryrateisgradually
decreasedoverhourstodaysuntilpatientisprimarilybreathingspontaneously.
SIMVhasthepoorestweaning outcomesofall techniques.However,neitherT-piece norPSVhas
proventobemorepredictiveofsuccessfulextubation.
37
Managementfollowingextubation:Patientsneedtobecloselymonitoredfollowingextubation.Good airwayclearanceandoxygenationdecreasetheriskofreintubation.
Extubation to NPPV: In patients with COPD who are intubated for acute respiratory failure,
extubation to NPPV is associated with a reduction in mortality and health care–associated
pneumonia.38 More generally, in patients with chronic hypercapnic respiratory failure, two trials
have found that the use of NPPV reduces rates of reintubation following extubation.
39,40
 Similar benefitofNPPVhasnotbeendemonstratedinotheretiologiesofrespiratoryfailure. Extubation to HFNC: The use of HFNC may also have a beneficial role in the prevention of postextubationrespiratoryfailureinselectlow-riskpatients.Whenpatientswererandomlyassigned toHFNCversusconventional oxygentherapyafterextubation,patients whoreceived HFNCwere lesslikelytobeintubatedwithin48–72hours.
41,42
OtherstudieshaveshownHFNCtobenoninferior
whencomparedwithNPPVinpreventingreintubation.
43
Failure to wean: Defined as inability to liberate from mechanical ventilation 48–72 hours after resolutionofunderlyingdiseaseprocess.Factorsthatshouldbeconsideredincludethefollowing:
Endotrachealtubeswithsmallerinnerdiameterincreaseairwayresistanceandmaymakebreathing trialsmoredifficult. Useofneuromuscularblockadeisassociatedwithprolongedweakness,particularlywhenusedwith corticosteroids.
44
Critical illness myopathy and polyneuropathy places the patient at risk for recurrent respiratory failure. Psychiatric illnesses (delirium, anxiety, PTSD, etc.) may interfere with SBTs and other standard weaningprotocols. Acid–basedisturbancesmaymakeliberationfrommechanicalventilationdifficult.
Non–anion gap metabolic acidosis causes compensatory increase in minute ventilation (respiratoryalkalosis)tonormalizepH,whichcanleadtotachypneaandrespiratoryfatigueupon extubation. Metabolic alkalosis causes blunting of ventilatory drive and decrease in minute ventilation (respiratoryacidosis)tomaintainnormalpH,whichcanleadtohypercapniauponextubation.
Shock
GENERALPRINCIPLES
Aprocessinwhichbloodflowandoxygendeliverytotissuesarederanged,leadingtotissuehypoxia andresultantcompromiseofcellularmetabolicactivityandorganfunction. Maingoaloftherapyisrapidcardiovascularresuscitationtoreestablishtissueperfusion.
https://t.me/med1917
Definitivetreatmentrequiresreversalofunderlyingprocesses.
ClassificationsofShock
HemodynamicpatternsassociatedwiththedifferentshockstatesarelistedinTable8-5.
TABLE8-5
HEMODYNAMICPATTERNSASSOCIATEDWITHSPECIFICSHOCKSTATES
TypeofShock CI SVR PVR SvO
2
RAP RVP PAP PAOP
Cardiogenic ↓ ↑ N ↓ ↑ ↑ ↑ ↑
Hypovolemic ↓ ↑ N ↓ ↓ ↓ ↓ ↓
Distributive N−↑ ↓ N N−↑ N−↓ N−↓ N−↓ N−↓
Obstructive
a
↓ ↑−N ↑ N−↓ ↑ ↑ ↑ N−↓
a
EqualizationofRAP,PAOP,diastolicPAP,anddiastolicRVPestablishesadiagnosisofcardiactamponade.
CI,cardiacindex;N,normal;PAOP,pulmonaryarteryocclusionpressure;PAP,pulmonaryarterypressure;PVR,pulmonary vascularresistance;RAP,rightatrialpressure;RVP,rightventricularpressure;SvO2,mixedvenousoxygensaturation;SVR,
systemicvascularresistance.
Distributive:Shockcausedbymassivevasodilationandimpaireddistributionofbloodflow,resulting intissuehypoxia. Usuallyassociated with hyperdynamic cardiac function,unless cardiac functionis somehowimpaired(seelaterdiscussionofcardiogenicshock).
Primaryetiologiesaresepticshockandanaphylacticshock.Septicshockismostcommonlyseenin medicalICUsandwillbefurtherdiscussedinthenextsection.AnaphylaxisisdiscussedinChapter
11,AllergyandImmunology.Otherlesscommontypesincludeneurogenicshockandadrenalshock.
Hemodynamicparameters will generally demonstrate increased cardiac output (CO), decreased systemic vascular resistance (SVR) due to vasodilation, and elevated central venous oxygen saturation(ScvO2)duetoineffectiveoxygenextractionbytissue.
Primarygoalsoftherapy
Volume resuscitation: Owing to massive peripheral vasodilation, patients have a functionally decreased oxygen-carrying capacity, requiring volume resuscitation. IV crystalloid fluids are primarilyused. Treatmentofunderlyinginfection:Inadequateinitialantimicrobialtherapyisanindependentrisk factor for in-hospital mortality inpatients with septic shock, so timely, effective antimicrobial therapyisacornerstoneoftreatment. Removaloftheoffendingagentinanaphylacticshock. Cardiovascularsupportwithvasoactive agents (e.g.,norepinephrine).Vasoactiveagentswillbe
discussedinmoredetailinalatersection. Hypovolemic: Shock causedbya decreaseineffectiveintravascular volumeanddecreased oxygen­carryingcapacity.
Primaryetiologiesarehemorrhagic(e.g.,trauma,gastrointestinalbleeding)orfluiddepletion(e.g., diarrhea,vomiting). Hemodynamic parameters will generally demonstrate a decreased CO, increased SVR, and decreasedScvO2duetoincreasedoxygenextractionbyperipheraltissue.
https://t.me/med1917
Primarygoalsoftherapy
Volumeresuscitation:IVbloodproductandcrystalloidareusedforresuscitationofhemorrhagic
andfluiddepletionshock,respectively,withgoalmeanarterialpressure(MAP)of60–65mmHg.
Overresuscitation may be detrimental in hemorrhagic shock and patients without significant
comorbiditiesmaytoleratelowerhemoglobinlevels(7g/dL)thanpreviouslybelieved.
Definitive treatment of underlying etiology of volume loss: For hemorrhagic shock, surgical
interventionmaybenecessary. Obstructive: Shock caused by obstruction of the heart or great vessels, resulting in decreased left ventricularfillingandcardiovascularcollapse.
Primaryetiologiesarepulmonaryembolism,cardiactamponade,andtensionpneumothorax. Hemodynamic parameters will generally demonstrate decreased CO,normal to increased SVR,
andnormaltodecreasedScvO2. Primarygoalsoftherapy
Supportive: Although patientsarepreloaddependent,excessive fluidadministrationcanleadto
rightventricularoverloadandimpairmentofLVfilling,therebyworseningshock.
Definitive therapy involves relieving the obstruction (e.g., thoracostomy in the case of a
pneumothorax,andpericardiocentesisintamponade).
Inacarefullyselectedgroup ofpatients,thrombolytictherapymaybebeneficialinpatientswith
pulmonaryemboli. Cardiogenic: Shock caused by left ventricular systolic failure, resulting in decreased CO and subsequentinsufficientoxygendistribution.
Primaryetiologiesaremyocardialinfarction,acutemitralregurgitation,andmyocarditis. HemodynamicparameterswilldemonstratedecreasedCO,increasedSVR,anddecreasedScvO2.
Primarygoalsoftherapy
Mitigation of pulmonary edema: NPPV or endotracheal intubation with mechanical ventilation
reduces afterload, thereby encouraging forward flow, as well as preload. Additionally, the
applicationofpositive pressuretothealveolar spacecausespulmonaryedemafluidtomove to
theinterstitialspace.
Careful fluid management: Adequate preload to optimize ventricular function is important, but
volumeoverloadwillworsenrespiratorystatus,socarefulfluidmanagementisnecessary.Volume
removal (whether via diuresis or hemodialysis) is often a critical component of early
management.
Definitive therapy for underlying cardiac disease: In the event of myocardial infarction,
percutaneousrevascularizationshouldbeperformedinatimelyfashion.
Supportive:InotropicagentssuchasdobutaminemaybeusedtoaugmentCO.Otherinotropesare
discussed in “Pharmacologic Therapies.” Mechanical circulatory assist devices, including left
ventricularassistdevicesandintra-aorticballoonpumps,maybenecessaryinpatientswhodonot
respondtomedicaltherapy.
SepticShock
Definitionofsepsis:Sepsisisdefinedasalife-threateningorgandysfunctioncausedbydysregulation ofthehostresponsetoaninfection.
Sepsis was previously identified based on the presence of at least two systemic inflammatory responsesyndrome(SIRS)criteria:
Tachypnea:Respiratoryrate>20breaths/minorPaCO2<32mmHg
Whitebloodcellcount<4000cells/μLor>12,000cells/μL
https://t.me/med1917
Tachycardia:Pulse>90bpm
Hypo-orhyperthermia:Temperature>38°Cor<36°C
The new sepsis guidelines now identify organ dysregulation in sepsis as an increase in the SequentialOrganFailureAssessment(SOFA)scoreof≥2.
45
Septic shock is a subset of sepsis identified by persistent hypotension requiring vasopressors to maintaina meanarterial bloodpressure≥65 mmafteradequatevolume resuscitation.Mortalityin
thesepatientsis 40%. Management of septic shock: Management of septic shock involves early aggressive volume resuscitationandattemptingtoachievehemodynamicstabilityquickly.
46
Volumeresuscitation:Patientsshouldbegintoreceiveatleast30mL/kgIBWIVcrystalloidfluid
withinthefirsthourofpresentation.47Smalleramountsoffluidmaybeneededifthereisconcomitant
heartfailureorpulmonaryedema,whereasadditionalvolumemayberequiredifthepatientremains
volumeresponsiveaftertheinitial30mL/kgbolus.Parameterstodeterminevolumeresponsiveness
(discussed in “Hemodynamic Measurements”) should be closely monitored during volume
resuscitationtopreventvolumeoverload.
A recentRCTfoundthatbalancedcrystalloids (i.e.,lactatedRinger solution)maybeassociated withlowerratesofrenaldysfunction andevenimprovedmortalitywhenusedascomparedwith normalsaline.
48
Severaltrials havenot foundsignificantbenefitinalbuminadministration whencompared with crystalloidinsepticpatients.
49
Cardiovascular support: Vasoactive medications may be necessary if volume resuscitation is
insufficienttomaintainMAP≥65mmHg.Norepinephrinehasbecomethefirst-lineagentafterit
was demonstrated that dopamine had more adverse events.50 Vasopressin is frequently used as a
second-line agent. Mechanisms of action and other agents are discussed in “Pharmacologic
Therapies.”
Timely, effective antimicrobial administration:Delaysinstarting appropriateantimicrobialsare
associated with increased mortality.51 The Surviving Sepsis Guidelines recommend starting
antibioticsimmediatelyafterobtainingbloodcultures,ifpossible.
47
Sourcecontrol:Ifaspecificanatomicalsourceofinfectionisidentified(e.g.,necrotizingsofttissue
infection),interventionforsourcecontrolshouldbeperformedassoonasreasonablypossible.
52
Earlygoal-directedtherapy:Protocol formanagementofthefirst6hoursofsepsisproposed by
Rivers et al. in2001.46 Widely adapted in practice before recent multicenter, prospective, RCTs
calleditseffectivenessintoquestion.
53,54
However,thesestudieswerelimitedbypracticechangesin
controlgroup(Figure8-3).
https://t.me/med1917
Figure 8-3  Early goal-directed therapy protocol.(Adapted from Rivers E, Nguyen B, Havstad S, et al. Early goal-
directedtherapyinthetreatmentofseveresepsisandsepticshock.NEnglJMed.2001;345:1368-1377.)
*Although included in the original early goal-directed therapy protocol, more recent trials have demonstrated a trend
towardincreasedharminpatientswhoreceivemoretransfusions;currentSurvivingSepsisGuidelinesdonotrecommend
transfusingtoachieveHctof30%.CVP,central venouspressure;Hct,hematocrit;IBW,idealbodyweight;MAP,mean
arterialpressure;ScvO2,centralvenousoxygensaturation.
Lactateclearance:Lactateclearanceisassociatedwithimprovedmortalityinsepticpatients.55The
most recentSurvivingSepsis Guidelinesrecommendtargeting resuscitationtonormalizelactatein
patientswithelevatedlactatelevels.
47
Procalcitonin(PCT): PCTis a biomarker that may aid in diagnosing sepsis, assessing treatment
response, and determining antibiotic duration. An elevated PCT >0.5 ng/mL is suggestive of a
bacterial infectionwhile a PCT <0.1 ng/mL makes bacterial infection less likely.56 Some studies
have shownthatuse of PCTmay reduce the unnecessaryusage of antibiotics.57 However, caution
https://t.me/med1917
mustbeused,asalowPCTdoesnotexcludethepossibilityofaseverebacterialinfection.
PharmacologicTherapies
VASOCONSTRICTIVEANDINOTROPICAGENTS
Norepinephrine:Causespotentvasoconstrictionviaα1-andβ1-adrenergicactivity. Preferredagentin septicshock.
Vasopressin: Causes vasoconstriction via three different G-peptide receptors. Primarily used as an adjuncttonorepinephrine.Weakevidencethatitmayhavemortalitybenefitovernorepinephrineinless severesepticshock(definedasrequiringtreatmentwithnorepinephrine5–14μg/mintomaintainMAP ≥65mmHg).
58
Epinephrine:Hasinotropicandvasoconstrictivepropertiesinadose-dependentfashionowingtoα1- andβ-adrenergicactivity.Atlowdoses(≤0.05μg/kg/min),itincreasesCOandslightlyreducesSVR
owingto predominant β activity. At higher doses (>0.05 μg/kg/min), vasoconstriction predominates owingtoincreasedα1activity.Preferred agent foranaphylactic shock,andisalso frequentlyusedin
cardiogenicshock. Phenylephrine: Selective α1-receptor agonist causing vasoconstriction of larger arterioles. Few
studiessupportingitsuseinsepticshock. AngiotensinII:RecentstudieshaveinvestigatedangiotensinIIwhichengagesthe renin–angiotensin– aldosteronesystem.ThesestudiesshowedthatangiotensinIIincreasedbloodpressureinpatientswith vasodilatoryshock.
59
Dobutamine:Inotropicagentthatreducesafterloadandincreasesstrokevolumeandheartrateviaβ1- agonistactivity.Goodagentforcardiogenicshockbutincreasesriskofcardiacarrhythmias.
Dopamine:Hasinotropic,vasodilatory, andvasoconstrictive properties inadose-dependentfashion duetoactiononperipheralα1-receptors,cardiacβ1-receptors,andrenalandsplanchnicdopaminergic
receptors.Atdoses<5μg/kg/min,primarilybehavesasavasodilator,increasingrenalbloodflow.At dosesof5–10μg/kg/min,behavesasaninotrope.Atdoses>10μg/kg/min,behavesasavasopressor. Isassociatedwithahigherrateofcardiacarrhythmiasthannorepinephrine.
50
Milrinone: Phosphodiesterase IIIinhibitor thathaspositive inotropic effect,causingincrease inCO. Also causes systemic vasodilation, which decreases afterload, making it an alternative option for cardiogenicshock. Regardingvenous access, low-dose norepinephrine, phenylephrine,and epinephrine may be infused peripherally for a limited period of time. However, central access is preferred as medication extravasationcanleadtolocalischemia.
Ifextravasationoccurs,phentolamine(anα-antagonist)canbeinjectedintotheareaofextravasation
toreduceischemicinjury.
PeripheraladministrationofvasopressinandangiotensinIIisnotrecommended.
ADJUNCTIVETHERAPIES
Corticosteroids:Relativeadrenalinsufficiencymaycontributetorefractoryhypotensionduringseptic shock. Datado notsupportthe useofcorticosteroids inmild septicshock. However,corticosteroids shouldbeconsideredonanindividualbasisinpatientswithmoresevereshock,particularlyinpatients chronically on steroids. Generally, hydrocortisone 200–300 mg daily divided on a q6–8h basis is given.Previoustrialshaveshownfasterresolutionofshockwhenadministeringhydrocortisone,butno difference in mortality.
60,61
 Another recent trial showed a benefit in 90-day mortality when
https://t.me/med1917
hydrocortisone (50 mg every 6 hours) and fludricortisone (50 µg daily) were administered in conjunction.
62
Sodiumbicarbonate: No evidence supports the use of bicarbonate therapy in lactic acidemia from sepsis with a pH≥7.15. Effectofbicarbonateon hemodynamics andvasopressor requirementswith moresevereacidemiaisunknown,butbicarbonateisoftenrecommendedinpatientswithseverelactic acidemia(pH<7.1)whoarehemodynamicallyunstable. Methylene blue: Selective guanylate cyclase inhibitor, thereby mitigating nitric oxide–mediated vasodilation.Observationalstudieshavedemonstratedbeneficialeffectsonhemodynamicparameters, buteffectsonmorbidityandmortalityareunknown.
63
HemodynamicMeasurements
AlthoughCVP,MAP,andSvO2/ScvO2areusedastherapeuticendpointsintreatingshock,thereis evidencethattheseparametersdonotreflectintravascularvolume.Thereisagrowingbodyofevidence
thatdynamicparameters,includingpulsepressurevariationandinferiorvenacava(IVC)diameters,may betterreflectintravascularvolume,butitisunclearthattheuseoftheseleadstoimprovedoutcomes.
Staticparameters
CVP:Anapproximationofrightatrialpressureand,therefore,preload.Shouldbemeasuredfroman
internal jugular or subclavian venous catheter because readings from femoral catheters are
influenced byintra-abdominal pressuresandthusinaccurate.Thereis a poorrelationshipbetween
CVPandblood volume,64butlow values (<4mmHg) should generallylead to fluidresuscitation
withcarefulmonitoring.
65
ScvO2/SvO2: ScvO2 is a surrogate that is often used to reflect SvO2, which is thepercentage of
oxygenboundtohemoglobininbloodreturningtotherightsideoftheheart.ScvO2ismeasuredfrom
an internal jugular or subclavian venous catheter, while a true SvO2 must be measured with a
pulmonary artery catheter (PAC). Normal values are 65%–75%. A high value often represents
decreasedoxygenconsumption(commonlyseeninmitochondrialdysfunctionwithsepsis),whereas
low values indicate inadequate oxygen delivery (oftenduetolow COstates such as cardiogenic
shock).PreviousguidelinesrecommendedtargetinganScvO2>70%withdobutamineadministration
ifneeded,thoughmorerecenttrialshaveshownthatusinglactateclearanceasaresuscitationgoalis
noninferior.
66
PACs:APACcatheterprovidesdirectmeasurementsofpressuresintherightatrium,rightventricle,
andpulmonaryartery,aswellasapulmonarycapillarywedgepressure.Previouslycommonlyused
inthemanagementofsepticshockandARDSbutdidnotaffectmortalityormorbidity.
67
Dynamicparameters
EsophagealDoppler:ADopplerprobeisplacedinto theesophagusandrotatedtomeasureblood
flow through the descending aorta. System can be used to calculate CO and stroke volume, and
correlates well with CO as measured by PAC.68 Predicts volume responsiveness in critically ill
ventilatedpatientswithoutspontaneousbreathing.
69
Pulse pressure variation (ΔPp): Requires arterial line placement. Calculated as the difference
betweenmaximalandminimalsystolicbloodpressuresmeasuredoveronerespiratorycycledivided
by the mean of those values. ΔPp of 13% was an accurate predictor of fluid responsiveness in
mechanicallyventilatedpatientswithoutspontaneousbreathing.
70
IVCdistensibilityindex(dIVC):Calculatedasthe differencebetweenmaximal andminimal IVC
diametermeasuredoveronerespiratorycycledividedbytheminimalIVCdiameter.dIVCof18%
discriminatedbetweenvolumerespondersandnonresponderswith90%sensitivityandspecificityin
mechanically ventilated patients without spontaneous breathing in one study,71 but more recent
https://t.me/med1917
studieshaveshownthismethodtobeapoorpredictoroffluidresponsiveness.
72
Thoracicbioreactance: Anoninvasive device is applied tothe chest andmeasures bioreactance
acrossthethoraxusingsensorpadsplacedonapatient’sthoraxsurroundingtheirheart.Bloodflow
(which is predominately in the aorta in the thorax) causes phase shifts in impedance, which is
detectedbythesensors.From thesemeasurements,strokevolumeandCOcanbeestimated.There
are conflicting data on the ability of thoracic bioreactance devices to reliably determine fluid
responsiveness.
73,74
CriticalCareUltrasound
Theuseofbedsideultrasonographyhasgreatlyexpandedrecentlyandisrapidlybecomingstandardof careinICUs.Coursesincriticalcareultrasonographyarebecomingmorereadilyavailableandare necessaryforcompleteproficiency.Thissectionisintendedtoserveasanoverviewofbasicconcepts only.Criticalcareultrasoundshouldbeusedasanadjuncttootherclinicaldata.
Basicconcepts:Airandcalcifiedstructurestransmitsoundwavespoorly.Free-flowingfluidstransmit soundwaveswell.
Basicdefinitions
Echogenicity:Theabilityofanobjecttoreflectsoundwaves.
Hyperechoic: Structures that reflectsound waves well;shows as white on ultrasound (e.g.,bone,
pleura,lung).
Hypoechoic: Structures that reflect sound waves poorly; shows as gray on ultrasound. Deeper
structuresarealsomorehypoechoicowingtoattenuationwithdistance(e.g.,lymphnodes,adipose
tissue,muscle).
Anechoic:Containingstructures thatallowsoundwaves topass throughfreely;showsasblackon
ultrasound(e.g.,bloodvessels,transudativepleuraleffusion).
Ultrasoundtofacilitatevascularaccess:MoredetailedinstructionsareavailableintheWashington Manual of CriticalCare, Section XIX.Use of ultrasound to guide central venous access results in
increasedsuccessandreducedcomplicationrates.
Location: Ultrasound guidance is most commonly used for internal jugular and femoral venous
access.
Beforestartingtheprocedure:Bothinternaljugularandfemoralveinsshouldbescannedtoevaluate
foraberrantanatomyorvenousthrombosis.
Afterapplyingthesterilefield:Theprobeispositionedsothattheneedleisvisualizedfortheentire
durationofaccessingthevessel.
During theprocedure:Followinginsertionoftheguidewire, the lengthofthevessel is scannedto
ensurethattheguidewiredidnotinadvertentlyenteranyadjacentarteries.
Aftertheprocedure:Lungultrasoundcanbeusedtoruleoutapneumothorax. Cardiacultrasound:Includesfivestandardviews,reviewedbelow.Usesbodytransducer.Intendedto facilitateassessment ofvolumeresponsiveness,globalleftandrightventricularsystolicfunction,and valvularfunction.
Parasternal long-axis view: Probe is placed adjacent to the sternum in the left third to fifth
intercostal spacewiththeorientationmarkerpointingtoward thepatient’srightshoulder.Theright
ventricularoutflowtract,leftventricularcavity,ascendingaorta,mitralvalve,andleftatriumshould
bevisualized.Assessesforpericardialeffusion,leftandrightventriculardysfunction,andvalvular
pathologies.
Parasternalshort-axisview:Proberemainsadjacenttothesternumintheleftthirdtofifthintercostal
space,butorientationmarkerisrotated90degreesclockwisetopointatthepatient’sleftshoulder.
https://t.me/med1917
Cross-sectionalviewoftheleftandrightventriclesatthelevel ofthe papillarymusclesshouldbe
visualized.Assessesforpericardialeffusionandleftandrightventriculardysfunction.
Apicalfour-chamberview:Probeisplacedbetweenthemidclavicularandmidaxillarylinesofthe
leftlateralchestbetweenthefifthandseventhintercostalspaces,underneaththeleftnipple,withthe
orientation marker pointed at 3 o’clock. The left and right ventricles and atria, as well as the
tricuspid and mitral valves, should be visualized. Assesses left and right ventricular size and
function.SeeFigure8-4.
Figure 8-4  Cardiac ultrasound.Left (A): normal apical four-chamber view. A, apex; RV, right ventricle; RA, right
atrium; LV, left ventricle; LA, left atrium. Right (B): demonstrates same view in a patient with right ventricular
hypertrophyanddilation.
Subcostal long-axis view: Probeis placed below thexiphoid process withthe orientationmarker
pointed at 3 o’clock. The left and right ventricles and atria should be visualized. Assesses for
pericardialeffusionandleftandrightventriculardysfunction.Maybeusedforrapidassessmentof
cardiacfunctionduringperformanceofcardiopulmonaryresuscitation.
IVClongitudinalview:Proberemainsbelowthexiphoidprocess,butorientationmarkerisrotated
90 degrees counterclockwise to point at 12 o’clock. IVC in the longitudinal axis should be
visualized.AssessesIVCdiameterduringtherespiratorycycletodeterminevolumeresponsiveness. Thoracicultrasound:Includesfourstandardpositions,performedbilaterally.Usesthebodytransducer on theabdominal setting toexaminelung parenchyma;vascular transducermay be usedfordetailed examinationofthepleura. Intended to facilitatethe diagnosis of pleural effusion,pulmonaryedema, pulmonaryconsolidation,andpneumothorax.Alsousedtoguideasafethoracentesis.
Probeplacement:Bedsidelungultrasoundinemergency(BLUE)sprotocol,intendedforimmediate
diagnosisofacute respiratoryfailure,definesfourareasforinvestigation.75Theorientationmarker
shouldbepointedtowardthepatient’shead.
UpperBLUEpoint:Midclavicularline,secondintercostalspace LowerBLUEpoint:Anterioraxillaryline,fourthorfifthintercostalspace Phrenicpoint:Midaxillaryline,sixthorseventhintercostalspace;locationofthediaphragm Posterolateral alveolar and/or pleural syndrome point: Posterior to the posterior axillary line,
fourthorfifthintercostalspace Anatomic landmarks and ultrasound appearance: Knowledge of the normal sonographic appearanceofthoracicanatomyisparamounttoidentifyingkeystructures.
https://t.me/med1917
Соседние файлы в папке Библиотека им академика М.И. Перельмана
Помощь Обратная связь Вопросы и предложения Пользовательское соглашение Политика конфиденциальности