Journal of Critical Care (2012) 27, 533.e11–533.e19

Integrating lung ultrasound in the hemodynamic evaluationof acute circulatory failure (the fluid administrationlimited by lung sonography protocol)☆

Daniel Lichtenstein MD, PhD a, Dimitrios Karakitsos MD, PhDb,⁎

aMedical ICU, Hospital Ambroise-Pare, Faculty Paris-West, Paris, FrancebICU Department General Hospital of Athens, Athens, Greece

EPSE

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Keywords:Lung ultrasound;Echocardiography;Circulatory failure;Fluid administrationlimited by lungsonography(FALLS protocol)

Abstract In circulatory failure, fluid administration limited by lung sonography protocol uses lungultrasound artifacts and makes sequential diagnosis of obstructive, cardiogenic, hypovolemic, and septicshock. Lung ultrasound is used along with simple cardiac and vena cava analysis. Wheneverechocardiography cannot be performed, fluid administration limited by lung sonography protocol isfavored because of its simplicity and could prove contributive. It is based on the presence (B profile) orthe absence (A profile) of interstitial pulmonary edema. However, the latter does not represent actualalveolar edema, and transthoracic echocardiography is still used by intensivists as a pivotalhemodynamic measure. Tissue Doppler imaging facilitates the estimation of left ventricular fillingpressures, whereas assessing right ventricular function is of prognostic value in states of shock due tomassive pulmonary embolism and acute respiratory distress syndrome. In mechanically ventilatedpatients, poor acoustic windows are evident and performing transesophageal echocardiography may benecessary. Whenever noninvasive hemodynamic measures are inconclusive, in a deteriorating patient, apulmonary artery catheter may be placed. Ultrasound is not a therapy but a guide for treatment, andphysicians should aim to treat underlying pathologies. Despite its limitations, general chest ultrasound(lung and cardiac ultrasound) is a powerful diagnostic and monitoring tool reflecting an era of genuine“visual” medicine.© 2012 Elsevier Inc. All rights reserved.

Abbreviations: ICU, Intensive Care Unit; LU, Lung Ultrasound; TTE, Transthoracic Echocardiography; TEE, Transesophagealchocardiography; TDI, Tissue Doppler Imaging; LV, Left Ventricle; RV, Right Ventricle; LVEDP, Left Ventricular End-Diastolicressure; IVC, Inferior Vena Cava; PAC, Pulmonary Artery Catheter; PAOP, Pulmonary Artery Occlusion Pressure; PE, Pulmonary Edema;IRS, Systemic Inflammatory response Syndrome; FALLS, Fluid Administration Limited by Lung Sonography; FEEL, Focused Echovaluation in Life Support; FATE, Focused Assessed Transthoracic Echocardiography; FAST, Focused Assessed Sonography in Trauma.

☆ The authors declare that they have no conflicts of interest and that no financial support was received for this study.⁎ Corresponding author. Intensive Care Unit, General Hospital of Athens, 11527 Athens, Greece.E-mail address: karakitsosdimitrios@gmail.com (D. Karakitsos).

883-9441/$ – see front matter © 2012 Elsevier Inc. All rights reserved.ttp://dx.doi.org/10.1016/j.jcrc.2012.03.004

533.e12 D. Lichtenstein, D. Karakitsos

1. Introduction

Assessing hemodynamic function in acute circulatoryfailure is the routine work of the intensivist. The trend movesfrom pulmonary artery catheterization [1], now in decreasinguse [2-14], to transthoracic echocardiography (TTE) [15-23].Many tools are also used: analysis of inferior vena cava(IVC), continuous cardiac output devices, esophagealDoppler, pulse pressure variation, oxygen transport assess-ment, analysis of tissue oxygenation, gastric tonometry, laserDoppler flowmetry, and near-infrared spectroscopy [24-27].This substantial number allows thinking that the criterionstandard method is currently missing. Lung ultrasound (LU)was introduced in the critical care practice since 1989, due tothe pioneering work performed in Francois Jardin's IntensiveCare Unit (ICU) [28,29]. The former facilitated the promptdiagnosis of pneumonia, pulmonary edema (PE), pulmonaryembolism, pneumothorax, severe asthma, and exacerbationof chronic obstructive pulmonary disease [28-30]. There isno consensus for the use of LU as measure of thehemodynamic status in the critically ill. Hence, we analyzethe role of LU in the evaluation of acute circulatory failure byillustrating the end points of the fluid administration limitedby lung sonography (FALLS) protocol; moreover, wediscuss the advantages and disadvantages of LU comparedwith the hemodynamic assessment of shock states by TTE.

1.1. The FALLS protocol

The concept of clinical volemia indicates that we areinterested in early demonstration of fluid overload at themain vital organ, supposedly fluid-free, rather than followingindirect parameters such as changes in left ventricular (LV)or IVC size. Lung ultrasound can accurately demonstrate

Fig. 1 A lines (left) and B lines (right). The horizontal repetitions of thelines and lung sliding. Please observe 6 of the 7 characteristics of the B linto the edge of the screen without fading; well-defined; laser ray-like; echowith lung sliding (not visible in this image). Three or more B lines visibinterstitial syndrome.

interstitial edema [31] with steep learning curve [32] at anearly stage [33]. Interstitial syndrome is described from aparticular comet-tail artifact called the B line. Multiple Blines are called lung rockets (Fig. 1). Disseminated lungrockets in the critically ill indicate PE, schematically [30,34].The B profile, that is, lung rockets associated with lungsliding, indicates hemodynamic PE [30]. The normal lungsurface shows horizontal artifacts called A lines (Fig. 1). Weapply the probe on 2 standardized Bedside Lung Ultrasoundin Emergency (BLUE) points at the anterior chest wall,enabling fast protocols [35]. The predominance of A linesshowed a 93% specificity and a 97% positive predictivevalue when diagnosing pulmonary artery occlusion pressure(PAOP) 18 mm Hg or greater [36]. We have previouslydocumented a limited investigation for analyzing a simplemodel of heart, associated with lung and veins in acutecirculatory failure [29]. In connection with any otheravailable tool (history, physical examination, monitoring ofIVC dimensions, comprehensive echocardiography, etc), theintensivist will sequentially rule out the usual causes ofcirculatory failure. Other causes (anaphylaxis, spinal shock,etc) occurring in evident setting are not in our scope. Fig. 2shows the outline of the FALLS protocol used in thedifferential diagnosis of shock states: (1) obstructive shock:this limited investigation protocol first rules out pericardialtamponade, a rare but easy-to-diagnose life-threateningcondition. We are applying simple 2-dimensional echocar-diography to perform cardiac function analysis (ie, hypocon-tractility, rapid accumulation of pericardial fluid, etc) byusing transthoracic and/or subxiphoid pericardial windows.Then, we rule out pulmonary embolism, unlikely when anondilated right ventricle (RV) is seen in patients with acutecirculatory failure. If the cardiac window is not available, thewell-known BLUE protocol can be used instead, that is, lungand venous analysis with 81% sensitivity and 99%

pleural line are called A lines. The normal lung surface associates Aes: comet-tail artifacts, arising from the pleural line; long, expandingic (like the pleural line); erasing the A lines; and moving in concertle at the same intercostal space are called lung rockets and indicate

Fig. 2 Flow chart depicting the FALLS protocol in thedifferential diagnosis of circulatory failure.

533.e13LU in hemodynamic evaluation of acute circulatory failure

specificity [30]. Next, we rule out tension pneumothorax byshowing lung sliding or equivalents [30]; (2) cardiogenicshock: next, the same probe focuses on the lung, without anysetting change. The B profile on admission of patients withcirculatory failure defines cardiogenic shock, schematically.Left ventricular hypocontractility is usually associated andcan be demonstrated by echocardiography as mentionedabove. This simple approach can be found in other well-known ultrasound protocols such as focused echo evaluationin life support, focused assessed transthoracic echocardiog-raphy, and focused assessed sonography in trauma; however,analyzing these protocols is beyond the scope of this article.The B profile seen on admission with clinical suspicion ofseptic shock mandates vena cava analysis; (3) hypovolemicshock: next, we focus on shocked patients with Apredominance. Fluid administration limited by lung sonog-raphy protocol can be a therapeutic test done by adminis-trating fluid therapy to these patients, with narrowmonitoring of lung artifacts as well as circulatory conditions.Cardiac function, IVC size, and site of bleeding are alsoanalyzed. The improvement of circulation during the FALLSprotocol, while the A-predominance remains unchanged,defines, schematically, hypovolemic shock; (4) septic shock:If the signs of shock persist despite of massive fluid therapy,fluid overload will be generated. This step is immediatelydetected because B lines begin to replace A lines (a changecalled FALLS profile). This is the time for interrupting fluidtherapy. Considering that obstructive and cardiogenic shockhave been ruled out, although an hypovolemic shock would

have improved before excess fluid penetrates the lung, weinterpret the FALLS profile as indicating septic shock, theonly remaining option. Hereby, the dominant mechanism isvasoplegia, that is, time for vasopressors. This step ispreceded by slight fluid removal to position the heart at theideal point of the cardiac function, just before the flat portion.One can proceed by ordering several blood cultures,precisely indicated here, or by hemodiafiltration if alreadypresent or simply by setting patients' legs down after initiallyraising them (defining extended FALLS protocol). Let usunderline that delayed management and mortality are linkedin septic shock [37]. By following the FALLS protocol, theclinician provides a therapy conforming to standardrecommendations: early and massive fluid therapy [37],early (on admission) and massive (up to the limit). However,lung rockets seen on admission are sometimes due to acuterespiratory distress syndrome (ARDS), rarely chronicinterstitial disease. If such diseases are suspected, the limitedinvestigation opens to analysis of LV contractility, yieldingprecious information for suspecting such a condition, andvena cava analysis for guiding fluid therapy [38-40]. Inaddition, the superior vena cava can be analyzed (smalldimensions with inspiratory collapse are suggestive ofhypovolemia), which is free of intra-abdominal pressurechanges. This has been heralded using transesophagealechocardiography (TEE) [18], yet a microconvex probeprovides basic piece of information in most cases byapplying it along the neck. In addition, distinguishinghemodynamic PE from ARDS can be facilitated by applyingthe BLUE protocol [30] or other LU-based analysis [41].Lung rockets appearing during fluid therapy can be due tofluid therapy but, sometimes, to fulminant ARDS. The riskwould be to stop fluid therapy in still hypovolemic patients;thus, traditional tools should be envisaged. Another riskwould be uncontrolled fluid overload due to impropermonitoring. In fact, a permanent monitoring of lung artifactsis recommended: the “time lost” becomes “time gained” oncethe patient has been stabilized. In late stages of septic shock,hemodynamic disorders become complex [42-44], and thebest tools can be of limited effectiveness [45]. Finally,guided inotrope therapy is applied independently from theFALLS protocol, as it is not included in its decision tree.

1.2. Limitations of the FALLS protocol and cardiacfunction analysis in circulatory failure

Fluid administration limited by lung sonography protocolis based upon the presence or the absence of interstitial PE,but the latter does not represent actual alveolar edema, and itmay be considered a prestage or a poststage of alveolaredema depending on the timing of the examination and theprogress of underlying disease. A rational approach in theevaluation of circulatory failure is analyzing cardiac function[46,47]. The presence of a B profile is rather the rule than theexception in the critically ill, who are mechanicallyventilated and usually present with systemic inflammatory

533.e14 D. Lichtenstein, D. Karakitsos

response syndrome for various reasons (ie, trauma,infection, etc). Mechanical ventilation may alter strokevolume by transiently increasing intrathoracic pressure anddecreasing preload, making thus evaluation of the hemody-namic status even more complicated, whereas systemicinflammatory response syndrome may result in a B profileirrespective of intravascular volume status [48,49]. A simpleexample of complicated hemodynamics is septic shock. Thelatter has been considered, in its early stages, as ahyperdynamic state in which the cardiac output is eithernormal or increased. However, echocardiographic studiesperformed in septic patients have suggested that the termhyperdynamic is not appropriate to describe a setting inwhich the LV may be in fact hypokinetic [15,48-52]. Insevere septic shock, it may be hard to discontinue theadministration of fluids along with the administration ofvasopressors and/or inotropes; furthermore, if ARDS ispresent, which is not uncommon, thereafter, a mixture ofprogressing cardiogenic and noncardiogenic PE may well bethe case. This is difficult to interpret or to monitor with just1 tool. Notably, cardiogenic PE itself can be “mixed” in itsnature. This may be observed after myocardial infarctionthat is associated with abnormal pulmonary microvascularsodium transport/water conductance in the lung, which, inthe case of LV failure, may persist and worsen the outcome[53]. Another common example of complicated hemody-namics is about patients undergoing bypass surgery. Thesepatients have usually a B profile along with a postsurgicalpericardial effusion on the grounds of a compromised LV,whereas to be certain of the postoperative LV functionalstatus, a preoperative assessment should have beenperformed [54-56]. Finally, let us underline the usual caseof diffuse lower respiratory lung infection, whereas Bprofile is evident on the grounds of presumably decreasedintravascular volume. The aforementioned examples reflectto the various limitations of the FALLS protocol andunderline the pivotal role of TTE in the evaluation of shockstates. However, TTE requires adequate training; further-more, the acoustic window in the ICU is oftentimes poor,and thus, performing TEE may be necessary [17,53-56].

Table Echocardiographic parameters in patients with elevatedLV filling pressures

E/A ratio N2E/Pv N2E/E′ ratio N15DT b 150 millisecondsSF of pulmonary vein flow b40Percentage of enlarged left atrium size

Abbreviations: E/A, pulsed wave Doppler early and late transmitral LVfilling wave velocity ratio; E/Pv, ratio between early diastolic waveamplitude of transmitral flow and its propagation velocity into the LV;E/E′, ratio of early transmitral flow velocity E to average early tissueDoppler diastolic velocity E′; DT, deceleration time of early diastolicwave of transmitral flow; SF, systolic fraction.

Recently, LV diastolic dysfunction has been increasinglyrecognized in the presence of a normal LV ejection fractionin the ICU and may represent another source of diagnosticand therapeutic pitfalls in shock states. Volume status andLV systolic and diastolic dysfunction are linked to LVfilling pressures, which although difficult to measure, areimportant elements of hemodynamic monitoring [57-60].Pulsed wave Doppler echocardiography and tissue Dopplerimaging techniques are practical tools in the noninvasiveevaluation of LV filling pressures (Table). However,“preload independence” of early diastolic mitral annulusmotion (E′) is still debatable, and the effects of acutealterations in preload, afterload, and contractility on E′ andtheir related influence on E/E′ have not been proved[58,61]. Recent studies performed in critical care patientshave tried to correlate E/E′ and PAOP with variable success[60-64]. Echocardiographic guidelines suggested that an E/E′ ratio less than 8 accurately identified patients with anormal pressure and a ratio greater than 15 those with anelevated PAOP. In patients with intermediate values (N8 andb15), PAOP may vary widely, and the other Doppler flowmethods can be used [65]. Finally, TTE may provide simplelogistics for grading LV diastolic dysfunction by usingpulsed and tissue Doppler at the mitral valve and at themitral annulus, facilitating thus cardiac function analysis invarious cardiodynamic scenarios [60-65]. Notably, Bpredominance in LU does not always reflect elevatedPAOP in shock states (Fig. 3). Another consideration is therole of the oftentimes “neglected” RV in hemodynamicmonitoring. Right ventricular dysfunction is common in theICU, as ARDS and pulmonary embolism are major causesof acute cor pulmonale [66,67]. In addition, the effect ofpositive end-expiratory pressure and the presence ofincreased pulmonary vascular resistance due to metabolic,cardiovascular, and pulmonary factors can both affect theRV. Evaluating RV function is vital in acute circulatoryfailure due to massive pulmonary embolism and ARDS, asthe presence of significant dysfunction with these 2pathologies may alter therapy (fluid loading, vasopressors,and thrombolytics) and is of prognostic value [67].Echocardiographic evaluation of RV size and kinetics ascompared with the LV can be performed by TTE.Specifically, RV fractional area change (RV fractionalarea change = RV end-diastolic area − RV end-systolic area/RV end-diastolic area × 100%) is a simple and relativelyreproducible method to assess the effects of volume and/ordrug therapy upon the failing RV (Fig. 4) [68,69]. Pressureand volume overload of the RV cause the interventricularseptum to flatten; thus, geometric alterations of the LV areobserved (“D-shaped” configuration). The above phenom-enon of ventricular interaction alters pressure-volume loopsderived by both heart chambers; thus, information obtainedeven from a pulmonary artery catheter could be misleading.Assembling the whole hemodynamic picture of a criticalcare patient with circulatory failure may be difficult; thus, itmay be prudent to use multimodal strategies. If no safe

Fig. 3 Estimation of the ratio of early transmitral flow velocity E to average early tissue Doppler diastolic velocity E′ in 3 mechanically ventilated patients, in septic shock, who all exhibitedB profiles in LU: upper panel demonstrates E/ E′ = 7.5, reflecting normal PAOP in a case of acute respiratory distress syndrome; middle panel exhibits E/ E′ = 10.6 in a case of noncompactioncardiomyopathy, whereas more data are necessary to accurately evaluate PAOP; lower panel shows E/ E′ = 16, reflecting increased PAOP in a case of dilated cardiomyopathy.

533.e15LU

inhem

odynamic

evaluationof

acutecirculatory

failure

Fig. 4 Estimation of RV fractional area shortening by2-dimensional echocardiography.

533.e16 D. Lichtenstein, D. Karakitsos

conclusions can be drawn by noninvasive measures in adeteriorating patient, placing a pulmonary artery cathetermay offer solutions and is not an aberrant policy [70].

2. Discussion

Intensivists who follow a simple approach in hemody-namic monitoring favor the application of the FALLSprotocol. The latter is based on a correlation between B linesand PAOP and is not used as a surrogate for LV end-diastolic pressure [71,72], with various opinions on itspertinence [73-78], but as an indicator of upstreampressures, that is, PE [79,80]. Fluid administration limitedby lung sonography protocol is based on the fact thatinterstitial edema as well as elevated PAOP is constant inhemodynamic PE [81-83], and interstitial edema is a silentstep preceding alveolar edema [84,85]. Ultrasound intersti-tial syndrome appears at a preradiologic and preclinicalstage [33]. This is explained because gas exchanges,occurring at the alveolocapillary membrane [86], are notaffected. Thereafter, fluid pours into the alveoli, and clinicaldamage appears [87]. Fluid administration limited by lungsonography protocol develops Guyton's notion of a safetymargin [20], by integrating LU in the hemodynamic

evaluation of various shock states. However, it haslimitations, like any tool, but provides an on-off parameteralways available (lung windows are large), which is, inaddition, free of any constraint. Echocardiography, althoughincreasingly wide spreading, requires long training, isrestricted to wealthy areas, and is subjected to limitations.The concept of fluid responsiveness is elegant, yet it isindirect and does not consider lung tolerance to fluidtherapy as it has been applied so far [26,88-95]. One mayquestion the benefit-risk ratio of fluid therapy in septicshock. The latter exhibits high mortality despite themonitoring tools used. However, traditional tools, mainlyfluid responsiveness, can generate fluid overload becausethe initial volume status is unknown. Also note that the riskof a slight and transient overload, immediately recognizedby using FALLS protocol, is potentially less deleteriousthan unrecognized hypovolemia, in terms of macrocircula-tion and microcirculation, critical targets in septic shock.The notion that fluid overload is deleterious in septicpatients comes from studies that have not used LU [96].Carefully designed studies should determine where FALLSprotocol positions the heart along the pressure/volumefunction curve. Nevertheless, the clinical setting in whichLU is performed may be important. It is rather different toassess patients with circulatory failure in the emergencydepartment, whereas other ultrasound protocols such asfocused assessed sonography in trauma, focused assessedtransthoracic echocardiography, and focused echo evalua-tion in life support may be equally used, vs a mechanicallyventilated patient in the ICU. The clinical notion to use LUas part of a multimodal approach including TTE and/orTEE along with other hemodynamic measures is interest-ing. Those who favor advanced noninvasive models ofhemodynamic monitoring pose the question: why use alimited investigation protocol based on an already limitednoninvasive method? Surely, LU does provide significantinformation, but gathering additional hemodynamic data bya multimodal noninvasive approach may address thecomplicated hemodynamic scenarios observed in the ICU[97]. Fluid administration limited by lung sonographyprotocol is designated as a “user-friendly” approach forintensivists who wish to perform rapid hemodynamicanalysis by implementing simplified cardiac functionanalysis along with vena cava analysis using LU data askey decision points. Advanced echocardiographic analysis,which has been extensively used in the evaluation ofvarious circulatory states, is technically demanding. If bothapproaches result in the same therapeutic decisions,simplicity should be considered and favored; however,further studies are required to clarify this notion. Trans-thoracic echocardiography and LU-based hemodynamicanalysis of various shock states do not represent necessarily2 distinct methods; in fact, these 2 approaches are bothparts of the same noninvasive, yet powerful, diagnostic andmonitoring tool designated as general chest ultrasound.However, the latter is not a therapeutic option but rather a

533.e17LU in hemodynamic evaluation of acute circulatory failure

guide for treatment; thus, physicians should always befocused to treat underlying pathologies.

3. Conclusions

In circulatory failure, the FALLS protocol uses anunexpected parameter, LU artifacts, and makes sequentialdiagnosis of obstructive, cardiogenic, hypovolemic, andseptic shock. In all settings where cardiac acoustic window issuboptimal, echocardiography skills limited, no time, or noechocardiographic machine, the FALLS protocol will provecontributive. However, in-depth evaluation of LV and RVfunction may be crucial in various complex hemodynamicscenarios in the ICU. Lung ultrasound and TTE comprisetogether a powerful diagnostic and monitoring tool, namely,general chest ultrasound that reflects an era of genuine“visual” medicine in the ICU.

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