Validity of lung ultrasound FALLS-protocol in differentiating types of shock in critically ill patients

Tamer S.A Mawla; Aliaa A Elhameed; Areeg A.Y Abdallah; Osama M Momtaz

doi:10.4103/roaic.roaic_28_22

ORIGINAL ARTICLE

Year : 2022 | Volume : 9 | Issue : 4 | Page : 275-282

Validity of lung ultrasound FALLS-protocol in differentiating types of shock in critically ill patients

Tamer S.A Mawla, Aliaa A Elhameed, Areeg A.Y Abdallah, Osama M Momtaz
Department of Critical Care, Fayoum University, Fayoum, Egypt

Date of Submission	05-May-2022
Date of Decision	21-Aug-2022
Date of Acceptance	23-Aug-2022
Date of Web Publication	29-Dec-2022

Correspondence Address:
MD Tamer S.A Mawla
Department of Critical Care, Fayoum University, El Naboy El Mohands Street, El Abody Region in front of El Nada Hospital, Fayoum 11563
Egypt

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/roaic.roaic_28_22

Abstract

Background Acute circulatory collapse is one of the most familiar challenges in ICUs. It is considered that artefacts generated by lung ultrasound (LUS) can help in diagnosis and management. FALLS-protocol using LUS is a tool proposed for the management of unexplained shock.
Objectives To investigate the role of LUS FALLS-protocol in differentiating types of shock in critically ill patients.
Patients and methods A total of 50 patients presented with undiagnosed shock. Fast bedside echocardiography and LUS FALLS-protocol were applied along with inferior vena cava diameter and collapsibility measurement.
Results A total of 19 patients with septic shock on presentation had A profile in all of them and AB profile in three of them, and after resuscitation, they were transformed to B profile with 100% sensitivity, 90.5% specificity, 90.5% positive predictive value (PPV), and 100% negative predictive value (NPV). Overall, 16 patients with hypovolemic shock had A profile in all of them on presentation and after resuscitation, with 100% sensitivity, 94.1% specificity, 88.9% PPV, and 100% NPV. Moreover, eight patients with cardiogenic shock had B profile in all of them on presentation with 100% sensitivity, 95.2% specificity, 80% PPV, and 100% NPV; three patients with obstructive shock had A profile in all of them on presentation, with 100% sensitivity, 25.5% specificity, 7.9% PPV, and 100% NPV; and two patients with anaphylactic shock had A profile in all of them on presentation and transformed to B profile after resuscitation with 100% sensitivity, 50% specificity, 9.5% PPV, and 100% NPV. Our findings showed preference of FALLS-protocol than inferior vena cava diameter and collapsibility in directing fluid therapy.
Conclusion Bedside chest ultrasound FALLS-protocol should be considered in the resuscitation pathways with a possible significant effect on patient management.

Keywords: FALLS-protocol, lung ultrasound, shock

How to cite this article:
Mawla TS, Elhameed AA, Abdallah AA, Momtaz OM. Validity of lung ultrasound FALLS-protocol in differentiating types of shock in critically ill patients. Res Opin Anesth Intensive Care 2022;9:275-82

How to cite this URL:
Mawla TS, Elhameed AA, Abdallah AA, Momtaz OM. Validity of lung ultrasound FALLS-protocol in differentiating types of shock in critically ill patients. Res Opin Anesth Intensive Care [serial online] 2022 [cited 2023 Mar 26];9:275-82. Available from: http://www.roaic.eg.net/text.asp?2022/9/4/275/365791

Background

In ICU, fluids are used to optimize organ perfusion, fulfill fluid deficiency, and give medication or nutrition. However, excessive fluid transfusion induces multiorgan failure, prolong intensive care and hospital length of stay, and even decreased survival [1].

Despite evidence regarding harmful effects of overhydration in ICU, routine administration of fluids without a safety limit and frequent prescription of diuretics without a targeted end point are common practice. These practices may be attributed to the drawbacks of currently used volume-assessment methods [2].

In recent years, lung ultrasound (LUS) has emerged as a novel tool to predict overhydration and has been successfully used in patients from the ICU, nephrology, and cardiology departments [2].

Acute circulatory collapse is one of the most familiar challenges in ICUs. It is considered that artefacts generated by LUS can help in its diagnosis and management. FALLS-protocol using LUS is considered as a tool proposed for the management of unexplained shock [3].

LUS now is considered a noninvasive, safe, and rapidly available tool and is already a part of different diagnostic algorithms for many life-threatening conditions. LUS may provide a valuable safety threshold to fluid therapy and optimization of volume status [4].

The sonographic signs of increased extravascular lung water are the artefacts called B lines. B lines are defined as discrete laser-like vertical hyperechoic reverberation artefacts that arise from the pleural line (previously described as ‘comet tails’), which extend to the bottom of the screen without fading, and move synchronously with lung sliding. Three or more B lines visible at the same intercostal space are called lung rockets and indicate interstitial syndrome. However, the horizontal repetitions of the pleural line are called A profile [5].

Objective

Our study was aimed to investigate the role of LUS (FALLS-protocol) in differentiating types of shock in critically ill patients.

Patients and methods

The study was conducted in the Critical Care Department of Fayoum University Hospital and enrolled 50 adult ICU patients. Ethical approval was obtained from the ethical review committee of the Faculty of Medicine, Fayoum University, Egypt in January 2020 prior to the study beginning. An informed written consent was taken. Patients included were expected to stay at least 48 h in the ICU.

All patients were subjected to full past and present history, examination, routine laboratory tests, severity score (APACHE II), ECG and echocardiography evaluating the left and right side functions, and LUS. Excluded from our study were patients aged less than 18 years, patients with chest trauma, and post-CPR patients.

Lung ultrasound

A bedside LUS was performed with the patient in a supine position, using the Philips HD11XE ultrasound system with a convex probe (2.0–5.0-MHz frequency). The lungs were scanned from the second to the fourth intercostal spaces on both sides, at parasternal, midclavicular, anterior axillary, and midaxillary lines.

The schematic decision tree of FALLS-protocol (fluid administration limited by lung sonography) applied is as follow [6] ([Figure 1] and [Figure 2]):

Ruling out obstructive shock: simple cardiac sonography to exclude pericardial tamponade and pulmonary embolism and LUS for A-profile to exclude pneumothorax.
Ruling out cardiogenic shock: absent lung rockets (B-lines) ruled out a pulmonary edema owing to cardiogenic shock.
Ruling out hypovolemic shock: ‘FALLS-responders’ represent the fluid therapy (30 ml/kg) should improve the clinical signs of a hypovolemic shock (A-profile was benefit from fluids).
Ruling out septic shock: the fluid therapy not apple to improve circulations, eventually B-profile generated. At this step, simple fluid transfusion should be stopped and vasopressors must be started.
Anaphylactic shock occurs in suggestive settings, usually, and spinal shock is rarely an issue.

Figure 1 FALLS-protocol used in the differential diagnosis of shock states (schematic decision tree) [6].

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Figure 2 A profile (left) and B profile (right).

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Inferior vena cava diameter and collapsibility

Inferior vena cava (IVC) diameter and collapsibility were measured during inspiration and expiration using the M-mode in the subxiphoid view. We applied less than 50% as a cutoff point of collapsibility index to identify fluid responders, mainly patients with hypovolemic and septic shock [7] ([Figure 3]).

Figure 3 Subcostal IVC window. The hepatic vein junction to the IVC and the IVC junction to right atrium are confirmatory landmarks. IVC, inferior vena cava.

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IVC on M-mode was obtained, the maximum (dIVC max) and minimum IVC diameter (dIVC min) was measured, and IVC collapsibility index (IVCCI) was calculated.

Statistical analysis

The collected data were organized, tabulated, and statistically analyzed using SPSS software statistical computer package, version 22 (SPSS Inc., Chicago, Illinois, USA). Quantitative data were presented as mean±SD and range. Independent t test or dependent t test, when appropriate, was used as a test of significance. Categorical data were presented as numbers and percentages. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess the validity of different LUS profiles in predicting different types of shock.

Results

Our study was conducted in medical ICU of Fayoum University Hospital, from January 2020 to September 2021. A total of 50 patients presented with shock were enrolled in this study.

Demographic characteristics of our study

The mean age of patients in our study was 53.7±19.2 years, with 30 (60%) male patients.

Risk factors

Overall, 18% of our study group patients (nine patients) were hypertensives, 20% diabetics (10 patients), and 24% smokers (12 patients).

Vital signs and hemodynamics

They are shown in [Table 1].

Table 1 Vital signs and hemodynamics

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Echocardiographic findings

Ejection fraction was 57.4±12.1, and mean pulmonary artery systolic pressure was 32.4±13.5.

Arterial blood gases

They are shown in [Table 2].

Table 2 Aarterial blood gases

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Lung ultrasound findings

A profile was found in 38 (76%) patients before resuscitation and 16 (32%) patients after resuscitation.
B profile was found in 10 (20%) patients before resuscitation and 21 (42%) patients after resuscitation.
AB profile was found in three (22%) patients before and after resuscitation.
C profile was found in two (4%) patients before and after resuscitation.

Types of shock according to primitive diagnosis by lung ultrasound

Before resuscitation: it was found that 11 (22%) patients had cardiogenic shock, three (6%) patients had obstructive shock, and 36 (72%) patients had other types of shock.
After resuscitation: it was found that 19 (38%) patients had septic shock, 16 (32%) patients had hypovolemic shock, eight (32%) patients had cardiogenic shock, three (6%) patients had obstructive shock, two (4%) patients had anaphylactic shock, and two (4%) patients had mixed septic and cardiogenic shock.

Validity of different lung ultrasound profile in prediction of type of shock

Nineteen patients diagnosed as having septic shock:
1. US profile on presentation (before resuscitation).
  1. A profile was found in all of them, with 100% sensitivity, 32.3% specificity, 47.5% PPV, and 100% NPV.
  2. AB profile was found in three of them, with 15.8% sensitivity, 100% specificity, 100% PPV, and 66% NPV.
2. After resuscitation:
  1. B profile was found in all of them, with 100% sensitivity, 90.5% specificity, 90.5% PPV, and 100% NPV.
  2. AB profile was found in three of them with 15.8% sensitivity, 100% specificity, 100% PPV, and 66% NPV.
Sixteen patients diagnosed as having hypovolemic shock:
1. US profile on presentation (before resuscitation).
  1. A profile was found in all of them, with 100% sensitivity, 35.3% specificity, 42.1% PPV, and 100% NPV.
  2. C profile was found in one patient, with 6.3% sensitivity, 97.1% specificity, 50% PPV, and 68.8% NPV.
2. After resuscitation:
  1. A profile was found in all of them, with 100% sensitivity, 94.1% specificity, 88.9% PPV, and 100% NPV.
  2. C profile was found in one of them with 6.3% sensitivity, 97.1% specificity, 50% PPV, and 68.8% NPV.
Eight patients diagnosed as having cardiogenic shock:
1. B profile was found in all of them, with 100% sensitivity, 95.2% specificity, 80% PPV, and 100% NPV.
Three patients diagnosed as having obstructive shock: discriminated from other types of shock by echo and IVS diameter and collapsibility.
1. US profile on presentation (before resuscitation).
  1. A profile was found in all of them, with 100% sensitivity, 25.5% specificity, 7.9% PPV, and 100% NPV.
2. After resuscitation:
3. A profile was found in all of them, with 100% sensitivity, 27% specificity, 7.8% PPV, and 99% NPV.
Two patients diagnosed as having anaphylactic shock:
1. US profile on presentation (before resuscitation).
  1. A profile was found in all of them, with 100% sensitivity, 25% specificity, 5.3% PPV, and 100% NPV.
2. After resuscitation:
  1. B profile was found in all of them, with 100% sensitivity, 50% specificity, 9.5% PPV, and 100% NPV.
Two patients diagnosed as having mixed septic and cardiogenic shock:
1. B profile: was found in all of them, 100% sensitivity, 83.3% specificity, 20% PPV, and 100% NPV.
2. C profile was found in one of them. C profile was found with 50% sensitivity, 97.9% specificity, 50% PPV, and 97.9% NPV.

Inferior vena cava and CVP in septic shock

There was no statistically significant difference regarding IVC diameter before and after resuscitation in septic shock (1.71±0.42 vs. 1.80±0.43, respectively), with P value of 0.6, and IVC collapsibility before and after resuscitation (59.83±13.0 vs. 60.0±14.0, respectively), with P value of 0.8, and central venous pressure (CVP) before and after resuscitation (4.74±4.81 vs. 4.79±4.73, respectively), with P value of 0.331.

Inferior vena cava and CVP in hypovolemic shock

There was a statistically significant difference regarding IVC diameter before and after resuscitation in hypovolemic shock (1.43±0.63 vs. 1.47±0.65, respectively), with P value of 0.033, and IVC collapsibility before and after resuscitation (64.35±11.41 vs. 60.85±11.61, respectively), with P value of 0.027, and CVP before and after resuscitation (−0.88±3.79 vs. 0.94±3.07, respectively), with P value of 0.001.

Discussion

We followed FALLS-protocol in a stepwise approach, which facilitated rapid, noninvasive, dynamic differentiation of types of shock and defined patients responding to fluid therapy (FALLS-responders) [6].

Obstructive shock was firstly suspected and excluded in three patients (two of them pulmonary embolism and one of them had tension pneumothorax) guided by LUS: A-profile was found in all of them with 100% sensitivity, 25.5% specificity, 7.9% PPV, and 100% NPV.

This also correlated with our final diagnosis, clinical examination, and ECHO findings, showing the pivotal role of FALLS-protocol in excluding this type of shock.

This agreed with Lichtenstein et al. [8] who reported that if pericardial effusion, right ventricle dilatation (suggesting pulmonary embolism), and tension pneumothorax are absent, obstructive shock can be excluded, schematically.

This disagreed with Abdel-Aal et al. [9], who found normal LUS A-profile in only two and C-profile in three of 19 patients with obstructive shock included in their study.

Then, cardiogenic shock as a next step in the approach was investigated. It was found in the eight patients who presented with cardiogenic sock had B profile on LUS, with 100% sensitivity, 95.2% specificity, 80% PPV, and 100% NPV. This agreed with Lichtenstein et al. [10], who reported that while scanning the lungs, when lung rockets are absent, cardiogenic shock can be ruled out.

LUS finding was in correlation with clinical picture and echocardiography. This was in concordance with Price et al. [11], who reported that echocardiography and LUS can be used to identify inadequate cardiac output and presence of congestion.

On the contrary, Abdel-Aal et al. [9] found normal LUS A-profile in two patients, C-profile in one patient, and B-profile in five patients out of 11 patients with cardiogenic shock included in their study.

Then, according to the approach followed, patients in our study who were neither obstructive nor cardiogenic remaining with A-profile were called FALLS-responders and underwent fluid therapy, waiting to be differentiated between septic and hypovolemic shock depending on clinical improvement of shock parameters or not and concordant appearance or not of lung artefacts (B-profile).

Accordingly, in our study group, after fluid therapy, we found that 16 patients diagnosed as having hypovolemic shock kept their A-profile without transformation to B-profile, even though they experienced clinical improvement.

Using LUS, A profile was found in all of them, with 100% sensitivity, 94.1% specificity, 88.9% PPV, and 100% NPV, and C profile was found in one of them with 6.3% sensitivity, 97.1% specificity, 50% PPV, and 68.8% NPV. This agreed with Lichtenstein et al. [8], who described that the improvement of clinical signs of circulatory failure with an unchanged A-profile under fluid therapy reasonably defines hypovolemic shock.

This disagreed with Abdel-Aal et al. [9] who found that in four patients diagnosed as having hypovolemic shock included in their study, one had A-profile, one had C-profile, and one had B-profile.

This correlated with our IVC diameter and collapsibility measurements, which had a significant finding in relation to response to fluid therapy. This agreed with Youssifa et al. (2020) [12].

On the contrary, we found that 21 patients showed a different response to fluid therapy in the form of transformation of A-profile into B-profile, indicating subclinical interstitial pulmonary edema, which alarmed us to cease fluid therapy (FALLS end point) and begin adding the appropriate vasopressor and guided our diagnosis toward distributive shock, 19 patients of them had septic shock with B profile in all of them with (100% sensitivity, 90.5% specificity, 90.5% PPV, and 100% NPV), and AB profile in 3 patients of them with (15.8% sensitivity, 100% specificity, 100% PPV, and 66% NPV); the other 2 patients had anaphylactic shock with B profile after resuscitation in both of them (100% sensitivity, 50% specificity, 9.5% PPV, and 100% NPV).

This concept agreed with Gargani L et al. (2007), who reported that interstitial edema is an early and infraclinical step of pulmonary edema [13].

On the contrary, those findings disagreed with Esraa F. Abdel-Aal et al. [9] who found that in 30 patients with septic shock included in their study, only 14 expressed C-profile and 1 showed normal A-profile.

However, at this step, our IVC diameter and collapsibility measurements did not show any significant finding in contrast to LUS in early detection of interstitial edema in our study group. This agreed with Elliot Long et al. (2017) [14].

In our present study, 2 patients who were preliminary assessed by LUS using FALLS-protocol were diagnosed as having isolated cardiogenic shock, but as a last diagnosis, they were diagnosed as having mixed shock mostly cardiogenic and septic done, mainly with the help of IVC measured diameter and collapsibility in concordance with the clinical picture of the patients.

Their LUS finding from start showed B-profile in both of them, with 100% sensitivity, 83.3% specificity, 20% PPV, and 100% NPP. C-profile was seen in one of them, with sensitivity 50%, specificity 97.9%, PPV 50.0%, and NPP 97.9%. This agreed with Lichtenstein et al. (2014), who found that if a B-profile is seen on admission, the FALLS-protocol cannot be used. The diagnosis is usually cardiogenic shock but sometimes lung sepsis. The IVC roughly correlates with volemia [15].

This disagreed with the study by Abdel-Aal et al. [9], which included 2 patients with mixed shock and showed the following findings in their LUS: 1 patient showed consolidation, and the other showed no specific finding.

Therefore, our measurements showed that IVC diameter and collapsibility in hypovolemic shock showed significance, with P value of 0.033 and 0.027, respectively, in our hypovolemic patients on admission and after fluid responding according to FALLS-protocol. This agreed with Youssifa et al. [12], who found a significance difference of both IVC diameter and collapsibility in 45 traumatized patients in their study, with P value less than 0.01.

On the contrary, same measurements of IVC diameter and collapsibility were done in septic shock on admission and after stoppage of fluid therapy owing to FALLS-end point, which did not show any significance, with P values of 0.6 and 0.8, respectively. This agreed with Long et al. [14], who found that respiratory variation in IVC diameter is moderately predictive of fluid responsiveness. A negative test cannot be used to rule out fluid responsiveness. Its clinical utility, particularly in spontaneously ventilating patients, is limited and should be interpreted in the clinical context.

These findings show our preference of FALLS-protocol in differentiating both hypovolemic and septic shock in directing fluid therapy and that we cannot depend solely on IVC diameter and collapsibility. This agreed with Corl et al. [16], who reported that a practical IVC collapsibility cutoff range in combination with clinical judgment is a reasonable alternative to a single IVC collapsibility cutoff value and might overcome variations in patient and clinical characteristics. Moreover, it agreed with the study by Orso et al. [17], in which ultrasound evaluation of the diameter of the IVC and its respiratory variations does not seem to be a reliable method to predict fluid responsiveness.

Yet, we should point to their benefit in special occasions in combination with FALLS-protocol, like we mentioned before in mixed shock.

Conclusion

LUS (FALLS-protocol) has an advantage of being a reliable, noninvasive, and simple method with rapid learning curve that can be used for differentiation and management different types of shock.

Critical care physicians should strongly consider integrating bedside chest ultrasound (FALLS-protocol) into their resuscitation pathways with a possible significant effect on patient diagnosis and management.

Recommendation

We recommend that further studies are needed to evaluate role of LUS (FALLS-protocol) in larger samples of undifferentiated shocked patients.

FALLS-protocol should be considered an easy, noninvasive, simple, and available method for differentiating types of shock and directing fluid therapy during their management.

Acknowledgements

Authors’ contributions: T.S.A.M., MD had a major role in analyzing the data and in preparing and editing the manuscript. A.A.E., MD had a major role in analyzing and interpreting the data. A.A.Y.A., MBBCh, and MSc had a major role in collecting data and writing the manuscript. O.M.M., MD had a major role in analyzing and interpreting the data. All authors have read and approved the manuscript.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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