Emergency department non-invasive cardiac output study (EDNICO): a feasibility and repeatability study

Use and Implications of Echocardiography in the Hemodynamic Assessment of Cardiogenic Shock

Cardiogenic shock (CS) is a complex multisystem syndrome due to pump failure, associated with high mortality and morbidity. Its hemodynamic characterization is key to the diagnostic algorithm and management. Pulmonary artery catheterization is the gold standard for the left and right hemodynamic evaluation, but some concerns exist for invasivity and untoward mechanical and infective complications. Transthoracic echocardiography is a robust noninvasive diagnostic tool for hemodynamic multiparametric assessment that well applies to the management of CS. Its applications expand from etiology definition to the choice of therapeutic intervention and their monitoring. The present review aims at detailing the role of ultrasounds in CS emphasizing the clinical implications of combining cardiac and non-cardiac ultrasounds examinations that may correlate with prognosis.

Simultaneous venous-arterial Doppler during preload augmentation: illustrating the Doppler Starling curve

Providing intravenous (IV) fluids to a patient with signs or symptoms of hypoperfusion is common. However, evaluating the IV fluid 'dose-response' curve of the heart is elusive. Two patients were studied in the emergency department with a wireless, wearable Doppler ultrasound system. Change in the common carotid arterial and internal jugular Doppler spectrograms were simultaneously obtained as surrogates of left ventricular stroke volume (SV) and central venous pressure (CVP), respectively. Both patients initially had low CVP jugular venous Doppler spectrograms. With preload augmentation, only one patient had arterial Doppler measures indicative of significant SV augmentation (i.e., 'fluid responsive'). The other patient manifested diminishing arterial response, suggesting depressed SV (i.e., 'fluid unresponsive') with evidence of ventricular asynchrony. In this short communication, we describe how a wireless, wearable Doppler ultrasound simultaneously tracks surrogates of cardiac preload and output within a 'Doppler Starling curve' framework; implications for IV fluid dosing are discussed.

Velocity Time Integral: A Novel Method for Assessing Fetal Anemia

The velocity time integral (VTI) is a clinical Doppler ultrasound measurement of blood flow, measured by the area under the wave curve and equivalent to the distance traveled by the blood. This retrospective study assessed the middle cerebral artery (MCA) VTI of fetuses in pregnancies complicated by maternal alloimmunization. Doppler indices of the MCA were retrieved from electronic medical records. Systolic deceleration-diastolic time, systolic acceleration time, VTI, and peak systolic velocity (PSV) were measured at 16-40 weeks gestation. Cases with PSV indicating fetal anemia (cutoff 1.5 MoM) and normal PSV were compared. The study included 255 Doppler ultrasound examinations. Of these, 41 were at 16-24 weeks (group A), 100 were at 25-32 weeks (group B), and 114 were at 33-40 weeks (group C). VTI increased throughout gestation (5.5 cm, 8.6 cm, and 12.1 cm in groups A, B, and C, respectively, p = 0.003). VTI was higher in waveforms calculated to have MCA-PSV ≥ 1.5 MoM compared to those with MCA-PSV < 1.5 MoM (9.1 cm vs. 14.1 cm, respectively, p < 0.001), as was VTI/s (22.04 cm/s vs. 33.75 cm/s, respectively; p < 0.001). The results indicate that the MCA VTI increases significantly among fetuses with suspected anemia, indicating higher perfusion of hemodiluted blood to the brain. This feasible measurement might provide a novel additional marker for the development of fetal anemia.

Intra-and inter-observer variability of point of care ultrasound measurements to evaluate hemodynamic parameters in healthy volunteers

BACKGROUND

Point-of-care ultrasound (POCUS) is a valuable tool for assessing the hemodynamic status of acute patients. Even though POCUS often uses a qualitative approach, quantitative measurements have potential advantages in evaluating hemodynamic status. Several quantitative ultrasound parameters can be used to assess the hemodynamic status and cardiac function. However, only limited data on the feasibility and reliability of the quantitative hemodynamic measurements in the point-of-care setting are available. This study investigated the intra- and inter-observer variability of PoCUS measurements of quantitative hemodynamic parameters in healthy volunteers.

METHODS

In this prospective observational study, three sonographers performed three repeated measurements of eight different hemodynamic parameters in healthy subjects. An expert panel of two experienced sonographers evaluated the images' quality. The repeatability (intra-observer variability) was determined by calculating the coefficient of variation (CV) between the separate measurements for each observer. The reproducibility (inter-observer variability) was assessed by determining the intra-class correlation coefficient (ICC).

RESULTS

32 subjects were included in this study, on whom, in total, 1502 images were obtained for analysis. All parameters were in a normal physiological range. Stroke volume (SV), cardiac output (CO), and inferior vena cava diameter (IVC-D) showed high repeatability (CV under 10%) and substantial reproducibility (ICC 0.61-0.80). The other parameters had only moderate repeatability and reproducibility.

CONCLUSIONS

We demonstrated good inter-observer reproducibility and good intra-observer repeatability for CO, SV and IVC-D taken in healthy subjects by emergency care physicians.

ARTERIAL DIAMETER VARIATIONS AS A NEW INDEX FOR STROKE VOLUME ASSESSMENT: AN EXPERIMENTAL STUDY ON A CONTROLLED HEMORRHAGIC SHOCK MODEL IN PIGLETS

ABSTRACT

Background: The assessment of cardiac output (CO) is a major challenge during shock. The criterion standard for CO evaluation is transpulmonary thermodilution, which is an invasive technique. Speckle tracking is an automatized method of analyzing tissue motion using echography. This tool can be used to monitor pulsed arterial diameter variations with low interobserver variability. An experimental model of controlled hemorrhagic shock allows for multiple CO variations. The main aim of this study is to show the correlation between the femoral arterial diameter variations (fADVs) and the stroke volume (SV) measured by thermodilution during hemorrhagic shock management and the resuscitation of anesthetized piglets. The secondary objective is to explore the respective correlations between SV and subaortic time-velocity index, abdominal aorta ADV, carotid ADV, and subclavian ADV. Methods : Piglets were bled until mean arterial pressure reached 40 mm Hg. Controlled hemorrhage was maintained for 30 minutes before randomizing the piglets to three resuscitation groups-the fluid-filling group (reanimated with saline solution only), NEph group (norepinephrine + saline solution), and Eph group (epinephrin + saline solution). Speckle tracking, echocardiographic, and hemodynamic measures were performed at different stages of the protocol. Results : Thirteen piglets were recruited and included for statistical analysis. Of all the piglets, 164 fADV measures were attempted and 160 were successful (98%). The correlation coefficient between fADV and SV was 0.71 (95% confidence interval [CI], 0.62 to 0.78; P < 0.01). The correlation coefficient between SV and abdominal aorta ADV, subclavian ADV, and carotid ADV was 0.30 (95% CI, 0.13 to 0.46; P < 0.01), 0.56 (95% CI, 0.45 to 0.66, P < 0.01), and 0.15 (95% CI, -0.01 to 0.30, P = 0.06), respectively. Conclusions : In this hemorrhagic shock model using piglets, fADV was strongly correlated with SV.

Carotid Doppler ultrasound for non-invasive haemodynamic monitoring: a narrative review

Objective.Accurate haemodynamic monitoring is the cornerstone in the management of critically ill patients. It guides the optimization of tissue and organ perfusion in order to prevent multiple organ failure. In the past decades, carotid Doppler ultrasound (CDU) has been explored as a non-invasive alternative for long-established invasive haemodynamic monitoring techniques. Considering the large heterogeneity in reported studies, we conducted a review of the literature to clarify the current status of CDU as a haemodynamic monitoring tool.Approach.In this article, firstly an overview is given of the equipment and workflow required to perform a CDU exam in clinical practice, the limitations and technical challenges potentially faced by the CDU sonographer, and the cerebrovascular mechanisms that may influence CDU measurement outcomes. The following chapter describes alternative techniques for non-invasive haemodynamic monitoring, detailing advantages and limitations compared to CDU. Next, a comprehensive review of the literature regarding the use of CDU for haemodynamic monitoring is presented. Furthermore, feasibility aspects, training requirements and technical developments of CDU are addressed.Main results.Based on the outcomes of these studies, we assess the applicability of CDU-derived parameters within three clinical domains (cardiac output, volume status, and fluid responsiveness), and amongst different patient groups. Finally, recommendations are provided to improve the quality and standardization of future research and clinical practice in this field.Significance.Although CDU is not yet interchangeable with invasive 'gold standard' cardiac output monitoring, the present work shows that certain CDU-derived parameters prove promising in the context of functional haemodynamic monitoring.

Measuring the accuracy of cardiac output using POCUS: the introduction of artificial intelligence into routine care

Background

Shock management requires quick and reliable means to monitor the hemodynamic effects of fluid resuscitation. Point-of-care ultrasound (POCUS) is a relatively quick and non-invasive imaging technique capable of capturing cardiac output (CO) variations in acute settings. However, POCUS is plagued by variable operator skill and interpretation. Artificial intelligence may assist healthcare professionals obtain more objective and precise measurements during ultrasound imaging, thus increasing usability among users with varying experience. In this feasibility study, we compared the performance of novice POCUS users in measuring CO with manual techniques to a novel automation-assisted technique that provides real-time feedback to correct image acquisition for optimal aortic outflow velocity measurement.

Methods

28 junior critical care trainees with limited experience in POCUS performed manual and automation-assisted CO measurements on a single healthy volunteer. CO measurements were obtained using left ventricular outflow tract (LVOT) velocity time integral (VTI) and LVOT diameter. Measurements obtained by study subjects were compared to those taken by board-certified echocardiographers. Comparative analyses were performed using Spearman’s rank correlation and Bland–Altman matched-pairs analysis.

Results

Adequate image acquisition was 100% feasible. The correlation between manual and automated VTI values was not significant (p = 0.11) and means from both groups underestimated the mean values obtained by board-certified echocardiographers. Automated measurements of VTI in the trainee cohort were found to have more reproducibility, narrower measurement range (6.2 vs. 10.3 cm), and reduced standard deviation (1.98 vs. 2.33 cm) compared to manual measurements. The coefficient of variation across raters was 11.5%, 13.6% and 15.4% for board-certified echocardiographers, automated, and manual VTI tracing, respectively.

Conclusions

Our study demonstrates that novel automation-assisted VTI is feasible and can decrease variability while increasing precision in CO measurement. These results support the use of artificial intelligence-augmented image acquisition in routine critical care ultrasound and may have a role for evaluating the response of CO to hemodynamic interventions. Further investigations into artificial intelligence-assisted ultrasound systems in clinical settings are warranted.

Artificial intelligence (AI) versus expert: A comparison of left ventricular outflow tract velocity time integral (LVOT-VTI) assessment between ICU doctors and an AI tool

PURPOSE

The application of point of care ultrasound (PoCUS) in medical education is a relatively new course. There are still great differences in the existence, quantity, provision, and depth of bedside ultrasound education. The left ventricular outflow tract velocity time integral (LVOT-VTI) has been successfully used in several studies as a parameter for hemodynamic management of critically ill patients, especially in the evaluation of fluid responsiveness. While LVOT-VTI has been broadly used, valuable applications using artificial intelligence (AI) in PoCUS is still limited. We aimed to identify the degree of correlation between auto LVOT-VTI and the manual LVOT-VTI acquired by PoCUS trained ICU doctors.

METHODS

Among the 58 ICU doctors who attended PoCUS training from 1 September 2019 to 30 November 2020, 46 ICU doctors who trained for more than 3 months were enrolled. At the end of PoCUS training, each of the enrolled ICU doctors acquired echocardiography parameters of a new ICU patient in 2 h after new patient was admitted. One of the two bedside expert sonographers would take standard echocardiogram of new ICU patients within 24 h. For ICU doctors, manual LVOT-VTI was obtained for reference and auto LVOT-VTI was calculated instantly by using an AI software tool. Based on the image quality of the auto LVOT-VTI, ICU patients was separated into ideal group (n = 31) and average group (n = 15).

RESULTS

Left ventricular end-diastolic dimension (LVEDd, p = 0.1028), left ventricular ejection fraction (LVEF, p = 0.3251), left atrial dimension (LA-d, p = 0.0962), left ventricular E/A ratio (p = 0.160), left ventricular wall motion (p = 0.317) and pericardial effusion (p = 1) had no significant difference between trained ICU doctors and expert sonographer. ICU patients in average group had greater sequential organ failure assessment (SOFA) score (7.33 ± 1.58 vs. 4.09 ± 0.57, p = 0.022) and lactic acid (3.67 ± 0.86 mmol/L vs. 1.46 ± 0.12 mmol/L, p = 0.0009) with greater value of LVEDd (51.93 ± 1.07 vs. 47.57 ± 0.89, p = 0.0053), LA-d (39.06 ± 1.47 vs. 35.22 ± 0.98, p = 0.0334) and percentage of decreased wall motion (p = 0.0166) than ideal group. There were no significant differences of δLVOT-VTI (|manual LVOT-VTI - auto LVOT-VTI|/manual VTI*100%) between the two groups (8.8% ± 1.3% vs. 10% ± 2%, p = 0.6517). Statistically, significant correlations between manual LVOT-VTI and auto LVOT-VTI were present in the ideal group (R2  = 0.815, p = 0.00) and average group (R2  = 0.741, p = 0.00).

CONCLUSIONS

ICU doctors could achieve the satisfied level of expertise as expert sonographers after 3 months of PoCUS training. Nearly two thirds of the enrolled ICU doctors could obtain the ideal view and one third of them could acquire the average view. ICU patients with higher SOFA scores and lactic acid were less likely to acquire the ideal view. Manual and auto LVOT-VTI had statistically significant agreement in both ideal and average groups. Auto LVOT-VTI in ideal view was more relevant with the manual LVOT-VTI than the average view. AI might provide real-time guidance among novice operators who lack expertise to acquire the ideal standard view.

Left Ventricle Outflow Tract Velocity-Time Index and Right Ventricle to Left Ventricle Ratio as Predictors for in Hospital Outcome in Intermediate-Risk Pulmonary Embolism

Accurate estimation of risk with both imaging and biochemical parameters in intermediate risk pulmonary embolism (PE) remains challenging. The aim of the study was to evaluate echocardiographic parameters that reflect right and left heart hemodynamic as predictors of adverse events in intermediate risk PE. This was a retrospective observational study on patients with computed tomography pulmonary angiography diagnosis of PE admitted at Cardiology department of the Clinical Emergency Hospital of Oradea, Romania between January 2018—December 2021. Echocardiographic parameters obtained at admission were studied as predictors of in hospital adverse events. The following adverse outcomes were registered: death, resuscitated cardiac arrest, hemodynamic deterioration and need of rescue thrombolysis. An adverse outcome was present in 50 patients (12.62%). PE related death was registered in 17 patients (4.3%), resuscitated cardiac arrest occurred in 6 patients (1.51%). Another 20 patients (5.05%) required escalation of therapy with thrombolysis and 7 (1.76%) patients developed haemodynamic instability. Echocardiographic independent predictors for in hospital adverse outcome were RV/LV ≥ 1 (HR = 3.599, 95% CI 1.378−9.400, p = 0.009) and VTI ≤ 15 mm (HR = 11.711, 95% CI 4.336−31.633, p < 0.001). The receiver operator curve renders an area under curve for LVOT VTI ≤ 15 mm of 0.792 (95% CI 0.719−0.864, p < 0.001) and for a RV/LV ≥ 1 of 0.746 (95% CI 0.671−0.821, p < 0.001). A combined criterion (LVOT VTI ≤ 15 and RV/LV ≥ 1) showed a positive predictive value of 75% and a negative predictive value of 95% regarding in hospital adverse outcomes. Low LVOT VTI and increased RV/LV are useful for identifying normotensive patients with PE at risk for short term adverse outcomes. Combining an LVOT VTI ≤ 15 cm with a RV/LV ≥ 1 can identify with increased accuracy PE patients with impending risk of clinical deterioration.

Respiratory Variations in Peak Peripheral Artery Velocities and Waveforms for Rapid Assessment of Fluid Responsiveness in Traumatic Shock Patients

Background

This study aimed to assess the correlation between the variability of the end-inspiratory and end-expiratory blood flow waveform and fluid responsiveness (FR) in traumatic shock patients who underwent mechanical ventilation by evaluating peripheral arterial blood flow parameters.

Material/Methods

A cohort of 60 patients with traumatic shock requiring mechanical ventilation-controlled breathing received ultrasound examinations to assess the velocity of carotid artery (CA), femoral artery (FA) and brachial artery (BA). A rehydration test was performed in which of 250 mL of 0.9% saline was administered within 30 min between the first and second measurement of cardiac output by echocardiography. Then, all patients were divided into 2 groups, a responsive group (FR+) and a non-responsive group (FR−). The velocity of end-inspiratory and end-expiratory peripheral arterial blood flow of all patients was ultrasonically measured, and the variability were measured between end-inspiratory and end-expiratory.

Results

The changes in the end-inspiratory and end-expiratory carotid artery blood flow velocity waveforms of the FR+ groups were significantly different from those of the FR− group (P<0.001). A statistically significant difference in ΔVmax (CA), ΔVmax (BA), and ΔVmax (FA) between these 2 groups was found (all P<0.001). The ROC curve showed that ΔVmax (CA) and ΔVmax (BA) were more sensitive values to predict FR compared to ΔVmax (FA). The sensitivity of ΔVmax (CA), ΔVmax (FA), and ΔVmax (BA) was 70.0%, 86.7%, and 93.3%, respectively.

Conclusions

The study showed that periodic velocity waveform changes in the end-inspiratory and end-expiratory peripheral arterial blood flow can be used for quick assessment of fluid responsiveness.

Rationale for using the velocity-time integral and the minute distance for assessing the stroke volume and cardiac output in point-of-care settings

Background

Stroke volume (SV) and cardiac output (CO) are basic hemodynamic parameters which aid in targeting organ perfusion and oxygen delivery in critically ill patients with hemodynamic instability. While there are several methods for obtaining this data, the use of transthoracic echocardiography (TTE) is gaining acceptance among intensivists and emergency physicians. With TTE, there are several points that practitioners should consider to make estimations of the SV/CO as simplest as possible and avoid confounders.

Main body

With TTE, the SV is usually obtained as the product of the left ventricular outflow tract (LVOT) cross-sectional area (CSA) by the LVOT velocity–time integral (LVOT VTI); the CO results as the product of the SV and the heart rate (HR). However, there are important drawbacks, especially when obtaining the LVOT CSA and thus the impaction in the calculated SV and CO. Given that the LVOT CSA is constant, any change in the SV and CO is highly dependent on variations in the LVOT VTI; the HR contributes to CO as well. Therefore, the LVOT VTI aids in monitoring the SV without the need to calculate the LVOT CSA; the minute distance (i.e., SV × HR) aids in monitoring the CO. This approach is useful for ongoing assessment of the CO status and the patient’s response to interventions, such as fluid challenges or inotropic stimulation. When the LVOT VTI is not accurate or cannot be obtained, the mitral valve or right ventricular outflow tract VTI can also be used in the same fashion as LVOT VTI. Besides its pivotal role in hemodynamic monitoring, the LVOT VTI has been shown to predict outcomes in selected populations, such as in patients with acute decompensated HF and pulmonary embolism, where a low LVOT VTI is associated with a worse prognosis.

Conclusion

The VTI and minute distance are simple, feasible and reproducible measurements to serially track the SV and CO and thus their high value in the hemodynamic monitoring of critically ill patients in point-of-care settings. In addition, the LVOT VTI is able to predict outcomes in selected populations.

Emergency department non-invasive cardiac output study (EDNICO): an accuracy study

BACKGROUND

There is little published data investigating non-invasive cardiac output monitoring in the emergency department (ED). We assess here the accuracy of five non-invasive methods in detecting fluid responsiveness in the ED: (1) common carotid artery blood flow, (2) suprasternal aortic Doppler, (3) bioreactance, (4) plethysmography with digital vascular unloading method, and (5) inferior vena cava collapsibility index. Left ventricular outflow tract echocardiography derived velocity time integral is the reference standard. This follows an assessment of feasibility and repeatability of these methods in the same cohort of ED patients.

METHODS

This is a prospective observational study of non-invasive methods for assessing fluid responsiveness in the ED. Participants were non-ventilated ED adult patients requiring intravenous fluid resuscitation. Sensitivity and specificity of each method in determining the fluid responsiveness status of participants is determined in comparison to the reference standard.

RESULTS

Thirty-three patient data sets were included for analysis. The specificity and sensitivity to detect fluid responders was 46.2 and 45% for common carotid artery blood flow (CCABF), 61.5 and 63.2% for suprasternal artery Doppler (SSAD), 46.2 and 50% for bioreactance, 50 and 41.2% for plethysmography vascular unloading technique (PVUT), and 63.6 and 47.4% for inferior vena cava collapsibility index (IVCCI), respectively. Analysis of agreement with Cohen's Kappa - 0.08 for CCABF, 0.24 for SSAD, - 0.04 for bioreactance, - 0.08 for PVUT, and 0.1 for IVCCI.

CONCLUSION

In this study, non-invasive methods were not found to reliably identify fluid responders. Non-invasive methods of identifying fluid responders are likely to play a key role in improving patient outcome in the ED in fluid depleted states such as sepsis. These results have implications for future studies assessing the accuracy of such methods.