Transthoracic Echocardiography of the Superior Vena Cava in Intensive Care Units (ICU) Intubated Patients

Study Overview
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Brief Summary
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Acute circulatory failure is frequent, affecting up to one-third of patients admitted to intensive care units (ICU). Monitoring hemodynamics and cardiac function is therefore a major concern. Analysis of respiratory diameter variations of the superior vena cava (SVC) is easily obtained with transesophageal echocardiography (TEE) and is helpful to assess fluid responsiveness. Transthoracic echocardiography (TTE) exploration of the SVC is not used in routine. Recently, micro-convex ultrasound transducers have been marketed and these may be of use for non-invasive SVC flow examination. However, analysis of diameter variations of the SVC with TTE does not seem to be possible since the approach from the supraclavicular fossa does not allow for a good visualization of the SVC walls. It was recently demonstrated in a short pilot study that TTE examination of the SVC flow with a micro-convex ultrasound transducer (GE 8C-RS) seems both easy to learn and to use (feasibility = 84.9%), and is reproducible in most ventilated ICU patients with an intraclass correlation coefficient for the systolic fraction of the superior vena cava flow of 0.90 (95% confidence interval [0.86-0.93]). The hypothesis is that cardio-respiratory interactions in intubated-ventilated patients are responsible of SVC flow variations and that the analysis of the SVC flow respiratory variations could be a new predictive tool of fluid responsiveness.

Official Title
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Transthoracic Echocardiographic Assessment of the Superior Vena Cava Flow Respiratory Variation in ICU Intubated Patients

Conditions
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Intubated Patients, Admission in Intensive Care Unit

Intervention / Treatment
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* Other: Passive leg raising (PLR)
* Device: Echo-Doppler measurements


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult patients (≥ 18 years old) Admission in ICU after tracheal intubation or tracheal intubation during the ICU stay Volume-controlled ventilation with a tidal volume of 8 mL/kg Patient or family agreement for the inclusion Exclusion Criteria: Persistence of spontaneous breathing Cardiac arrhythmia Severe Acute Respiratory Distress Syndrome, defined as PaO2/FIO2 ratio < 100 Acute right ventricular failure defined by S'VD < 10 cm or Tricuspid Annular Plane Systolic Excursion (TAPSE) < 10 mm measured with Transthoracic Echocardiography (TTE)

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: ICU intubated patients<br>After inclusion, Echo-Doppler measurements are performed with Vivid S6 model (GE Healthcare France, Lyon, France). The left ventricular outflow tract velocity time index (LVOT TVI) will be measured with this device. Then, a passive leg raising (PLR) will be performed and finally LVOT VTI will be measured again after PLR Patients will be classified in two groups according to the hemodynamic response to PLR : Patients are responders if LVOT VTI increases of at least 10% after PLR patients are non-responders if LVOT VTI does not increase or increase of less than 10% after PLR. | Other: Passive leg raising (PLR)<br>* PLR is a test that predicts whether cardiac output will increase with volume expansion. By transferring a volume of around 300 mL of venous blood from the lower body toward the right heart, PLR mimics a fluid challenge. However, no fluid is infused and the hemodynamic effects are rapidly reversible, thereby avoiding the risks of fluid overload. PLR starts from the semi-recumbent and not the supine position. PLR is performed by adjusting the bed and not by manually raising the patient's legs<br>Device: Echo-Doppler measurements<br>* Echo-Doppler measurements are performed with Vivid S6 model (GE Healthcare France, Lyon, France). All measurements are recorded at the end of expiration. Echo-Doppler measurements are performed in the upper part of the SVC, approximately 1 to 2 cm below the brachiocephalic vein. From this view, pulse Doppler is performed. Pulse Doppler waves obtained in the SVC are used to obtain velocity time integrals (VTI). Expiratory VTI is named VTImax and inspiratory VTI is named VTImin. These values will allow the calculation of Respiratory variations of the superior vena cava flow (ΔSVCf). ΔSVCf is calculated as (VTImax- VTImin )/(1/2(VTImax+ VTImin)).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| ventricular outflow tract velocity time index (LVOT TVI) | Echo-Doppler measurements are performed with Vivid S6 model (GE Healthcare France, Lyon, France). All measurements are recorded at the end of expiration. Echo-Doppler measurements are performed in the upper part of the SVC, approximately 1 to 2 cm below the brachiocephalic vein. From this view, pulse Doppler is performed. Pulse Doppler waves obtained in the SVC are used to obtain velocity time integrals (VTI). Expiratory VTI is named VTImax and inspiratory VTI is named VTImin. These values will allow the calculation of Respiratory variations of the superior vena cava flow (ΔSVCf). ΔSVCf is calculated as(VTImax- VTImin )/(1/2(VTImax+ VTImin)) | The day of inclusion | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| optimal cut-off value of ΔSVCf to predict fluid-responsiveness |  | The day of inclusion | 
| proportion of patients in which measurement of ΔSVCf is not possible |  | The day of inclusion | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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superior vena cava