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

Not Applicable

Interventions: Other: Passive leg raising (PLR)
Device: Echo-Doppler measurements

Brief Summary: 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.

Recruitment & Eligibility

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)

Arm && Interventions

Group	Intervention	Description
ICU intubated patients	Echo-Doppler measurements	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.
ICU intubated patients	Passive leg raising (PLR)	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.

Primary Outcome Measures

Name	Time	Method
ventricular outflow tract velocity time index (LVOT TVI)	The day of inclusion	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))

Secondary Outcome Measures

Name	Time	Method
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

Locations (1): Département d'Anesthésie-Réanimation, Hôpital Edouard Herriot,
🇫🇷
Lyon, France