Shock is a common and serious cause of admission to intensive care. Vascular filling is one of the cornerstones of shock treatment, aimed at increasing cardiac output and restoring adequate organ perfusion through rapid intravenous administration of a solution. However, this vascular filling can be accompanied by venous congestion, which can be harmful. Fluid administration must therefore be sparing and carefully considered.

However, it is difficult to assess the correct amount of intravenous fluid to inject. Multi-site venous ultrasound (inferior vena cava, suprahepatic vein, portal vein, renal vein), recently published under a score called VExUS, could be a useful bedside tool for documenting venous congestion and avoiding excessive vascular filling. Nevertheless, this tool has been little evaluated in the general intensive care population, particularly in patients with acute respiratory distress syndrome (ARDS). Its link with other venous sites (femoral, popliteal) has also been little studied to date.

The main objective of our study is to describe the distribution of the VEXUS score among patients in a general intensive care unit.

The secondary objectives are:

• To study the feasibility of measuring the VEXUS score in patients with ARDS, including during prone positioning, a recommended and frequently used treatment for this condition, which could make it difficult to acquire venous ultrasound data.
• In this case, other more accessible venous flows could be analysed, namely the femoral venous flow and the popliteal venous flow. We will therefore also study their feasibility during prone positioning sessions.
• Subsequently, we will study the correspondence between the VEXUS score and these other types of venous flow (femoral, popliteal).
• Finally, we will evaluate the association between the VEXUS score in our general intensive care population and the long-term prognosis of patients, in this case death on day 28 and the occurrence of acute renal failure requiring renal replacement therapy during the intensive care stay.

I) SCIENTIFIC JUSTIFICATION FOR THE RESEARCH :

1. SUMMARY OF CLINICAL AND NON-CLINICAL TRIAL RESULTS :

Shock is a common cause of admission to intensive care:

By causing hypoperfusion of vital organs (kidneys, liver, digestive tract, heart), it can lead to multiple organ failure and death. There are many causes of shock, the main one being severe infection, with approximately 49 million cases worldwide each year and approximately 11 million deaths attributable to shock each year.

Vascular filling is necessary to treat shock:

The first treatment for shock is vascular filling, which consists of the intravenous administration of an isotonic solution over a short period of time. In septic shock, international guidelines recommend injection of 30 mL/kg of fluids as early as possible within the first three hours. The aim of vascular filling is to increase left ventricular systolic ejection volume, and therefore cardiac output and organ perfusion.

Excessive vascular filling is harmful:

However, vascular filling carries a risk of congestion of the venous system. This congestive state has potentially harmful adverse effects, which are now well established: intracranial hypertension and delirium, difficulties in weaning from mechanical ventilation and excess mortality in acute respiratory distress syndrome, acute renal failure, acute congestive hepatitis, intra-abdominal hypertension, decreased intestinal motility or risk of digestive ischaemia and bacterial translocation. Cardiac effects are also plausible. This explains the now well-established statistical link between positive fluid balance and excess mortality.

Fluid administration must therefore be carefully considered and sparing. With this in mind, several authors have recently proposed a concept known as R.O.S.E., which divides resuscitation into four distinct phases: a Resuscitation phase, during which vascular filling is undoubtedly necessary; an Optimisation phase, followed by a Stabilisation phase, during which fluid administration must be adjusted to maintain adequate organ perfusion while avoiding fluid overload, and a final Evacuation phase, during which any excess fluid must be eliminated through the use of diuretics or dialysis. In other words, it is a matter of finding the right window between administering an antidote and poison, to paraphrase Paracelsus. The 2021 guidelines of the Surviving Sepsis Campaign have taken this on board, suggesting that 'to avoid over- and under-resuscitation, fluid administration beyond the initial resuscitation phase should be guided by careful monitoring of volume status and organ perfusion'.

Assessing the correct amount of vascular filling to administer is difficult Multiple tests, whether static (pulse pressure variation, etc.) or dynamic (passive leg raise test), invasive (continuous cardiac output measurement) or non-invasive (echocardiography), are currently available and their results can guide the decision on whether or not to continue vascular filling. However, while this assessment is essential, it is not sufficient on its own, as congestive heart failure can coexist with preload dependence, as demonstrated in a recent study.

Venous ultrasound can detect excess vascular filling Venous congestion should therefore be assessed at the same time. As before, a wide range of tools are available for this purpose, each with its own advantages and limitations. Clinicians can take into account recent medical history, weight gain, clinical detection of oedema in the lower parts of the body, invasive measurement of central venous pressure, echocardiographic measurements, blood biomarkers, and radiological imaging of the lungs. These investigations, which are sometimes tedious, invasive, and non-dynamic, have led to the development of other tools for measuring venous congestion, such as ultrasound of the main veins: the inferior vena cava, to which the suprahepatic veins (and the portal venous system via the liver) and renal veins are connected, and the femoral veins, among others. Preliminary work has already established a link between specific patterns of these venous flows and a congestive state.

The value of venous ultrasound in detecting excessive vascular filling has been little evaluated in the general intensive care population, particularly in patients with acute respiratory distress syndrome The most comprehensive study to date combined several of these patterns (inferior vena cava, suprahepatic vein, portal vein, and renal vein) into a single score, called VEXUS (Venous EXcess Ultrasound Grading System), graded from 0 to 3. A high score was significantly associated with an increased risk of acute renal failure in the cardiac surgery population analysed. Similar results were observed after acute coronary syndrome. A single small study was conducted in the general intensive care population. This study did not specifically evaluate VEXUS in patients with acute respiratory distress syndrome (ARDS), a condition frequently encountered in intensive care. ARDS has several specific characteristics that warrant analysis of venous congestion. On the one hand, pulmonary injury warrants early detection and treatment of congestive state, a recognised risk factor for respiratory deterioration and excess mortality. On the other hand, hypoxaemia and its treatment with high-pressure positive pressure ventilation can cause acute right heart failure, worsening venous congestion. Finally, in cases of refractory hypoxaemia, prone positioning is recommended by the European Society of Intensive Care Medicine following the publication of the French PROSEVA study. The feasibility of measuring venous congestion using VEXUS in the prone position has not been evaluated. Analysis of femoral venous flow or even popliteal venous flow could be useful in this situation.

............................................................................................................................................................................................................................................................................2) SUMMARY OF EXPECTED AND KNOWN BENEFITS AND RISKS : The research procedure consists of an abdominal venous ultrasound (inferior vena cava, portal vein, suprahepatic vein and renal vein) to calculate the VEXUS score, and a venous ultrasound of the lower limbs (femoral vein and popliteal vein). This procedure will be performed at the same time as the cardiac ultrasound (using the same equipment), which is a routine examination.

This is a non-invasive, non-irradiating examination that has been proven to be safe. There are therefore no risks associated with the research.

The expected benefit is collective:

• To determine the distribution of the VEXUS score among patients in the general intensive care unit.
• To determine the feasibility of measuring the VEXUS score in the prone position.
• To determine the evolution of the VEXUS score in the prone position.
• To determine the correlation between the VEXUS score and femoral and popliteal venous flow.

In addition, the ultrasound protocol used could enable early diagnosis of venous thrombosis (suprahepatic, portal, renal, femoral or popliteal), thereby helping to improve patient care.

• 3) DESCRIPTION OF THE POPULATION TO BE STUDIED All consecutive adult patients admitted to a medical intensive care unit (Besançon Teaching Hospital, Besançon, FRANCE).
• 4) REFERENCES TO SCIENTIFIC LITERATURE: BIBLIOGRAPHY See "Citations" field in the "References" module of the record.

Inclusion Criteria:

• Patients admitted to medical intensive care at Besançon Teaching Hospital for any reason.
• Aged over 18.
• Affiliated with a French social security scheme or beneficiary of such a scheme.
• No objection to participating in the study.

Non-inclusion criteria :

• Minors
• Pregnant women and breastfeeding mothers
• Persons deprived of their liberty by judicial or administrative decision; persons undergoing compulsory psychiatric treatment; persons admitted to a health or social care institution for purposes other than research
• Adults subject to legal protection measures or unable to give their consent
• Subjects who are excluded from another study or listed in the 'national volunteer registry'.

Exclusion Criteria:

- Portal vein, suprahepatic or femoral vein thrombosis at the time of ultrasound examination.