Fluid Responsiveness Evaluation by a Non-invasive Method in CHildren
Condition: Circulatory Failure (Shock)
MeSH terms: Shock
Study type: Observational

Summary: 
      In this study, the investigators aim to validate a non-invasive marker of
      fluid-responsiveness in children with acute circulatory failure based on standardized
      abdominal compression. This would allow physicians to identify which patient could benefit
      from a fluid expansion, thus avoiding a potentially useless or even dangerous fluid
      expansion, leading to fluid overload. To this end, the investigators will evaluate the
      diagnostic accuracy (sensitivity and specificity) of stroke volume variation induced by
      standardized abdominal compression for the diagnosis of fluid responsiveness (based on the
      gold-standard test: significant increase in cardiac index after fluid expansion).
    

Detailed description: 
      Fluid expansion is the cornerstone of acute circulatory failure treatment in children
      Although this therapy drastically reduced mortality, several studies in recent years have
      highlighted the adverse effects of excessive fluid expansion (leading to fluid overload).
      Currently, the search for indicators to predict fluid responsiveness is a major issue in
      intensive care. These indicators are based on Franck-Starling's law: if small changes in
      preload lead to an increase in cardiac output, then fluid responsiveness can be expected.
      However, in children, the only validated indicator (respiratory variability of peak aortic
      velocity) can only be used in the absence of any spontaneous respiratory movement, a rare
      situation in practice. Recently, two pediatric studies investigated a simple clinical test:
      hepatic or abdominal compression. This clinical maneuver, by increasing venous return via
      mobilization of the hepato-splanchnic reserve, induces a transient and reversible preload
      increase. The evaluation of the hemodynamic effects of this "endogenous fluid expansion"
      allowed, according to the authors, to accurately predict fluid responsiveness. However,
      several factors reduce the applicability of these results: the small number of studies on
      this subject, the smaller volume of fluid used than in clinical practice, and the population
      studied, composed almost exclusively of children in postoperative of cardiac surgery.

      In this study, the investigators will evaluate the diagnostic accuracy of abdominal
      compression for the diagnosis of fluid responsiveness in children with acute circulatory
      failure, hospitalized in pediatric intensive care unit (PICU) for a medical or a non-cardiac
      surgical condition, for whom a fluid expansion was prescribed by the physician in charge. The
      index test will be the stroke volume variation following a standardized abdominal compression
      (before fluid expansion). The gold standard test will be the variation of cardiac output
      between baseline and after fluid expansion, a variation > 15% defining fluid responsiveness.

      In this non interventional study of diagnostic accuracy, patients will undergo an extra
      echocardiographic assessment, but no supplemental blood test or invasive parameters will be
      collected. Simple clinical parameters will be collected within 4 hours after the fluid
      expansion. Patients will be follow-up until PICU discharge.
    

Intervention name(s): Non interventional study (study of diagnostic accuracy with an extra echocardiographic assessment).
Intervention type(s): Procedure
Intervention description(s): Fluid expansion will be delayed while our index test is performed. After fluid expansion, patient will undergo an echocardiographic assessment of response to fluid expansion (gold-standard).
Our index test is the ΔSVi-AC: indexed percentage of stroke volume variation between baseline and during a standardized abdominal compression. Stroke volume will be assessed by transthoracic echocardiography.
Patient will undergo 3 echocardiographic assessment: At baseline, During abdominal compression, After the 10 to 20ml/kg crystalloid fluid expansion Abdominal compression : a sphygmomanometer will be inflated to a pressure of less than 10 mmHg and will be applied to the center of the patient's abdomen. Then, a gentle compression on the sphygmomanometer will be performed, calibrated at 22 - 26 mmHg according to the sphygmomanometer. The echocardiographic assessments will take place between 10 and 60 seconds after the start of the compression, which will therefore last less than a minute.
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        At least 24 fluid expansion are needed, in 10 to 24 patients (maximum of 3 fluid expansion
        per patient). The "number needed to treat" was calculated with Obuchowski method, with an
        aphla risk of 0.05, a statistical power of 80%, a ratio "responder/nonresponder" of 1:1,
        and a predicted area under the receiver operating characteristic curve of 0.78 (based on
        previous studies).

        In order to be clinically relevant, since a large majority of patients admitted to our PICU
        are under 2 years of age, the investigators plan to include 24 fluid expansions
        administrated to patients under 2 years old. Therefore, the investigators might include
        more than 24 fluid expansions if some are administrated to patients older than 2 years old.
        Without this correction, our study might be underpowered if age is found to be a bias in
        fluid responsiveness.
      
Keywords: shock; volume expansion; goal-directed fluid management; echocardiography