Impact of Fluid Resuscitation Therapy on Pulmonary Edema as Measured by Alveolar Fluid Clearance in Patients With Acute Respiratory Distress Syndrome (ARDS)

The need for fluid resuscitation (FR) in ICU patients with acute respiratory distress syndrome (ARDS) is common. Indeed, relative or absolute hypovolemia is a common phenomenon that the intensivist must recognize early and treat promptly. Fluid challenge may have adverse side effects associated with fluid administration. The diffusion within the interstitial space may favor edema formation and cause cardiac dysfunction by volume overload. Edema formation is global and may specifically alter pulmonary alveolar epithelial integrity, leading to enhanced alveolar edema and impaired gas exchange. Currently, two types of fluids are frequently used, crystalloids and colloids. Among colloids and compared to crystalloids, albumin has the theoretical advantage of causing greater volume expansion. We hypothesized that a fluid resuscitation therapy with albumin generates less pulmonary edema than a fluid resuscitation therapy with crystalloids. The aim of our study is to compare alveolar fluid clearance, as a marker of alveolar edema fluid resorption, in 2 groups of patients: those treated with albumin and those treated with crystalloid.

The main objective of our prospective double blind, randomized, controlled trial is to compare the rate of alveolar fluid clearance, a marker of alveolar edema fluid resorption, in 2 groups of patients with ARDS and suffering from hypovolemia: those treated with albumin and those treated with crystalloid (fluid challenge of 7 mL/kg over 15 minutes, that can be repeated 3 times if hypovolemia persists). The evolution of respiratory and hemodynamic parameters, as measured by transpulmonary thermodilution (extra-vascular lung water, pulmonary vascular permeability index, cardiac output, global enddiastolic volume), plasma osmolality, plasma oncotic pressure and plasma levels of brain natriuretic peptid (BNP) will be studied one hour and 3 hours after after fluid resuscitation in the two groups. In order to evaluate alveolar epithelial dysfunction in patients receiving either albumin or crystalloid, plasma and alveolar levels of sRAGE (the soluble form of the receptor for advanced glycation endproducts) will be measured by ELISA. Lung aeration and fluid-induced derecruitment will be evaluated with an electrical impedance tomograph (PulmoVista®500, Dräger).