Abstract
IntroductionThe study was designed to assess the impact of fluid loading on lung aeration, oxygenation and hemodynamics in patients with septic shock and acute respiratory distress syndrome (ARDS).MethodsDuring a 1-year period, a prospective observational study was performed in 32 patients with septic shock and ARDS. Cardiorespiratory parameters were measured using Swan Ganz (n = 29) or PiCCO catheters (n = 3). Lung aeration and regional pulmonary blood flows were measured using bedside transthoracic ultrasound. Measurements were performed before (T0), at the end of volume expansion (T1) and 40 minutes later (T2), consisting of 1-L of saline over 30 minutes during the first 48 h following onset of septic shock and ARDS.ResultsLung ultrasound score increased by 23% at T2, from 13 at baseline to 16 (P < 0.001). Cardiac index and cardiac filling pressures increased significantly at T1 (P < 0.001) and returned to control values at T2. The increase in lung ultrasound score was statistically correlated with fluid loading-induced increase in cardiac index and was not associated with increase in pulmonary shunt or regional pulmonary blood flow. At T1, PaO2/FiO2 significantly increased (P < 0.005) from 144 (123 to 198) to 165 (128 to 226) and returned to control values at T2, whereas lung ultrasound score continued to increase.ConclusionsEarly fluid loading transitorily improves hemodynamics and oxygenation and worsens lung aeration. Aeration changes can be detected at the bedside by transthoracic lung ultrasound, which may serve as a safeguard against excessive fluid loading.
Highlights
The study was designed to assess the impact of fluid loading on lung aeration, oxygenation and hemodynamics in patients with septic shock and acute respiratory distress syndrome (ARDS)
Fluid loading-induced aeration loss observed between T0 and T2 was mainly due to the onset of coalescent B lines in initially normally aerated lung regions or regions with interstitial edema characterized by B1 lines (Figure 1A)
The present study performed in patients with septic shock and ARDS shows that the hemodynamic benefit of fluid loading is associated with worsened lung aeration that does not match a decline in oxygenation
Summary
The study was designed to assess the impact of fluid loading on lung aeration, oxygenation and hemodynamics in patients with septic shock and acute respiratory distress syndrome (ARDS). Fluid administration may contribute to pulmonary edema in critically ill patients with acute respiratory distress syndrome (ARDS) whose alveolar-capillary permeability is increased. Because hypoxic pulmonary vasoconstriction is markedly impaired by lung and systemic inflammation [3], increase in venous mixed oxygen saturation (SvO2) may improve arterial oxygenation if pulmonary blood flow does not increase in non aerated lung regions. Interstitial-alveolar edema, lung aeration and their variations can be assessed noninvasively using bedside transthoracic lung ultrasound [5,6,7]. Changes in pulmonary blood flow supplying non aerated lung regions can be evaluated using bedside Doppler lung ultrasound [8,9,10,11]
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