Role of Fluid and Sodium Retention in Experimental Ventilator-Induced Lung Injury
Simone Gattarello, Iacopo Pasticci, Mattia Busana, Stefano Lazzari, Paola Palermo, Maria Michela Palumbo, Federica Romitti, Irene Steinberg, Francesca Collino, Francesco Vassalli, Thomas Länger, Onnen Moerer, Leif Saager, Peter Herrmann, Paolo Cadringher, Konrad Meissner, Michael Quintel, Luciano Gattinoni
Abstract
Background: Ventilator-induced lung injury (VILI) via respiratory mechanics is deeply interwoven with hemodynamic, kidney and fluid/electrolyte changes. We aimed to assess the role of positive fluid balance in the framework of ventilation-induced lung injury. Methods: Post-hoc analysis of seventy-eight pigs invasively ventilated for 48 h with mechanical power ranging from 18 to 137 J/min and divided into two groups: high vs. low pleural pressure (10.0 ± 2.8 vs. 4.4 ± 1.5 cmH 2 O; p < 0.01). Respiratory mechanics, hemodynamics, fluid, sodium and osmotic balances, were assessed at 0, 6, 12, 24, 48 h. Sodium distribution between intracellular, extracellular and non-osmotic sodium storage compartments was estimated assuming osmotic equilibrium. Lung weight, wet-to-dry ratios of lung, kidney, liver, bowel and muscle were measured at the end of the experiment. Results: High pleural pressure group had significant higher cardiac output (2.96 ± 0.92 vs. 3.41 ± 1.68 L/min; p < 0.01), use of norepinephrine/epinephrine (1.76 ± 3.31 vs. 5.79 ± 9.69 mcg/kg; p < 0.01) and total fluid infusions (3.06 ± 2.32 vs. 4.04 ± 3.04 L; p < 0.01). This hemodynamic status was associated with significantly increased sodium and fluid retention (at 48 h, respectively, 601.3 ± 334.7 vs. 1073.2 ± 525.9 mmol, p < 0.01; and 2.99 ± 2.54 vs. 6.66 ± 3.87 L, p < 0.01). Ten percent of the infused sodium was stored in an osmotically inactive compartment. Increasing fluid and sodium retention was positively associated with lung-weight ( R 2 = 0.43, p < 0.01; R 2 = 0.48, p < 0.01) and with wet-to-dry ratio of the lungs ( R 2 = 0.14, p < 0.01; R 2 = 0.18, p < 0.01) and kidneys ( R 2 = 0.11, p = 0.02; R 2 = 0.12, p = 0.01). Conclusion: Increased mechanical power and pleural pressures dictated an increase in hemodynamic support resulting in proportionally increased sodium and fluid retention and pulmonary edema.