Albumin kinetics, intravascular fluid volume, and respiratory function in pigs ventilated at different levels of mechanical power following crystalloid vs. albumin infusion

Authors: Simone Gattarello, Gaetano Gazzé, Emanuele Rollo, Beatrice Donati, Martina Caronna, Ilaria Grava, Carlo Chiumiento, Zhe Li, Walter Gallese, Domenico Nocera, Stefano Giovanazzi, Aurelio Sonzogni, Chiara Sonzogni, Alessandro Gatta, Francesca Collino, Luigi Camporota, Michael Quintel, Onnen Moerer, Federica Romitti, Luciano Gattinoni, & Mattia Busana.

Albumin is often used with the expectation that it increases oncotic pressure and improves tissue perfusion, yet its real impact on circulating volume remains uncertain. In this experimental study, 39 healthy female pigs were ventilated for 48 hours and received either 5% albumin or crystalloid fluids under either low- or high-mechanical-power ventilation. Despite prolonged albumin infusion, intravascular fluid volume did not differ between groups. However, animals receiving albumin lost roughly 60% of the infused albumin from the plasma, suggesting substantial redistribution outside the vascular space.

This albumin loss was accompanied by a marked increase in ascites formation compared with crystalloid-treated animals. The presence of ascites was associated with lower end-expiratory lung gas volume and higher respiratory system elastance, indicating impaired respiratory mechanics, despite histological lung injury remaining similar across groups. These findings suggest that prolonged albumin infusion may not improve circulating volume and may instead promote fluid shifts that negatively influence respiratory function.