Fluid balance and colloid osmotic pressure in acute respiratory failure: emerging clinical evidence

Available evidence suggests that both hydrostatic and osmotic forces are important in the development of acute respiratory distress syndrome (ARDS) or, more broadly, acute lung injury (ALI). More than 80% of ARDS patients in a large-scale randomized controlled trial (RCT) exhibited, at least intermittently, pulmonary artery wedge pressures (PAWP) above 18 mmHg. Retrospective analyses have shown that PAWP elevation is associated with increased mortality. Reduction in serum total protein (STP) has been shown, in a recent retrospective analysis of data from a sepsis patient population with a high frequency of ARDS, to be highly predictive of positive fluid balance, weight gain, development of ARDS, prolonged mechanical ventilation, and mortality. These findings suggest that therapy with diuretics and colloids might be of benefit in the prevention or treatment of ALI. A prospective RCT was designed and conducted to evaluate combination therapy with furosemide and albumin over a 5-day period in 37 ALI patients. Both mean serum albumin and mean STP increased promptly and substantially in furosemide + albumin recipients. The furosemide + albumin group also achieved a mean weight loss of 10 kg by the end of the treatment phase, and their weight loss exceeded that of placebo patients throughout. Hemodynamics improved in the treatment group during the 5-day protocol. Oxygenation, as assessed by the ratio between the fraction of inspired oxygen and the partial pressure of oxygen in arterial blood (PaO2/FiO2), was significantly higher within 24 h after commencement of treatment in the furosemide + albumin than the placebo group. No clinically important adverse effects of furosemide + albumin therapy were encountered. These results provide evidence that combined therapy with furosemide and albumin is effective in augmenting serum albumin and STP levels, promoting weight loss, and improving oxygenation and longer-term hemodynamic stability. Although mortality did not differ between groups, the RCT showed a trend toward reduced duration of mechanical ventilation and length of stay in the intensive care unit in patients receiving furosemide + albumin. The findings of the RCT further highlight the importance of both hydrostatic and osmotic forces in hypoxemic respiratory failure, a subject that requires further investigation.