Fluid restriction is superior in acute lung injury and ARDS
ABSTRACTRestricting fluid intake and promoting fluid excretion (a "dry" or conservative strategy) is more effective than a "we or liberal strategy in patients with acute lung injury and acute respiratory distress syndrome. In a multicenter, randomized, prospective clinical comparison of the two strategies in 1000 patients, those in the conservative-strategy group experienced faster improvement in lung function and spent significantly fewer days on ventilation and in the intensive care unit (N Engl J Med 2006; 354:2564-2574). No significant differences were observed in the incidence of death by 60 days or of nonpulmonary organ failure at 28 days except for days of central nervous system failure, which were fewer in the conservative-strategy group.
KEY POINTS
- In the conservative-strategy group, the target filling pressures were a pulmonary artery occlusion pressure less than 8 mm Hg for those with a pulmonary artery catheter and a central venous pressure less than 4 mm Hg for those with only a central venous catheter. Pressures were brought into these ranges by diuresis.
- The conservative-strategy group did not experience more frequent need for dialysis or more shock.
- Although the number of adverse events—particularly ,metabolic alkalosis and electrolyte imbalance—was significantly higher in the conservative-strategy group, the overall incidence was low.
CONCLUSION
The two fluid-management protocols used in this study were designed to be prudent yet distinctly different. While designing our protocol, we were concerned on the one hand that despite our best efforts fluid balance would turn out to be very similar in the two groups; this did not happen. On the other hand, we were also worried that the fluid level in one of the two groups might turn out to be so bizarre that it would invalidate our study; this too did not occur. Therefore, we are pleased with the way the study was designed and conducted, and we are satisfied that the two protocols were legitimate.
As we went into our study, the literature contained only one other prospective trial that was in some way similar to ours. Mitchell et al9 conducted a randomized, prospective study of 101 critically ill patients, including 89 with pulmonary edema. A group of 52 patients were managed with a conservative strategy intended to reduce the amount of extravascular lung water; the other 49 patients were managed with a strategy similar to the liberal strategy used in our study. At the study’s end, the patients in the conservative-strategy group had a significantly lower amount of extravascular lung water and spent significantly fewer days on ventilation and in the ICU. No clinically significant adverse effects were associated with the conservative strategy. This small study was not highly powered, but it did show that aggressive fluid restriction conferred some benefit.
In our study, the conservative strategy improved lung function and shortened the duration of mechanical ventilation and ICU stay without increasing nonpulmonary organ failures or increasing the risk of death within 60 days. Therefore, we recommend the conservative strategy for patients with ALI/ARDS.
