Although most clinicians tend to manage acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) by giving more rather than less fluid,1,2 patients may actually fare better under a strategy of limited fluid intake and increased fluid excretion.
According to the results of the Fluids and Catheters Treatment Trial (FACTT),3 patients managed with fluid restriction (the “dry” or conservative strategy) spent significantly less time in the intensive care unit (ICU) and on mechanical ventilation than did patients who received a high fluid intake (the “wet” or liberal strategy). These benefits of the conservative strategy were attained without any increase in the mortality rate at 60 days or in nonpulmonary organ failure at 28 days.
In this article, I discuss the basis for the FACTT researchers’ conclusion that a conservative fluid strategy is preferable to a liberal fluid strategy in ALI/ARDS.
One of the more enduring questions in critical care medicine is which fluid-management strategy is best for patients with ALI/ARDS.
The conservative strategy results in a lower vascular filling pressure, which in turn reduces pulmonary edema and improves gas exchange. The drawback to this strategy is that it may have a negative effect on cardiac output and nonpulmonary organ function.
The liberal strategy results in a higher vascular filling pressure, which may be beneficial in terms of cardiac output and nonpulmonary organ perfusion. However, this strategy does not reduce lung edema.
The evidence accumulated before FACTT did not favor one strategy over the other. However, most deaths among patients with ALI/ARDS are attributable to the failure of organs other than the lungs.4,5 As a result, aggressive fluid restriction has not been a common approach in hospitals throughout the United States.1,2
In an effort to resolve the controversy surrounding the management of ALI/ARDS and to broaden the scope of what we know about fluid balance, we undertook this multicenter, randomized, prospective clinical comparison of the two strategies. This study was conducted under the auspices of the National Heart, Lung, and Blood Institute’s Acute Respiratory Distress Syndrome Clinical Trials Network (ARDSnet).
Between June 8, 2000, and October 3, 2005, we screened more than 11,000 patients with ALI/ARDS at 20 centers in North America.
Eligible patients had experienced ALI/ARDS within the previous 48 hours, had been intubated for positive-pressure ventilation, had a ratio of partial pressure of arterial oxygen (PaO2) to the fraction of inspired oxygen (FIO2) of less than 300, and exhibited bilateral infiltrates on chest radiography that were consistent with the presence of pulmonary edema without evidence of left atrial hypertension.6
Major exclusion criteria included the placement of a pulmonary artery catheter prior to randomization and the presence of certain illnesses that might have compromised the study results.
The target enrollment of 1,000 patients was reached. These patients were randomized into one of four roughly equal groups based on the type of fluid-management strategy—conservative or liberal—and the type of catheter that was placed—pulmonary artery or central venous. (The ARDSnet researchers published the results of the catheter comparison in a separate article.7 Those results are not discussed here except to note that there were no statistically significant differences in outcomes between the two catheter groups.)
There were no statistically significant differences between the two groups with respect to baseline demographic characteristics. The conservative-strategy group consisted of 503 patients, of whom 52% were male and 65% were white; the mean age was 50.1 years. The liberal-strategy group consisted of 497 patients, of whom 55% were male and 63% were white; mean age was 49.5 years.