First do no harm: surrogate endpoints and the lesson of β-agonists in acute lung injury

Abstract

Background: β2-adrenergic receptor agonists accelerate resolution of pulmonary edema in experimental and clinical studies of acute lung injury (ALI).

Methods: Objective: To determine whether an aerosolized β2-agonist would improve clinical outcomes in patients with ALI. Design: Multi-center, phase III randomized, placebo-controlled clinical trial. Setting: 33 hospitals participating National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network. Subjects: Patients who were intubated and receiving mechanical ventilation, had bilateral infiltrates consistent with edema on frontal chest radiograph, had a ratio of PaO2 to FIO2 (fraction of inspired oxygen) of 300 or less, and not had clinical evidence of left atrial hypertension. A maximum enrolment of 1,000 patients was planned. Intervention: Patients were randomized to receive aerosolized albuterol (5 mg) or saline placebo every 4 hours for up to 10 days. Outcomes: The primary outcome variable was ventilator-free days (VFD). Secondary outcome measures included mortality before hospital discharge on day 60 and day 90, the number of intensive care unit (ICU)-free days and the number of organ failure-free days.

Results: There were 282 patients enrolled before the trial was stopped for futility after the second interim analysis. The VFDs difference with albuterol treatment was unfavourable by -2.2 days, well past the futility boundary of -0.4 VFDs. VFDs were not significantly different between the albuterol and placebo groups (means of 14.4 and 16.6 days, respectively; 95% confidence interval for the difference, -4.7 to 0.3 days; P = 0.087). Rates of death before hospital discharge and the number of organ failure-free days were also not significantly different between the two groups. The number of ICU-free days was lower in the albuterol group in comparison with the placebo group (means of 13.5 and 16.2 days respectively; 95% confidence intervals for the mean difference, -4.9 to -0.4 days; P = 0.023). Overall, heart rates were significantly higher in the albuterol group by approximately 5 beats/minute in the first 2 days after randomization (P < 0.05), but rates of new onset atrial fibrillation (10% in both groups) and other cardiac dysrhythmias were not significantly different.

Conclusions: These results suggest that aerosolized albuterol does not improve clinical outcomes in ALI patients. Routine use of β2 agonist therapy in mechanically ventilated ALI patients cannot be recommended.