Effects of early administration of acetazolamide on the duration of mechanical ventilation in patients with chronic obstructive pulmonary disease or obesity-hypoventilation syndrome with metabolic alkalosis. A randomized trial.

BACKGROUND: Metabolic alkalosis (MA) inhibits respiratory drive and may delay weaning from mechanical ventilation (MV). MA is common in CO2 -retainer patients that need MV. Acetazolamide (ACTZ) decreases serum bicarbonate concentration and stimulates respiratory drive. This study evaluated the effects of ACTZ on the duration of MV in patients with MA and COPD or obesity hypoventilation syndrome (OHS) intubated with acute respiratory failure.

METHODS: Multicenter, randomized, controlled, double-blind study, with COPD or OHS patients with MV < 72 h and initial bicarbonate >28 mmol/L and pH > 7.35. Test-treatment, ACTZ 500 mg or placebo, was daily administered if pH > 7.35 and bicarbonate >26 mmol/L. Clinical, respiratory and laboratory parameters were recorded.

RESULTS: 47 patients (36 men) were randomized. There were no significant differences between groups in comorbidities, baseline characteristics or arterial blood gases at inclusion. The mean difference in the duration of MV between placebo and ACTZ group was 1.3 days (95%CI, -2.1-4.8; p = 0.44). Kaplan-Meier curves showed no differences in the duration of MV (Log-Rank p = 0.41). Between-group comparison of estimated marginal means (CI 95%) during MV were, respectively: PaCO2 55 (51-59) vs 48 (47-50) mm Hg, p = 0.002; bicarbonate concentration 34 (32-35) vs 29 (28-30) mmol/L, p < 0.0001; and minute volume 9.7 (8.9-10.4) vs 10.6 (9.2-12.0) L/min, p = 0.26. There were no severe adverse effects with ACTZ administration.

CONCLUSIONS: Among patients with MA and COPD or OHS, early treatment with ACTZ did not shorten significantly the duration of MV compared with placebo.

TRIAL REGISTRY: clinical.trials.gov; NCT01499485; URL:.www.clinicaltrials.gov.