The effects of almitrine administration on pulmonary gas exchange and pulmonary and systemic hemodynamics were assessed in eight patients with severe acute respiratory failure (ARF) secondary to sepsis or shock. A control group of five patients not receiving the drug were submitted to the same protocol. All the patients were sedated, paralyzed, and mechanically ventilated. Measurements were made before (BASELINE), during (ALM 15), at the end of (ALM 30), and at 30 minute intervals after (POSTALM 30, 60, 90, 120) the intravenous (IV) infusion of 0.5 mg/kg body weight of almitrine in 30 minutes. Almitrine produced an increase in PaO2 from 86 +/- 14 (BASELINE) to 129 +/- 69 (ALM 15) and 129 +/- 86 mm Hg (ALM 30). The PaO2 quickly declined after stopping the infusion. The P(A-a)O2 and QVA/QT decreased with almitrine administration. The Ppa and QT increased transiently at ALM 30. We conclude that IV almitrine improves gas exchange and may be useful in the management of ARF.