The Pulmonary Haemodynamic Effects of Almitrine Infusion in Men with Chronic Hypercapnia

1. Almitrine, an agonist of peripheral chemoreceptors, has been shown to be effective in lowering Paco₂ in patients with chronic obstructive lung disease. The aim of this investigation was to evaluate the pulmonary haemodynamic response to almitrine in clinically stable patients with chronic airflow obstruction and chronic hypercapnia (Paco₂ 7.1 ± 0.5 kPa, mean ± sd).

2. Seven men, aged from 55 to 64 years, had the following values for pulmonary function (means ± sd): FEV_1.0 0.67 ± 0.16 litre; VC 2.12 ± 0.52 litres; FEV_1.0/VC 33 ± 8%. They had haemodynamic monitoring during 1 h of almitrine (1 mg/kg intravenously) and solvent (placebo) in a random fashion while receiving 28% oxygen. Before infusion, six patients had evidence of pulmonary hypertension and the mean pulmonary artery pressure (PAP) for all seven patients was 4.3 ± 1.6 kPa (mean ± sd); the pulmonary vascular resistance (PVR) was 0.61 ± 0.22 kPa l⁻¹ s (mean ± sd).

3. There were no significant changes from baseline values during placebo. During almitrine, however, the PAP and right ventricular stroke work (mean ± sd) increased significantly at 30 min (6.0 ± 2.1 kPa, P < 0.001, 0.38 ± 0.12 J, P < 0.05, respectively) with maximum increase of PVR at 45 min (1.01 ± 0.34 kPa l⁻¹ s, P < 0.001, mean ± sd). The lowest Paco₂ (mean ± sd) was observed at the end of the infusion (5.7 ± 0.5 kPa, P < 0.001).

4. These results confirm the benefit of almitrine in lowering Paco₂ in patients with chronic airflow obstruction who have chronic hypercapnia but also demonstrate significant pulmonary vasoconstriction.