RESUMO
Chronic polycythaemia in people living at high altitude is associated with hypoxaemia due to a marked reduction in hypoxic and hypercapnic drives. The effect of almitrine, a chemoreceptor stimulant, was evaluated in 40 patients, with haematocrit values over 57%, living in La Pa2 (3,600-4,000 m). Two studies were carried out. The aim of the first was to assess the ventilatory response, and the increase in PaO2 due to almitrine in a double blind, placebo controlled protocol including 40 patients (mean haematocrit 66.8%). Almitrine was given orally at a dose of 3 mg X kg-1. Variance analysis showed that three hours later there was a significant increase in PaO2 (+0.46 kPa), pH and respiratory frequency, with a significant reduction in PaCO2 (-0.4 kPa). The increase in ventilation (+17%) was not significant. The aim of the second study was to assess the effect of almitrine on the polycythaemia. It was given orally at a dose of 1.5 mg X kg-1 X day-1 to twelve patients over a four week period. Blood gases, ventilation (VE), oxygen consumption (VO2), carbon dioxide, production (VCO2) and haematocrit were measured every week. There was a slight but significant reduction in haematocrit (-3.5%). PaO2 and all the other measured parameters (VE, PaCO2, pH, VO2 VCO2) remained constant. The reduction in haematocrit was not therefore due to an increase in diurnal PaO2 but is perhaps due to the improvement in pulmonary ventilation during sleep.
