RESUMO
Erythropoietin (EPO) controls red cell production. Hypoxaemia, reduced blood oxygen-carrying capacity and increased affinity of haemoglobin (Hb) for oxygen are the primary stimuli for EPO secretion. The effect of hyperoxaemia (arterial oxygen tension (Pa,O2) > 13.3 kPa) on EPO secretion has not been thoroughly studied and is not fully understood. The primary purpose of this study was to evaluate EPO production in patients with acute respiratory failure as well as to determine the effect of hyperoxaemia on EPO secretion in patients with and without anaemia. A prospective clinical study was carried out in a 14-bed general (medical and surgical) intensive care unit in a university hospital. Twenty-one patients with acute or acute on chronic respiratory failure, requiring mechanical ventilation, were included in this study. The patients were divided into two groups; group I comprised patients who developed anaemia, and group II patients who did not. EPO levels and haematological parameters were measured in venous blood under three oxygenation conditions: hypoxaemia, hyperoxaemia and normoxaemia. All patients exhibited high EPO levels during hypoxaemia (mean value 108.7 +/- 27 mU.mL-1 (+/- SD)). During hyperoxaemia, EPO levels decreased in both groups (mean value 21.6 +/- 15.2 mU.mL-1 in group I, 36.8 +/- 19 mU.mL-1 in group II). During normoxaemia, EPO levels increased again in group I patients, but in group II patients EPO production remained stable. In conclusion, hyperoxaemia inhibits erythropoietin secretion in spite of anaemia and low arterial oxygen tension. Hyperoxaemia may be a contributing factor to anaemia in intensive care unit patients under oxygen therapy.
