Increased erythropoietin synthesis in patients with COLD or left heart failure is related to alterations in renal haemodynamics.
The mechanisms controlling erythropoietin (EPO) synthesis by the kidney in patients with chronic obstructive lung disease (COLD) or congestive left heart failure (CLHF) remain incompletely understood. Renal dysfunction occurs as a consequence of decreased renal blood flow (RBF) in these diseases. Because alterations in renal haemodynamics may affect EPO synthesis and red blood cell production, we investigated the potential relationships between renal function and plasma EPO synthesis in patients with COLD or CLHF. Thirty-two patients with COLD and 13 with CLHF underwent determination of renal physiology parameters, plasma EPO levels and haemoglobin levels. Plasma EPO concentrations were increased in patients with COLD or CLHF as compared to normal subjects, and were inversely correlated to haemoglobin concentrations. In patients with COLD or CLHF, plasma EPO was negatively correlated with both RBF and renal oxygen delivery (ROD) and positively correlated with filtration fraction. Plasma EPO was not correlated with glomerular filtration rate, fractional excretion of sodium, PO2 or PCO2. Among the patients with COLD, those with polycythemia (haemoglobin > 150 g L-1) had lower plasma EPO and higher RBF and ROD values than those with normocythemia (haemoglobin < or = 150 g L-1). Taken together, our data suggest that in patients with COLD or CLHF the critical determinant for EPO production is impairment of renal haemodynamics.