Introduction In adult defined by a Hct > 55% Most common cause is chronic hypoxemia secondary to lung disease Causes of Secondary Polycythemia Hypoxemia COPD Restrictive lung disease Cyanotic congenital heart High altitude Ectopic erythopoeitin Renal adenocarcinoma Renal cysts Hepatocellular carcinoma Cerebellar hemangio-blastoma Uterine leiomyomas Smokers polycythemia Carbon monoxide causes tissue hypoxemia and release of EPO; for unknown reasons there is a decrease in plasma volume Stress polycythemia Looks like dehydration and found in obese, hypertensive males Dehydration Relative (secondary to reduction in plasma volume but same number of RBCs) Evaluation Causes SaO2 EPO RBC mass Plasma Volume Hypoxemia ↓ ↑ ↑ normal Polycythemia rubra vera normal ↓ ↑ ↑ Ectopic erythopoeitin normal ↑ ↑ normal Smokers polycythemia variable ↑ ↑ ↓ Stress polycythemia normal normal normal ↓ Dehydration normal normal normal ↓ Treatment Serial phlebotomy Myelosuppressive agents hydroxyurea Daily aspirin to prevent thrombotic complications