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Emergency And Acute Medicine – Polycythemia
Polycythemia is defined as an increase in hemoglobin above the normal range, typically hemoglobin >17.5 g/dL or hematocrit >52% in men and hemoglobin >16 g/dL or hematocrit >48% in women. Symptoms are largely related to increased blood viscosity, which rises exponentially when the hematocrit exceeds 60%, predisposing patients to thrombotic and hyperviscosity complications.
Polycythemia may be relative, primary, or secondary. Relative (apparent) polycythemia results from decreased plasma volume rather than true red blood cell mass increase. Acute causes include dehydration, while chronic forms include Gaisbock syndrome, commonly seen in obese, hypertensive, middle-aged smokers. Primary erythrocytosis refers to polycythemia vera, a stem cell disorder characterized by panhyperplasia of bone marrow elements with increased red blood cells, leukocytes, and platelets. Most cases involve a JAK2 mutation, rendering hematopoietic cells hypersensitive to erythropoietin. It typically affects older adults, may progress to myelofibrosis or acute leukemia, and carries a high thrombotic risk. Secondary polycythemia results from increased erythropoietin production, often due to chronic hypoxia (such as chronic lung disease, sleep apnea, obesity hypoventilation syndrome, congenital heart disease, high altitude, or chronic carbon monoxide exposure) or renal and neoplastic causes that stimulate erythropoietin production. Drug-related causes include androgen use, recombinant erythropoietin abuse, and blood doping. Genetic disorders and certain infections may also contribute.
Clinical manifestations reflect hyperviscosity and thrombosis. Patients may report headache, dizziness, fatigue, dyspnea, visual disturbances, and paresthesias. Pruritus, especially after warm bathing, and erythromelalgia characterized by burning pain, redness, and warmth of the extremities are classic features of polycythemia vera. Thrombotic events are common and may involve arterial or venous systems, including stroke, myocardial infarction, deep vein thrombosis, pulmonary embolism, and unusual sites such as hepatic or cerebral veins. Hemorrhagic manifestations such as epistaxis and gingival bleeding may occur due to platelet dysfunction. Splenomegaly and hepatomegaly are common in polycythemia vera.
Evaluation begins with a complete blood count and assessment of volume status to distinguish relative from true erythrocytosis. Pulse oximetry, erythropoietin levels, carboxyhemoglobin levels, and appropriate imaging help identify secondary causes. A low erythropoietin level strongly suggests polycythemia vera. Detection of a JAK2 mutation by PCR is diagnostic in most cases. Elevated platelet count, leukocytosis, elevated vitamin B12, and splenomegaly further support the diagnosis.
In the emergency setting, management focuses on complications of hyperviscosity and thrombosis. Patients with hematocrit greater than 60% or symptoms of hyperviscosity require fluid resuscitation unless contraindicated by heart failure, followed by therapeutic phlebotomy with careful replacement using isotonic saline. The goal is gradual reduction of hematocrit to safer levels, generally around 45%. Aspirin may be administered in thrombocytosis without bleeding risk. Long-term management includes periodic phlebotomy to maintain target hematocrit, low-dose aspirin, and cytoreductive therapy such as hydroxyurea in high-risk patients.
Patients with new diagnosis, hematocrit above 60%, symptoms of hyperviscosity, or unstable comorbid conditions should be admitted. Asymptomatic patients with stable vital signs and controlled hematocrit may be discharged with close hematology follow-up. It is essential to distinguish polycythemia vera from secondary causes because of the significantly higher risk of thrombotic complications associated with the primary disorder.
Polycythemia is defined as an increase in hemoglobin above the normal range, typically hemoglobin >17.5 g/dL or hematocrit >52% in men and hemoglobin >16 g/dL or hematocrit >48% in women. Symptoms are largely related to increased blood viscosity, which rises exponentially when the hematocrit exceeds 60%, predisposing patients to thrombotic and hyperviscosity complications.
Polycythemia may be relative, primary, or secondary. Relative (apparent) polycythemia results from decreased plasma volume rather than true red blood cell mass increase. Acute causes include dehydration, while chronic forms include Gaisbock syndrome, commonly seen in obese, hypertensive, middle-aged smokers. Primary erythrocytosis refers to polycythemia vera, a stem cell disorder characterized by panhyperplasia of bone marrow elements with increased red blood cells, leukocytes, and platelets. Most cases involve a JAK2 mutation, rendering hematopoietic cells hypersensitive to erythropoietin. It typically affects older adults, may progress to myelofibrosis or acute leukemia, and carries a high thrombotic risk. Secondary polycythemia results from increased erythropoietin production, often due to chronic hypoxia (such as chronic lung disease, sleep apnea, obesity hypoventilation syndrome, congenital heart disease, high altitude, or chronic carbon monoxide exposure) or renal and neoplastic causes that stimulate erythropoietin production. Drug-related causes include androgen use, recombinant erythropoietin abuse, and blood doping. Genetic disorders and certain infections may also contribute.
Clinical manifestations reflect hyperviscosity and thrombosis. Patients may report headache, dizziness, fatigue, dyspnea, visual disturbances, and paresthesias. Pruritus, especially after warm bathing, and erythromelalgia characterized by burning pain, redness, and warmth of the extremities are classic features of polycythemia vera. Thrombotic events are common and may involve arterial or venous systems, including stroke, myocardial infarction, deep vein thrombosis, pulmonary embolism, and unusual sites such as hepatic or cerebral veins. Hemorrhagic manifestations such as epistaxis and gingival bleeding may occur due to platelet dysfunction. Splenomegaly and hepatomegaly are common in polycythemia vera.
Evaluation begins with a complete blood count and assessment of volume status to distinguish relative from true erythrocytosis. Pulse oximetry, erythropoietin levels, carboxyhemoglobin levels, and appropriate imaging help identify secondary causes. A low erythropoietin level strongly suggests polycythemia vera. Detection of a JAK2 mutation by PCR is diagnostic in most cases. Elevated platelet count, leukocytosis, elevated vitamin B12, and splenomegaly further support the diagnosis.
In the emergency setting, management focuses on complications of hyperviscosity and thrombosis. Patients with hematocrit greater than 60% or symptoms of hyperviscosity require fluid resuscitation unless contraindicated by heart failure, followed by therapeutic phlebotomy with careful replacement using isotonic saline. The goal is gradual reduction of hematocrit to safer levels, generally around 45%. Aspirin may be administered in thrombocytosis without bleeding risk. Long-term management includes periodic phlebotomy to maintain target hematocrit, low-dose aspirin, and cytoreductive therapy such as hydroxyurea in high-risk patients.
Patients with new diagnosis, hematocrit above 60%, symptoms of hyperviscosity, or unstable comorbid conditions should be admitted. Asymptomatic patients with stable vital signs and controlled hematocrit may be discharged with close hematology follow-up. It is essential to distinguish polycythemia vera from secondary causes because of the significantly higher risk of thrombotic complications associated with the primary disorder.
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