Polycythaemia is a haematological disorder characterised by an abnormal increase in the volume of circulating red blood cells. This condition results in an elevated packed cell volume, increased haemoglobin concentration, and high total red cell mass. When blood becomes excessively thick, its viscosity rises significantly. High viscosity impairs smooth blood flow through the microvasculature, leading to sluggish circulation and reduced tissue oxygenation despite the abundance of red blood cells. Nurses must recognise that polycythaemia can be transient due to dehydration, or chronic due to intrinsic bone marrow disorders or chronic hypoxia.
Polycythaemia is broadly divided into two major categories based on its origin:
Understanding the root causes of polycythaemia helps guide clinical assessment and patient history taking. Primary cases are largely linked to acquired genetic mutations, such as the JAK2 gene mutation found in most individuals with polycythaemia vera. Secondary cases stem from conditions that create prolonged systemic hypoxia.
Common causes and risk factors include:
The clinical presentation of polycythaemia stems directly from hyperviscosity and expanded blood volume. Patients often appear ruddy or flushed in the face, a sign known as plethora.
Confirming polycythaemia requires a systematic laboratory workup to measure red cell parameters and identify the underlying cause. Initial tests include a full blood count, which consistently reveals elevated haemoglobin and haematocrit levels. Serum erythropoietin levels help differentiate primary from secondary forms; patients with polycythaemia vera typically have very low erythropoietin levels, whereas secondary cases show normal or elevated levels. Bone marrow aspiration and biopsy are performed if primary causes are suspected, looking for panmyelosis. Genetic testing for the JAK2 mutation is standard practice to confirm primary disease.
Management aims to reduce blood viscosity, prevent thrombotic events, and control symptoms. Therapeutic phlebotomy is the cornerstone of treatment, involving the regular removal of blood to maintain the haematocrit below target levels. Myelosuppressive agents, such as hydroxyurea, may be prescribed for high-risk patients to suppress bone marrow activity. Low-dose aspirin is frequently used to reduce the risk of microvascular thrombosis and painful complications. Nursing care involves monitoring fluid balance, assessing for signs of deep vein thrombosis or stroke, and educating patients on adequate hydration and avoiding tight clothing that impedes circulation.
Unmanaged or poorly controlled polycythaemia carries a high risk of life-threatening vascular events. The most frequent complications arise from thrombosis, including stroke, myocardial infarction, deep vein thrombosis, and pulmonary embolism. Paradoxically, bleeding episodes can also occur due to acquired von Willebrand syndrome or abnormal platelet function caused by extremely high cell counts. Over time, some patients with polycythaemia vera may progress to myelofibrosis or transform into acute myeloid leukaemia. With timely phlebotomy and medical therapy, many patients maintain a near-normal life expectancy.