Treatment for High Hematocrit

Initial Assessment and Risk Stratification

The National Comprehensive Cancer Network recommends determining if high hematocrit is due to polycythemia vera (PV) or secondary causes, and for PV, risk stratification should be performed based on age and history of thrombosis 4
Low-risk PV patients are defined as those with age <60 years and no history of thrombosis, while high-risk patients are those with age ≥60 years or history of thrombosis 1, 2, 4

The National Comprehensive Cancer Network recommends phlebotomy to maintain hematocrit <45% for all PV patients, regardless of risk, with an induction phase of 300-450 ml blood withdrawn weekly or twice weekly until target hematocrit is reached, and a maintenance phase with same blood volume per phlebotomy and intervals determined by hematocrit levels 2, 3, 5
Low-dose aspirin (81-100 mg/day) is recommended unless contraindicated, and aggressive management of cardiovascular risk factors is also recommended 1, 2, 3
Cytoreductive therapy is recommended for high-risk PV patients, with first-line options including hydroxyurea, interferon alfa-2b, peginterferon alfa-2a, or peginterferon alfa-2b 1, 2, 4

Treatment of the underlying cause is recommended, such as COPD, sleep apnea, or smoking, and judicious phlebotomy to hematocrit of 55-60% may be considered for patients with cyanotic congenital heart disease or high oxygen-affinity hemoglobinopathy 7

The target hematocrit may need individualization, such as 42% for women and/or patients with progressive or residual vascular symptoms, and overly aggressive phlebotomy should be avoided in patients with hypoxic conditions due to risk of stroke 2, 7
Phlebotomy is indicated for patients with pulmonary arterial hypertension and right-to-left shunts if hematocrit is above 65% and patient is symptomatic, and iron supplementation should be avoided unless there is documented severe tissue iron deficiency with detrimental symptoms 3, 8

Regular monitoring of hematocrit levels is recommended, as well as monitoring for thrombotic events, which are the main cause of morbidity and mortality, and watching for disease progression to myelofibrosis or acute myeloid leukemia 2, 3, 4, 5, 6

Complete response is defined as hematocrit <45% without phlebotomy, platelet count ≤400 × 10^9/L, WBC count ≤10 × 10^9/L, and no disease-related symptoms, while partial response is defined as hematocrit <45% without phlebotomy or response in three or more other criteria 1, 2

Iron supplementation should be avoided in PV patients unless specifically indicated, as it may worsen erythrocytosis, and phlebotomy alone may not be sufficient for high-risk PV patients, and the CYTO-PV study demonstrated that maintaining hematocrit <45% resulted in significantly lower rates of cardiovascular death and thrombotic events compared to a target of 45-50% 2, 3, 4, 5