Management of Erythrocytosis (High Hematocrit)
The management of erythrocytosis should focus on identifying the underlying cause first, followed by targeted treatment with therapeutic phlebotomy reserved only for specific indications such as hematocrit >45% in polycythemia vera or >65% with symptoms in secondary erythrocytosis.
Diagnostic Approach
Initial Evaluation
- Complete blood count with peripheral smear
- Comprehensive metabolic panel
- Arterial blood gas analysis
- Serum erythropoietin level
- JAK2 mutation testing (V617F and exon 12)
- Iron studies (ferritin, transferrin saturation)
Classification of Erythrocytosis
Primary (Clonal) Erythrocytosis
- Polycythemia Vera (PV)
- Almost always associated with JAK2 mutation
- Low serum erythropoietin levels
- Polycythemia Vera (PV)
Secondary (Non-clonal) Erythrocytosis
- Normal or elevated serum erythropoietin
- Common causes:
- Hypoxic conditions (COPD, sleep apnea, high altitude)
- Renal disorders (cysts, tumors, renal artery stenosis)
- Post-renal transplant erythrocytosis
- Testosterone/androgen therapy
- Erythropoietin-secreting tumors
- Congenital causes (high-oxygen-affinity hemoglobinopathies)
- Medication-induced (SGLT2 inhibitors)
Treatment Approach
Polycythemia Vera
- Therapeutic phlebotomy to maintain hematocrit <45% 1
- Low-dose aspirin (81-100 mg daily) for all patients without contraindications
- Cytoreductive therapy for high-risk patients (age >60 years or history of thrombosis)
Secondary Erythrocytosis
Treat underlying cause:
- CPAP for sleep apnea
- Smoking cessation
- Management of renal disease
- Discontinuation of causative medications when possible
Selective phlebotomy only for:
Avoid routine phlebotomy in:
Important Considerations
Hydration Status
- Ensure adequate hydration before considering phlebotomy 1, 2
- Dehydration can falsely elevate hematocrit and exacerbate hyperviscosity symptoms
Iron Status
- Monitor iron status before repeated phlebotomies 1, 2
- Iron deficiency in erythrocytosis:
- Reduces oxygen-carrying capacity
- May cause symptoms mimicking hyperviscosity
- Can increase risk of stroke and myocardial ischemia 1
Phlebotomy Technique
- Remove 300-450 mL of blood weekly or twice weekly until target hematocrit is reached 1
- Always replace with equal volume of fluid (saline or dextrose) 1
- Schedule follow-up hematocrit check in 1-2 weeks after phlebotomy 2
Special Populations
Cyanotic Congenital Heart Disease
- Phlebotomy only for hematocrit >65% with symptoms of hyperviscosity 1
- Avoid aggressive phlebotomy due to risk of stroke 1
- Target hematocrit 55-60% in chronic obstructive pulmonary disease 1
Post-Renal Transplant Erythrocytosis
- Associated with increased thrombosis risk
- Angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers are effective in lowering hematocrit 1
Monitoring and Follow-up
- Complete blood count every 2-4 weeks initially, then every 3 months once stable 2
- Annual cardiovascular risk assessment
- Regular evaluation for symptoms of hyperviscosity
- Monitor iron status periodically in patients undergoing regular phlebotomy
Common Pitfalls to Avoid
- Performing routine phlebotomy in asymptomatic patients with secondary erythrocytosis
- Failing to check iron status before repeated phlebotomies
- Not addressing dehydration before phlebotomy
- Overlooking underlying causes of secondary erythrocytosis
- Excessive phlebotomy leading to iron deficiency and paradoxical worsening of symptoms
By following this structured approach to diagnosis and management, patients with erythrocytosis can be appropriately treated while minimizing complications related to both the condition and its treatment.