Therapeutic Phlebotomy for Elevated Hematocrit
Therapeutic phlebotomy is indicated when the hematocrit exceeds 45% in patients with polycythemia vera, regardless of risk category. 1, 2
Hematocrit Thresholds for Therapeutic Phlebotomy
Polycythemia Vera (PV)
- Target hematocrit: <45% for all PV patients 1, 2
- This target is based on the CYTO-PV study which demonstrated reduced thrombotic events when hematocrit is maintained below 45% 2
- This applies to both low-risk (age <60 years, no prior thrombosis) and high-risk (age ≥60 years and/or prior thrombosis) patients 1, 2
- For female patients, a lower threshold (42%) may be appropriate in some cases 1
Severe Erythrocytosis (Non-PV)
- Immediate phlebotomy indicated when:
- Hemoglobin >20 g/dL or hematocrit >65% with symptoms of hyperviscosity 2
- These extreme levels require urgent intervention regardless of underlying cause
Phlebotomy Procedure
- Remove 1 unit of blood (approximately 450-500 mL)
- Replace with equal volume of dextrose or saline to maintain intravascular volume 2
- Monitor for symptom resolution
- Caution: Aggressive phlebotomy without adequate volume replacement can worsen symptoms 2
Risk Stratification in PV
| Risk Category | Definition | Treatment Approach |
|---|---|---|
| Low-risk | Age <60 years AND no prior thrombosis | Phlebotomy + low-dose aspirin |
| High-risk | Age ≥60 years OR prior thrombosis | Phlebotomy + low-dose aspirin + cytoreductive therapy |
Additional Indications for Cytoreductive Therapy
Even in low-risk patients, consider adding cytoreductive therapy when:
- Frequent or poorly tolerated phlebotomy requirement 1
- Symptomatic or progressive splenomegaly 1
- Platelet count >1,500 × 10^9/L 1
- Progressive leukocytosis 1
- Severe disease-related symptoms (pruritus, night sweats, fatigue) 1
Monitoring
- Evaluate hematocrit levels every 3-6 months or more frequently if clinically indicated 1
- Monitor for signs of disease progression to myelofibrosis or acute myeloid leukemia 1
- Assess for thrombotic or bleeding complications 2
- Manage cardiovascular risk factors aggressively 1, 2
Common Pitfalls to Avoid
- Inadequate volume replacement during phlebotomy - can worsen hyperviscosity symptoms 2
- Ignoring iron status - excessive phlebotomy can lead to iron deficiency, which may increase stroke risk 2
- Suboptimal hematocrit control - real-world data shows many patients have hematocrit >50% despite treatment 3
- Failure to recognize need for cytoreductive therapy - when phlebotomy alone is insufficient 1
- Inappropriate iron supplementation - should only be given for severe symptomatic iron deficiency 2
Special Considerations
- In patients with ADPKD and erythrocytosis, consider ACE inhibitors or ARBs before therapeutic phlebotomy 2
- Measurement considerations: hematocrit values can be falsely elevated in hyperglycemia and with prolonged sample storage 2
Maintaining hematocrit <45% is crucial for reducing thrombotic risk, which is the primary cause of morbidity and mortality in PV patients 4, 5.