Cutoff Hemoglobin and Hematocrit Levels for Therapeutic Phlebotomy
For patients with polycythemia vera (PV), therapeutic phlebotomy should be performed to maintain hematocrit strictly below 45% for all patients, with a lower target of approximately 42% for women and African Americans due to physiological differences in baseline hematocrit values. 1, 2
Condition-Specific Cutoffs
Polycythemia Vera
- Maintain hematocrit <45% in all PV patients regardless of risk category 1
- Consider lower target (42%) for women and African Americans 1, 2
- This target is based on the CYTO-PV study showing reduced thrombotic complications with hematocrit <45% 1, 2
- Low-risk PV: phlebotomy + low-dose aspirin (81-100 mg/day) 1
- High-risk PV: phlebotomy + low-dose aspirin + cytoreductive therapy 1
Congenital Heart Disease with Cyanosis
- Therapeutic phlebotomy indicated when hemoglobin >20 g/dL AND hematocrit >65% 1
- Only perform phlebotomy when symptoms of hyperviscosity are present (headache, fatigue) 1
- Avoid routine repeated phlebotomies due to risk of iron depletion and stroke 1
Secondary Polycythemia
- Consider phlebotomy when hematocrit exceeds 52-55% 2
- Higher threshold than for PV due to different pathophysiology 2
Hemochromatosis
- Perform phlebotomy weekly or biweekly during initial iron depletion phase 3
- Monitor hemoglobin/hematocrit before each phlebotomy to ensure it doesn't fall below 80% of starting value 3
- Adjust frequency once serum ferritin reaches 50-100 μg/L 3
Practical Considerations
Phlebotomy Technique
- Remove one unit of blood (approximately 500 mL) per session 3
- Provide appropriate fluid replacement to avoid hypotension or fluid overload 1, 2
- Each unit of blood contains approximately 200-250 mg of iron 3
Monitoring
- Check hemoglobin/hematocrit before each phlebotomy session 3
- For PV patients, monitor for signs/symptoms of disease progression every 3-6 months 1
- For hemochromatosis, monitor serum ferritin every 10-12 phlebotomies during initial phase 3
Complications to Watch For
- Iron deficiency from excessive phlebotomy can lead to microcytosis and increased stroke risk 1
- Diagnostic phlebotomy itself can contribute to anemia (every 100 mL of blood drawn decreases hemoglobin by approximately 7.0 g/L) 4
- Patients with cardiovascular disease require careful monitoring during phlebotomy 1, 5
Special Populations
Elderly Patients
- Same hematocrit targets apply, but use more caution with fluid replacement 1
- Consider cytoreductive therapy if phlebotomy is poorly tolerated 1
High Altitude Residents
- Normal hematocrit ranges are higher at altitude (45-61% for men, 41-56% for women at 4000m) 6
- Adjust therapeutic targets accordingly for patients living at high altitude 6