Venesection
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venesection phlebotomy indications procedure clinical
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Venesection (Therapeutic Phlebotomy)
Venesection (also called therapeutic phlebotomy or bloodletting) is the deliberate removal of a volume of blood — typically 450–500 mL per session — for therapeutic purposes. It is distinct from diagnostic phlebotomy (blood drawing for tests).
Indications
1. Hereditary Haemochromatosis (HH)
The primary and most important indication. HH is an autosomal-recessive disorder (>80% due to the HFE C282Y homozygous mutation) causing excessive intestinal iron absorption due to inappropriately low hepcidin expression. Iron accumulates in the liver, pancreas, heart, pituitary, skin, and joints, causing:
- Cirrhosis → hepatocellular carcinoma (200× increased risk)
- Diabetes mellitus (pancreatic islet destruction)
- Bronze skin pigmentation
- Cardiomyopathy/arrhythmias
- Hypogonadism, arthritis
Treatment: Regular phlebotomy steadily depletes tissue iron stores. With treatment, life expectancy is normal — Robbins, Cotran & Kumar, p. 813.
Protocol:
- Induction phase: 500 mL every 1–2 weeks until serum ferritin reaches low-normal range
- Maintenance phase: Every 2–3 months to keep ferritin ~50–100 µg/L
- Monitor: serum ferritin (primary target); TSAT monitoring during maintenance is not recommended as it fluctuates widely — Tietz Textbook of Laboratory Medicine, p. 1381
- Prerequisites: Hb >120 g/L, serum ferritin >25 µg/L, stable BP and pulse, adequate venous access, recent oral intake
2. Polycythaemia Vera (PV)
PV is a JAK2-mutant myeloproliferative neoplasm causing excess red cell production. Elevated haematocrit increases blood viscosity and thrombotic risk.
- Target: Haematocrit <45% (reduces thrombotic and cardiovascular events)
- Phlebotomy is first-line in low-risk PV; cytoreduction with hydroxyurea or ropeginterferon-alfa-2b is added in high-risk patients
- Ropeginterferon-alfa-2b achieves haematocrit <45% in ~85% vs ~60% with phlebotomy alone — Goldman-Cecil Medicine, p. 1756
- Ruxolitinib (JAK1/2 inhibitor) is used when phlebotomy-dependent PV is inadequately controlled on hydroxyurea
- Note: Iron supplementation is contraindicated in PV patients undergoing phlebotomy (iron deficiency suppresses erythropoiesis and helps maintain control)
3. Porphyria Cutanea Tarda (PCT)
PCT causes a blistering photosensitivity dermatosis due to impaired uroporphyrinogen decarboxylase activity; iron overload is a major precipitant.
- 500 mL venesection every 2 weeks until serum ferritin reaches low-normal range
- Typically requires 8–12 sessions to achieve remission
- Alternative/adjunct: oral chloroquine 125 mg twice weekly (releases porphyrins renally)
- Patients with anaemia (e.g., renal failure) may need concurrent erythropoietic agents — Goldman-Cecil Medicine, p. 1569
4. Chronic Mountain Sickness (Monge Disease)
At high altitude, chronic hypoxia drives extreme erythrocytosis. Venesection ± isovolumetric haemodilution is used widely when relocation to lower altitude is not possible — Miller's Anaesthesia, p. 3019.
5. Other (historical/emerging)
- Secondary haemochromatosis (thalassaemia, myelodysplastic syndrome) — phlebotomy generally avoided if anaemia present; iron chelation preferred
- Non-HFE haemochromatosis — same phlebotomy approach as HFE-HH
Procedure
| Step | Detail |
|---|---|
| Volume | 450–500 mL per session |
| Access | Antecubital fossa, 16–18G needle; alternate arms between sessions |
| Equipment | Standard blood donor bag with tubing, tourniquet, BP monitor, scales |
| Duration | ~15–30 minutes |
| Fluids | Adequate oral hydration pre-procedure; patient should not be fasting |
Contraindications / Prerequisites
- Hb <120 g/L (anaemia)
- Systolic BP <110 or >160 mmHg; diastolic <60 or >95 mmHg
- Pulse <50 or >100 bpm
- Serum ferritin <25 µg/L (in HH maintenance)
- Poor venous access
- Fasting state
Complications
| Complication | Notes |
|---|---|
| Vasovagal syncope | Most common; lie patient flat, raise legs |
| Haematoma | At venepuncture site |
| Hypovolaemia | Especially in elderly or cardiovascular disease |
| Phlebitis / venous scarring | With repeated sessions |
| Iron-deficiency anaemia | If phlebotomy is excessive |
Monitoring Parameters
| Condition | Primary Monitor | Target |
|---|---|---|
| HH (induction) | Serum ferritin | Low-normal range |
| HH (maintenance) | Serum ferritin | 50–100 µg/L |
| PV | Haematocrit | <45% |
| PCT | Serum ferritin | Low-normal range |
Mechanism of Benefit
Each 500 mL unit of blood contains approximately 200–250 mg of iron (haemoglobin carries ~0.5 mg Fe/mL of red cells). Repeated venesection depletes total body iron stores without drug-related toxicity. The body compensates with increased erythropoiesis, which in turn scavenges iron from storage depots — Medical Physiology, p. 1241.
Sources: Robbins, Cotran & Kumar – Pathologic Basis of Disease | Goldman-Cecil Medicine | Medical Physiology | Tietz Textbook of Laboratory Medicine | Miller's Anaesthesia | Emery's Elements of Medical Genetics
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