What is Venesection?

Venesection is a procedure which involves removing a pint (half a litre) of blood from a vein in the arm. This is similar to the procedure used when donating blood.
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Why is it necessary to have a Venesection?

When the number of red cells in the blood increases, the blood becomes thicker and more viscous, and the blood circulation in the body becomes sluggish. This can increase the risk of developing complications such as blood clots (thrombosis). Removing the excess blood cells through venesection is the simplest and quickest way to reduce this risk.
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Venesection is the recommended treatment for:

• Polycythaemia – A blood disorder where the blood becomes thicker due to the excessive production of red blood cells. As a result, the blood cannot flow smoothly, especially through the smaller blood vessels. This increases the risk of blood clots, heart attacks and strokes.
• Haemochromatosis – A condition caused by excessive levels of iron in the body built up over many years. This can be primary haemochromatosis (which is genetic and inherited in nature), or could be secondary in nature (due to patients who have had many blood transfusions such as recovering post-transplant patients). The excess iron can result in:
  • a surplus production of red blood cells which causes the blood to thicken and increases the risk of blood clots.
    
  • iron deposits in the organs, causing damage to the healthy tissue, which increases the risk of insulin-dependent diabetes, liver damage, arthritis, infertility, and impotence in men.
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What are the risks and side effects of a Venesection?

A venesection is a very safe and straightforward procedure, but some patients may experience side-effects including:

• Discomfort or pain at the site of needle insertion
• Slight bleeding after the needle is removed
  
• Bruising at the site of needle insertion
  
• Dizziness. Some patients may develop low blood pressure and experience dizziness during and for a short period after the procedure due to the reduced blood volume and the resulting drop in blood pressure. This should wear off with rest. Patients should get up slowly to avoid feeling dizzy.
• Tiredness – Some patients may feel tired or “washed out” for a few days after the procedure. This effect should also wear off with rest.
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How is a Venesection performed?

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A tourniquet will be applied to your arm in the same way as when you have your blood taken. Next, a cannula will be inserted into one of the large veins in your arm. The cannula is connected to a collection bag via a tube to collect the blood. Once the desired amount of blood is withdrawn, some patients are given an infusion of fluid to replace the volume of blood given.
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The cannula can then be removed and slight pressure will be applied to the insertion site for a few minutes. After that, a small dressing will be applied. You will be asked to rest for another 15-30 minutes, and your blood pressure will be monitored.
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How long is the Venesection?

The venesection procedure should take less than an hour to complete. Most patients are able to carry on with their day’s activities immediately after the procedure. However, you are advised to avoid lifting heavy loads or performing strenuous activities for the next 24 hours.
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How often is the Venesection treatment?

The number of sessions and its frequency varies depending on your specific condition and your red blood counts. Most patients start with one session every few weeks. Once the condition is under control, each session may only be required every 6 to 12 weeks.

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Disclaimer:
The information on the Centre For Clinical Haematology website is intended for educational use.  It should not be considered or used as a substitute for medical advice, diagnosis or treatment from a qualified health professional.