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External ventricular drain (EVD)

What is an external ventricular drain (EVD)?

Cerebrospinal fluid is a protective fluid that surrounds the brain and spinal cord. It flows through the fluid filled spaces in the brain called ventricles.

Our body normally controls the amount of cerebrospinal fluid in these spaces by production and re-absorption, but sometimes we need to drain away some of this fluid. We do this temporarily by using an external ventricular drain (EVD).

An EVD is a surgery that involves a thin catheter (tube) that goes into the ventricles of the spine.

The outside end of the catheter is then attached to a drainage system that is made up of a drip chamber and drainage bag. This is then placed on a stand by your child’s bed and we can control how much cerebrospinal fluid drips out.

Illustration of external ventricular drain going from the brain to outside of the body

Why does my child need an EVD?

There are few reasons for needing an EVD including:

  • Inside the skull there are is brain tissue, blood and cerebrospinal fluid. If any of these in our skull increase in volume we can become unwell because of the pressure this causes. To keep control of this, we use intracranial pressure (ICP) monitoring.
  • Raised intracranial pressure can also be caused by a build up of cerebrospinal fluid in the ventricles. This can be due to abnormal flow and abnormal absorption, a blockage, an injury or surgery. An EVD is used to drain off excess cerebrospinal fluid and maintain a healthy pressure inside the brain.
  • To manage and treat infection. An EVD can be used to divert infected cerebrospinal fluid away from the brain into the drainage system. Antibiotics can also be given through the drainage system directly into the ventricles to treat the cerebrospinal fluid infection.

How is the EVD inserted?

The EVD is put in by a surgeon in surgery. Your child will have a general anaesthetic so they will be asleep and not feel anything.

They will be given pain relief to your child to reduce their pain and discomfort. During the operation, a tiny hole is made so a thin catheter (tube) tip can be put into the ventricles to let the cerebrospinal fluid drain out.

This is then stitched into place and covered with a head bandage. A head bandage or dressing is needed to try to stop them from catching or pulling the drain. This also acts as a barrier to infection.

Your child will be taken to the recovery room post-anaesthetic care unit (PACU) and will then returned to the ward when your child is ready.

The surgeon and anaesthetist will come and speak to you before the procedure to answer any question that you have.

What are the risks of having an EVD?

Every anaesthetic and procedure carries a risk of complications. These will be explained to you in more depth by the neurosurgeon and anaesthetist before your child has the EVD.

It is important to remember that your child is unwell and the neurosurgeon has suggested an EVD as treatment. If left untreated, their condition is likely to get worse and have a greater risk to their health.

It can be difficult for younger children to understand the importance of the drain and how changing their position affects the drainage of cerebrospinal fluid. As a result children with an EVD in place need close supervision.

What do I need to consider when caring for my child while the EVD is in place?

The nurses on the ward are trained to look after children with EVD’s. They will keep a close eye on them and do hourly checks (even overnight) to monitor the amount and type of drainage.

The nurses will need to measure the position of the drainage chamber against your child’s head. They will do this by using a light. This will not cause any harm or pain to your child. The level of the drain in relation to the head is how the flow is regulated.


If the drain is lower than where it should be then more fluid will drain and if it is higher then less fluid will drain. It is important that you let the staff know if your child’s position changes so the flow can be regulated properly by moving the drain to match their position. If they move without us knowing, please inform us straight away so we can adjust the drain and monitor them.

You may also see the doctors taking samples of cerebrospinal fluid or giving your child antibiotics through the EVD. These are routine procedures and should not cause any pain to your child.

The nurses will encourage you to care for your child as much as you feel you can. They also understand that this can be a worrying time and that it can be daunting caring for your child when they have an EVD. The nurses are here to support you through out this experience and to help you to care for your child. Please ask as many questions as you like and talk about your worries.

How long will my child need an EVD for?

This will depend on the reason why your child needs an EVD. The length of time will depend on your child’s condition, so it may be a few days or a few weeks. Your doctor may be able to give you a better idea of how long it will need to stay in for.

Your child will need to stay on the ward when the EVD is in place. It is important to remember that an EVD is only a temporary solution and if your child needs a long term solution, the doctor will discuss this with you.

How is an EVD removed?

The EVD will be clamped on the ward before it is removed by the neurosurgical team.

Pain relief can be given to your child as a precaution before this. If possible the drain will be removed in the treatment room with a play specialist to support and distract your child.

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Please note: this is a generic information sheet relating to care at Sheffield Children’s NHS FT. These details may not reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If this information has been translated into another language from English, efforts have been made to maintain accuracy, but there may still be some translation errors. If you are unsure about any of the guidance in this resource or have specific questions about how it relates to your child, always ask your healthcare professional for further advice.

Resource number: NSC2

Resource Type: Article

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