External Ventricular Drain

What is an External Ventricular drain (EVD)?

An External ventricular drain (EVD) is a temporary method of draining cerebrospinal fluid (CSF) from the ventricles in the brain. CSF is a clear liquid that protects and transports nutrients around the brain. The large spaces in the brain that hold cerebrospinal fluid (CSF) are called ventricles. If CSF flow is blocked, it builds up and causes pressure. This is called hydrocephalus.

Hydrocephalus can lead to a build-up of pressure in the brain causing neurological deterioration. In this case, surgery may be needed to put a thin plastic tube in the brain’s ventricle. This tube connects to an External Ventricular Drain (EVD), which lets extra CSF drain out.

The drainage system works with gravity. This means the amount of CSF that can drain away depends on the position of the drip chamber or cylinder beneath the level of ventricles.

Why is it needed?

There are many reasons for using external ventricular drainage (EVD). These include;

• Reducing the pressure inside the brain caused by a build-up of CSF. This can result from a temporary blockage or abnormal flow of CSF within the brain.
• Diverting infected CSF from the brain and giving antibiotics directly into the CSF to treat the infection.
• Draining excess fluid and/or blood if a person has had brain surgery or has experienced a bleed in their brain such as a Subarachnoid haemorrhage.

Preparation for an EVD

In many cases an EVD is done in emergency conditions. You or your Next of kin maybe updated prior to the procedure. Before the operation, the surgeon may visit you to explain the operation in more detail, discuss any worries you may have and ask you to sign a consent form giving permission. Relatives of adults cannot consent for the procedure. If there any medical problems, like allergies, please tell the doctors about these.

To prepare for the operation a small area of hair will need to be shaved away.

How is the drain inserted?

The drain will be inserted in an operation under general anaesthetic in the operating theatre.

A surgical incision of approximately 3cm is made along the scalp and a small hole fashioned into the skull. One end of the drain is placed directly into the ventricles of the brain. This tube is then tunnelled below the skin and brought out onto the scalp. It will be coiled and stapled or sutured to the skin to secure it in its place and then connected to a drainage bag system.

You will have a dressing where the catheter was inserted, and another dressing on the exit site.

What are the risks?

Risks of EVD insertion and of general anaesthetic will be discussed with yourself or relative prior to the insertion of the EVD.

Risks of having an EVD in place include;

• Infection
• Blocked Drain
• Excessive Drainage
• CSF leakage
• Accidental removal of EVD

What happens afterwards?

You will return to the ward to recover after the procedure.

The nursing team will carry out regular neurological observations. They will also need to take regular measurements of the amount of CSF draining away and record this. The fluid in the drain maybe clear or even blood stained: The nursing or medical team will observe this.

There is a risk of infection with an EVD, but this will be minimised by using gloves and sterile equipment whenever a nurse or doctor must open the system.

If the doctors suspect an infection, they may take samples of CSF from the drain to send for testing in the laboratories. Samples are taken through the port on the tubing.

The tubing can become accidently disconnected, which would allow the CSF to drain away at too fast a rate. If the tubing becomes disconnected, please call a nurse immediately.

What can you do to help?

• To avoid any infection please do not touch the EVD drainage system or site on your head.
• If you need to change position either to sit or stand up or lay down, then please inform one of the nursing team – this is so the drain can be clamped to avoid excessive drainage.
• If you notice any clear fluid leaking from the EVD site, Or see a stain on the pillow, please inform one of the nursing or medical team immediately.
• If any part of the tube becomes disconnected, please inform one of the nursing or medical team members immediately.
• If too much CSF drains, it can cause low pressure in the brain. You might feel pale, sweaty, sick, or very sleepy. If this happens, please tell a nurse or doctor right away.

How long will the EVD last?

This varies from person to person, depending on the reason why the EVD was needed in the first place. However, it is a temporary method of draining CSF and is rarely used for more than 14 days. You will need to stay in hospital until the drainage system is removed.

If you need a ventricular drainage for a longer period another method may be suggested. The doctors will explain this in more detail if it is likely.

When is the EVD removed?

The Neurosurgical team will review the need for the EVD daily. The EVD will be challenged by raising the EVD chamber against gravity. This is to see if the CSF will be absorbed naturally by your own body.

If this is the case, then the EVD can be clamped and eventually removed.

If the CSF is not naturally absorbed, the EVD may need to remain, it can be challenged again later, or a permanent alternative method of CSF diversion may be required. This will be discussed with you at the time.

How is the EVD removed?

In most situations, it is removed on the ward without the need of general anaesthetic.

Local anaesthetic can be given, and the drain removed- the site can then be sutured with a stitch.

Are there any long-term effects of having EVD?

There are no long-term effects of having EVD, other than a small scar where the catheter was inserted and another small scar at the exit site. These will fade in time. Depending on the reason for the EVD, you may need a permanent system called a shunt.

Driving advice

The DVLA advise no driving six months after an EVD insertion due to the risk of developing seizures. This can lead to a ban. Please contact the DVLA for more advice.