External Ventricular Drainage Explained

What is an External ventricular Drain (EVD)

It is a piece of soft, flexible tubing inserted into the ventricles of the brain, to drain off Cerebrospinal fluid (CSF). This fluid is then collected into an external drainage system This allows the fluid to be measured and monitored by nursing and medical staff.

What is a ventricle and what is Cerebrospinal fluid?

Ventricles act as reservoir and drainage system for a liquid called Cerebrospinal fluid (CSF) which surrounds the brain and spinal cord. It acts to protect, nourish and discard waste products from these vital organs.

  

Why do we need to insert an External Ventricular Drain?

Sometimes the ventricular system doesn't work as well as it should especially when a brain has swollen after brain injury, infection, tumour or after a brain haemorrhage.

The CSF is unable to flow freely and can build up, causing the ventricles to swell and create pressure within the brain. This is called Hydrocephalus.

This needs to be treated urgently as it is a serious and potentially life-threatening condition.

Insertion of the External Ventricular drain is a temporary method of treatment to help drain CSF fluid.

Occasionally in some people, further intervention may be required and the options for this will be discussed with you if this becomes necessary.

What does the external ventricular drain do?

It acts as a substitute for the ventricular system by draining the CSF into the external system. The nurses observe the CSF for amount and colour of the CSF and to observe the amount drained each hour, and to observe for any evidence of blockage.

If there is a problem the nurses will then report this to the medical staff and appropriate action taken.

Small samples of CSF can also be taken from it to check for infection and antibiotics can also be administered through it if required.

How is it put in?

The EVD is inserted in theatre under general anaesthetic (while the patient is asleep). It is a quick, simple procedure done under sterile conditions in theatre.

After the EVD has been inserted

The patient will be observed closely and the drain set at a level specified by the neurosurgeon.

The fluid flows through the tubing into the measuring chamber (burette) and the amounts monitored closely by staff.

The amount of drainage is monitored and recorded hourly.

If too little or too much fluid drains, then the height of the drain may need to be adjusted.

The nurses will also perform neurological observations at regular intervals to detect development of any problems and will inform medical staff immediately if this is the case.

Are there any risks with having an External ventricular Drain?

• There is a risk of infection , so close observation of the fluid is very important. This can be treated with antibiotics.

• Draining too much fluid (overdrainage) can cause problems such as headache or bleeding and bruising to the surface of the brain.

• The drain can become blocked or pulled out requiring replacement

• The drain can leak from the entry point through the skin. This may require extra stitches to close the skin around the tubing or replacement of the drain.

 The neurosurgeon will discuss these risks in detail with you before the procedure.

How is it removed?

The EVD is removed on the ward and a suture (stitch) will need to be put in to prevent any leakage of CSF after removal. This suture can be removed after 7 days.