External Ventricular Drain (EVD)

What is an external ventricular drain (EVD)?

The External Ventricular Drain (EVD) is a meticulously performed procedure that involves surgically draining a surplus of cerebrospinal fluid (CSF) from the ventricles of the brain. Cerebrospinal fluid is considered a protective fluid that engulfs the spinal cord and brain.

An EVD procedure involves precisely placing a catheter, a fine plastic tube, in the brain’s ventricles. The catheter is attached to an external drainage system outside the body.

Why is an external ventricular drain utilised?

There are several reasons an external ventricular drain is considered, which consist of the following:

1. Alleviating the increased pressure in the brain due to the accumulation of cerebrospinal fluid.
2. Strategically diverting the flow of cerebrospinal fluid and directly administering antibiotics in the fluid to resolve the infection.
3. Removal of the build-up of fluid or blood in the brain, which is common after surgery or from bleeding in the brain.

How do you safely insert an external ventricular drain?

The procedure is carried out while the patient remains heavily sedated under general anaesthetic. The drainage tube is carefully fed beneath the skin through the exit route. The potential exit route is thoroughly discussed ahead of the procedure so you are comfortable with this decision.

During the EVD procedure, the medical team closely supervises the entire process, explaining beforehand how the system works. Consistent measurements of the exact output of cerebrospinal fluid are accurately recorded and captured. It’s important to monitor the consistency of the amount of CSF draining from the system to ensure the outflow does not happen too quickly.

What happens after the procedure?

After the EVD procedure, you will be transferred to the recovery unit, where you will be given sufficient time for the anaesthetic to wear off. A light dressing is carefully applied to the area where the catheter was placed and the exit route. You will be closely monitored during this time for any signs of discomfort or complications. Once you are fully awake and stable, you will be transferred to a regular hospital room for further recovery. Generally the EVD can remain in place for around 10-14 days. The ultimate goal is to remove the EVD when it is no longer needed. In some cases permanent CSF diversion is necessary which will require the placement of a Ventriculoperitoneal shunt. In cases where the EVD cannot be removed by 14 days and a shunt can’t be placed the EVD may need to be changed to reduce the risk of infection.