External Ventricular Drain (EVD)
What is an EVD?
“EVD” stands for external ventricular (ven-TRICK-you-ler) drain. It is a small tube. Some people have an increase of fluid in the brain. The extra fluid puts pressure on the brain. This is called intracranial (in-truh-KRAY-nee-ol) pressure. To reduce the pressure, the doctor can insert an EVD into the brain to drain the extra fluid. The part of the brain where the tube is placed is called the ventricle (VEN-trick-ol).
How does an EVD work?
The fluid flows from the brain, through the EVD, and into a bag. The bag hangs on the head of the patient’s bed or on an IV (intravenous) pole. The doctor and nurse check how much fluid drains into the bag. The EVD has a device that helps measure pressure in the brain as fluid drains. It lets the doctor and nurse know if the extra pressure is decreasing. The EVD is used for a period of time and then is removed.
When is an EVD needed?
Too much pressure in the brain may cause symptoms. When a patient has symptoms, an EVD may be needed. Symptoms may include:
- Nausea and vomiting
- Becoming less alert or less awake
What causes extra brain fluid?
An increase of brain fluid may occur with the following conditions:
- A bulge in a blood vessel (aneurysm) that breaks open
- A tumor
- A stroke
- A serious head injury
What precautions are needed?
The patient must do exactly what the doctor or nurse says about changing position. This is very important. A patient who has an EVD:
- Must never get out of bed without calling the nurse, even to go to the bathroom
- Must call the nurse for help to change the bed position. This includes moving the head of the bed up or down.
Note: Changing position without help can cause serious harm to the patient.
Can there be problems?
Sometimes other problems can result from a procedure. These problems are called complications. With an EVD, some possible problems are:
- Bleeding inside the brain or where the tube enters the head
- Infection of the brain fluid or of the brain itself
The doctor and nurse watch closely for signs of infection. The patient’s temperature is checked often. Brain fluid samples are tested in the lab frequently.