The EVD medical abbreviation usually means external ventricular drain, a thin tube that a neurosurgeon places through a small hole in the skull into one of the fluid filled spaces of the brain, so that cerebrospinal fluid can drain into a collection bag and pressure inside the head can be measured. It is used mainly in neurosurgical and neuro intensive care units.
In infectious disease and public health writing, EVD has a second meaning, Ebola virus disease. The setting nearly always makes the choice obvious. This page explains how an external ventricular drain works, what the numbers in a nursing note mean, and where the other meaning fits.
At a glance
How an external ventricular drain works
The brain sits in fluid that is made and absorbed all the time. When that flow is blocked, for example by bleeding or swelling, fluid can build up and pressure can rise. An EVD gives the fluid a way out. The tube runs from a ventricle, through the skull and scalp, to a drip chamber and bag hung on a pole beside the bed.
The height of the drip chamber controls how easily fluid drains. Staff level the system to a landmark on the head, often near the ear, and the doctor orders a set height in centimeters of water. Raising the chamber makes drainage harder, lowering it makes drainage easier. The same system connects to a monitor that shows intracranial pressure.
Reading an EVD medical abbreviation note in the ICU
Neuro ICU nurses check and chart the drain at least hourly. A typical entry looks like this.
| Entry | Meaning |
|---|---|
| EVD open | The drain is allowed to flow, not clamped |
| at 10 cm H2O | Drip chamber height ordered by the doctor |
| above tragus | Measured from a point at the front of the ear |
| ICP 12 | Intracranial pressure reading in mm Hg |
| CSF blood tinged | Fluid has a pink or red tint, common after bleeding |
Hospitals and units set their own targets for pressure and drainage, so the numbers in one chart cannot be judged against another.
Bedside handoff: "EVD clamped for the scan, reopen and relevel when back." The drain is closed during transport so fluid does not drain too fast when the bed moves, and it will be reopened and leveled on return. This shows usage, not a protocol.
Why an EVD is placed
Common reasons include hydrocephalus, a buildup of fluid in the ventricles; bleeding into the ventricles, charted as IVH; bleeding around the brain from a ruptured aneurysm, written SAH; and severe head injury, or TBI. The drain is temporary. When the brain can manage its own fluid again, the team may clamp it for a trial and then remove it, or place a permanent shunt if needed.
Because the drain opens a path into the brain, infection prevention is a major focus, with careful dressing care and limits on opening the system.
EVD as Ebola virus disease
Global health agencies, including the World Health Organization, use EVD for Ebola virus disease, a severe viral illness seen in outbreaks. In that setting the letters appear in outbreak reports, travel screening forms and infection control plans, not in neurosurgical notes.
| Clue in the record | Likely meaning |
|---|---|
| Drain height, ICP, CSF output | External ventricular drain |
| Outbreak, exposure, isolation | Ebola virus disease |
Frequently asked questions
What does EVD stand for in the ICU?
In the ICU EVD stands for external ventricular drain. It drains fluid from the brain into a bag outside the body and lets staff measure the pressure inside the skull.
Is an EVD the same as a shunt?
No. An EVD is temporary and drains to a bag outside the body. A shunt is placed fully under the skin and drains fluid to another body area, usually the abdomen, for long term use.
Why is an EVD clamped sometimes?
Teams clamp the drain during moves, position changes or trials to see if the brain can manage fluid on its own. Each unit follows its own procedure for this.
What does EVD mean in an outbreak report?
In public health and infectious disease reports EVD means Ebola virus disease. It is unrelated to the brain drain used in neurosurgery.