Neurosurgical emergency · UK
External ventricular drain (EVD) — a patient and family guide.
An EVD is an emergency neurosurgical procedure. A thin catheter is placed into a fluid-filled ventricle in the brain to drain cerebrospinal fluid and measure pressure inside the skull. It is a bridge — to recovery, or to a definitive shunt.
Why families choose us
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A neurosurgical team, not a queue
An EVD is an emergency. Your family gets a named consultant neurosurgeon and an ITU team who explain what is happening, in plain words.
- 02
A proper aseptic bundle
Antibiotic-impregnated catheter, tunnelled exit, closed drainage system, and a strict sampling protocol — the details that keep ventriculitis rates down.
- 03
Independent, and free
We are paid by no hospital, so the recommendation is impartial and costs the family nothing.
The key numbers
What the ITU team is looking at, in numbers.
The figures the neurosurgical team and the ITU nurse are watching at the bedside — so a family reading the chart has a chance of following it.
In short
A drain typically in for 5–14 days, levelled 10–20 cmH₂O above the tragus.
| Parameter | Typical value | Setting | Monitoring |
|---|---|---|---|
| Insertion typical dwell time | 5–14 days | ITU stay | Continuous |
| Catheter position (from Kocher’s point) | 5–6 cm depth | Frontal horn | CT-confirmed |
| Drain level above tragus | 10–20 cmH₂O | Set by team | Reviewed hourly |
| Target CSF drainage | 5–15 mL/hour | Or gravity | Charted hourly |
| Ventriculitis rate (published) | ≈5–15% | Duration-dependent | Minimised by bundle |
| Antibiotic-impregnated catheter | Rifampicin/clindamycin | First choice | Where available |
These are typical adult figures from UK neurosurgical ITU practice. The exact numbers depend on the patient, the pathology, and unit protocol — they should be set and reviewed by the treating team.
The problem
The right hands, the right catheter, the right bundle.
An EVD is straightforward to describe and unforgiving in practice. Infection rates track with technique — the aseptic bundle, the catheter type, and the discipline of the ITU team.
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Is it definitely needed?
For a small IVH or mild hydrocephalus, close observation and medical management may be enough. A neurosurgeon should confirm the indication.
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Bedside or theatre?
Unstable, ventilated patients are usually done at the bedside on ITU. Anticipated difficulty or combined procedures move to theatre.
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What next after the EVD?
Wean, or convert to a permanent VP/VA shunt or an ETV. The plan should be set on the day the drain goes in.
The journey
From CT scan to weaning — what happens, in order.
One neurosurgical team from decision to weaning, working with the ITU consultant and nursing team at the bedside.
Phase 1 · Before insertion
Confirming the indication
Phase 2 · Insertion
Bedside or theatre
Phase 3 · ITU management
Monitor, sample, wean
- 01
Before
The clinical picture is confirmed
CT or MRI shows acute hydrocephalus, intraventricular haemorrhage, or raised intracranial pressure. The neurosurgical team confirms an EVD is needed.
- 02
Before
Consent and preparation
A family member is talked through the risks and the alternatives. Clotting is checked, antiplatelets and anticoagulants are reviewed, and the scalp is prepped and clipped.
- 03
Before
Antibiotic prophylaxis
A single dose of intravenous antibiotic is given at induction, in line with unit policy. Nasal MSSA decolonisation is often used when time allows.
- 04
Insertion
Insertion at bedside or in theatre
Bedside on ITU under local, or in theatre under general anaesthetic. A small burr hole is made at Kocher’s point, 2–3 cm from the midline in front of the coronal suture.
- 05
Insertion
The catheter is passed and tunnelled
The catheter is passed 5–6 cm into the frontal horn of the lateral ventricle, then tunnelled under the scalp before it exits the skin, which lowers infection risk.
- 06
Insertion
The drain is set and levelled
The transducer is zeroed at the tragus. Drainage is set — usually 10–20 cmH₂O above the tragus — and continuous ICP is displayed at the bedside.
- 07
After
ITU monitoring, then weaning
Hourly neuro-observations, daily CSF sampling if suspected ventriculitis, and a weaning trial once the underlying cause has settled. Conversion to a shunt or ETV if drainage is still needed.
Typical dwell time: 5–14 days. Then wean, or convert to a VP/VA shunt or ETV.
When it helps
When an EVD is the right step.
The situations neurosurgical teams place an EVD for — and the red flag that means an emergency call rather than a family conversation.
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Acute obstructive hydrocephalus
CSF flow is blocked — usually by intraventricular haemorrhage, a posterior fossa tumour, or aqueduct occlusion. Pressure rises quickly.
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Subarachnoid haemorrhage
A ruptured aneurysm can cause acute hydrocephalus. An EVD relieves pressure and lets neurosurgery plan the definitive treatment.
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Traumatic brain injury
Where ICP is raised and the ventricles are visible, an EVD both measures pressure and treats it by draining CSF.
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Intraventricular haemorrhage
Blood in the ventricles blocks CSF drainage. An EVD is often the first, and sometimes life-saving, step.
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Post-neurosurgical CSF diversion
Temporary drainage after posterior fossa surgery, tumour resection, or infection, until a definitive plan is made.
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Meningitis with hydrocephalus
Infection can obstruct CSF flow. An EVD both diverts CSF and gives a route for daily CSF sampling.
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Bridge to shunt or ETV
An EVD is temporary. Most patients either wean off, or are converted to a permanent VP shunt or an endoscopic third ventriculostomy.
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Red flag: sudden GCS drop
A sudden fall in conscious level, a blown pupil, or Cushing’s response is an emergency — not a clinic conversation.
Procedure options
An EVD comes in variants — and it is not the only option.
What each option involves, when it is chosen, and what a permanent solution looks like once the acute phase is over.
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Bedside insertion (ITU)
Done under local anaesthetic on the intensive care unit. Preferred when the patient is unstable or already sedated and ventilated.
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Theatre insertion under GA
Done in an operating theatre with an anaesthetist. Preferred for anticipated difficulty or where combined procedures are planned.
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Antibiotic-impregnated catheter
A catheter coated with rifampicin and clindamycin. Reduces catheter-related infection compared with plain silicone.
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Tunnelled exit site
The catheter is tunnelled 5–10 cm under the scalp before exiting. Shown to reduce ventriculitis compared with a non-tunnelled drain.
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Closed CSF drainage system
A dedicated closed system with a burette, three-way tap and pressure transducer. Broken only for scheduled aseptic sampling.
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Bilateral EVD
Two drains, one in each lateral ventricle, occasionally needed when the third ventricle is blocked and cannot drain across.
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Conversion to VP or VA shunt
If CSF diversion is needed long term, the EVD is replaced by a permanent shunt to the peritoneum or the atrium.
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Endoscopic third ventriculostomy (ETV)
For selected obstructive hydrocephalus, ETV creates an internal bypass so a shunt can sometimes be avoided altogether.
Our vetted UK network
The standards we insist on, for a good reason.
Neurosurgical units are not interchangeable. Ventriculitis rates track with technique, staffing and discipline — these are the details we look for.
Selection criteria
How we choose every neurosurgical unit in our network.
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Consultant neurosurgeons, not trainees working unsupervised
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A dedicated neuro-ITU with hourly neuro-observation charting
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Antibiotic-impregnated catheters and a written aseptic insertion bundle
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A CSF sampling protocol with same-day microbiology reporting
Risks and expectations
What to expect at the bedside — honestly.
An EVD is a life-preserving intervention. It is also invasive, and it looks alarming to a family walking into ITU for the first time. Here is what to know.
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Ventriculitis is the main risk
Published infection rates run at 5–15% and rise with the number of days the drain stays in. Antibiotic-impregnated catheters, tunnelling and a strict aseptic bundle bring the rate down.
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Tract haemorrhage
Small bleeds along the catheter track are usually silent on CT. Rarely, in a patient on antithrombotic drugs, the bleed is catastrophic — which is why clotting is checked first.
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Catheter malposition or occlusion
The catheter can end up outside the ventricle, or block with clot or debris. A post-insertion CT confirms position; flushing is done only by the neurosurgical team.
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Over-drainage
Drainage that is too rapid can cause a subdural collection, slit-ventricle syndrome, or downward tonsillar herniation. This is why the drain level is set carefully and reviewed hourly.
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Pneumocephalus
Air can enter the ventricles during insertion or drain changes. Usually harmless and self-limiting; occasionally it needs the drain to be repositioned.
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Transient neurological worsening
A brief drop in GCS, a new seizure, or a headache after insertion can happen. The team examines, scans if needed, and adjusts drainage.
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Delirium and immobility
Prolonged bedrest in ITU brings its own risks — delirium, deconditioning, venous thromboembolism. VTE prophylaxis is used as soon as it is safe.
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Explaining it to family
An EVD is an emergency, life-preserving intervention. It looks alarming at the bedside; the ITU and neurosurgical team should sit with the family and walk them through it.
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Red flags after insertion
A new fever, cloudy CSF in the burette, a sudden change in ICP or GCS, or CSF leaking around the exit site all mean the team should reassess the drain the same shift.
Reading the daily notes
The operation note in four parts. Read the last one first.
Whichever unit does the case, the operation note keeps to the same shape. The plan at the end tells you what happens next.
A quiet reminder
Neurosurgical language is precise and can read coldly — we translate it for you.
If a family would like us to sit with them and talk through the notes, just ask.
- 01 Header
Indication and site
Why the EVD was placed — acute hydrocephalus, IVH, raised ICP after TBI — and which side and entry point were used.
- 02 Technique
Insertion, tunnel and catheter type
Bedside or theatre, local or GA, catheter type (antibiotic-impregnated or plain), tunnel length, and how many passes were needed.
- 03 Findings
CSF appearance and opening pressure
The colour of the CSF, whether it was under pressure, the opening ICP, and any samples that were sent for cell count, protein, glucose, Gram stain and culture.
- 04 Impression
Plan, drain level and weaning trigger
Read this first: the drain level, target hourly output, when to sample, the antibiotic plan, and the trigger for a weaning trial.
Recognised by major UK insurers
Most emergency neurosurgical care in the UK is delivered by the NHS. Where private cover applies, insurers typically fund it — we confirm cover before any elective conversion to a shunt or ETV.
Frequently asked
Everything families ask about an EVD.
Straight answers on what an EVD is, how long it stays in, and what happens after.
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What is an external ventricular drain and why is it done?
An EVD is a thin catheter placed into one of the fluid-filled ventricles in the brain to drain cerebrospinal fluid and measure the pressure inside the skull. It is used in emergencies — acute hydrocephalus, intraventricular haemorrhage, subarachnoid haemorrhage, traumatic brain injury with raised pressure, or meningitis with obstructed CSF flow.
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How is the drain inserted?
A small burr hole is made at Kocher’s point, about 2–3 cm from the midline just in front of the coronal suture, usually on the right. The catheter is passed 5–6 cm into the frontal horn of the lateral ventricle, then tunnelled under the scalp before exiting the skin. It is done at the bedside under local anaesthetic in ITU, or in a theatre under general anaesthetic.
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How long does the drain stay in?
Typically 5–14 days, sometimes less, occasionally longer. The team try to remove it as early as it is safe, because infection risk rises with time. Weaning involves raising the drain and clamping it in stages while checking the patient tolerates the pressure.
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What is the risk of infection?
Ventriculitis is the most feared complication. Published rates run at roughly 5–15% and are proportional to how long the drain stays in. Antibiotic-impregnated catheters, a tunnelled exit, a strict aseptic bundle, and CSF sampling only when clinically indicated all reduce the risk.
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Is prophylactic antibiotic given?
A single dose at induction is standard in most UK units. Ongoing prophylactic antibiotics for the whole time the drain is in are controversial — the DRAIN and VANCUVER trials showed no clear benefit and a real cost in antimicrobial resistance and Clostridioides difficile. Most units follow local policy.
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What happens after the EVD?
Most patients either wean off the drain as the underlying problem settles, or are converted to a permanent solution — a ventriculoperitoneal or ventriculoatrial shunt, or an endoscopic third ventriculostomy for selected obstructive hydrocephalus.
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What should the family expect at the bedside?
It looks alarming. There is a dressing on the scalp, a tube tunnelled behind the ear, and a burette hung from a stand at head height with fluid slowly dripping into it. The nurse checks it hourly. The ITU team should sit with the family and explain what the numbers mean.
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