External Ventricular Drain

Introduction

An external ventricular drain (EVD) is a soft catheter that is inserted via a burr hole into the anterior horn of the lateral ventricle and connected to a closed sterile system to allow for temporary drainage of cerebrospinal fluid (CSF) and/or monitoring of intracranial pressure

Indications for external ventricular drainage are:

• To relieve raised intracranial pressure

• To divert infected CSF

• To divert bloodstained CSF following neurosurgery/haemorrhage

• To divert the flow of CSF

• To monitor intracranial pressure

Normal production of CSF

EVD output is variable and production increases with age. Usual rates⁶:

Medical staff should be alerted when there is any significant increase in the hourly drainage volume or drainage exceeds the parameters set by the neurosurgeon.

Ensure serum electrolytes are measured daily. Significant losses may need to be replaced in some children/infants.

Normal characteristics of CSF

External ventricular drainage system

Alignment and setting height of the external ventricular drain.

The drain management is prescribed by the medical staff and is documented on the CSF Drainage Record (CR4023).

The zero reference point for an EVD is level with the Intraventricular Foramen (Foramen of Munro), located at the beginning of the third ventricle.

The external anatomical reference points which correspond most closely to the position of the intraventricular foramen are the external auditory meatus (EAM), or ear canal, when the patient is supine or sitting up, or the bridge of the nose, if the patient is lying on their side.

Correct alignment is important for accurate pressure monitoring and control of CSF drainage:

• Use a spirit level to ensure the main system stopcock on the drainage system (zero point) is level with the relevant anatomical reference point

• Position the pressure level arrow at the top of the flow chamber at the prescribed height on the appropriate scale

• pressure is usually prescribed in cmH₂O however if the pressure is transduced it will be displayed in mmHg

• The collection system must be securely attached to a dedicated pole. Tape the hanging cord for added security

• When changing the patient’s position or altering the height of the bed, or if a child is crying excessively ensure that the stopcocks are closed. The system is then realigned and the stopcocks re-opened

• The drain should never be clamped for longer than 1 hour except for PICU patients on the Traumatic Brain Injury protocol, and less if the CSF is heavily bloodstained. Increased observation is important whilst clamped.

• Ensure that the parents/caregivers know to contact a nurse before moving the child (eg lifting out of bed)

• An RN competent at caring for a patient with an EVD is required to escort patients transferred within the hospital

• The drip chamber must be emptied and the EVD clamped before the EVD is placed horizontally on the bed to ensure the filter does not get wet which can affect drainage efficiency

Connecting the drainage system to external monitoring

Equipment required:

• Aseptic field (trolley or tray)

• Sterile gloves

• 50mL syringe with sodium chloride 0.9% for IV use

• Combi lock

• Pressure transducer set with bag spike removed

• Transducer mount

• Pressure transducer cable for the monitor

Prepare the system :

1. Prime the transducer system with sterile sodium chloride 0.9%

2. Verify absence of leaks and air bubbles

3. Disconnect flush syringe from pressure tubing and replace with sterile combi lock

4. Attach pressure tubing and transducer to EVD main system 3 way tap (red port)

5. Attach transducer to the monitor cable

6. Attach the monitor cable to the monitor

Zero the ICP transducer:

1. Align the pressure transducer with the zero level on the drainage system and patient landmark (as above)

2. Turn the main system 3 way tap off to the patient

3. Open the transducer 3 way tap to air (remove cap)

4. Press the zero button on the monitor screen

5. Close the transducer 3 way tap to air (replace cap)

6. Open the main system 3 way tap to the patient and verify presence of ICP wave form

Set the height of the EVD by sliding the drip chamber arrow to the desired pressure setting as prescribed (cmH₂O)

Clinical requirements

There are three different clinical requirements within paediatrics:

Continuous drainage with no monitoring

The main system 3 way tap is off to the red cap and open between the patient and flow chamber. The difference in height between the child’s ventricles and the drip chamber creates both a pressure gradient and a safety valve. The height of the drip chamber equates intracranial pressure (ICP). This pressure must be reached before any CSF will drain into the drip chamber.

Continuous drainage with monitoring

The main system 3 way tap is open to both allow CSF to flow from the patient to the flow chamber (as described above) and to allow ICP monitoring.

The ICP waveform will be dampened with continuous drainage so the 3 way tap must be turned off to drainage to measure and record an accurate ICP at least hourly.

Continuous monitoring with intermittent drainage

The main 3 way tap to the flow chamber is closed and the patient line is open to transmit the ICP from the ventricles to the transducer

When ICP exceeds the ordered parameter, CSF should be drained by turning the main 3 way tap off to the pressure transducer and open to drainage.

• For PICU patients refer to first tier interventions for raised ICP

• For other patients, refer to neurosurgical instructions.

Nursing assessment

Neurological and clinical assessment:

Observations should be done as per observation and monitoring guideline.

Hourly EVD assessment:

• Check the height of drip chamber and drainage limits for the EVD. The height for the drain should not be altered without discussion with the neurosurgical team UNLESS the neurosurgeon has indicated that a specific amount of CSF should be drained each hour. ONLY then should a nurse change the drain height independently.

• Record the amount of CSF drainage. Ensure slide clamp below flow chamber is closed to obtain hourly measure of CSF drainage. Empty fluid into collection bag each hour.

• Document the colour and appearance of CSF.

• Assess for under-drainage of CSF:

  • Bulging of fontanelle in infants

  • Headaches

  • Vomiting

  • Irritability

  • Lethargy

• Assess for over-drainage of CSF:

  • Sinking of fontanelle in infants

  • Headaches

  • Irritability

  • Pallor

  • Tachycardia

• Check the patency of the system – oscillation of CSF.

• Check catheter secure and dressing intact

Medical staff should be alerted:

• immediately if there are any changes in conscious level, neurological deficits or signs of raised intracranial pressure

• if there is a significant increase in the hourly drainage volume

• if drainage exceeds the parameters set by the neurosurgeon

• if there is no drainage or if EVD not patent (see Troubleshooting - no CSF below)

• if there are any signs of infection

  • Pyrexia

  • Change in level of consciousness

  • Evidence of meningism

  • Neck stiffness or Kernig's sign

  • Headache, vomiting, photophobia, lethargy, irritability, confusion, anorexia

  • Changes in CSF appearance

  • Exudate at EVD insertion site

• if there is a CSF leak

• if the system is inadvertently disconnected

• if the catheter is inadvertently removed

• if the patient has rhinorrhoea or CSF trickle at the back of their throat

EVD site care

• The post op dressing should be changed at 24 hours (if necessary) using ANTT and alcohol 70% wipes to clean the site. The EVD should be looped and secured and covered with a sterile occlusive dressing (e.g. primapore®)

• Following this the dressing should be changed weekly or more often if soiled.

Trouble shooting

• If there is no CSF in chamber:

  • Observe for oscillation of CSF in tubing

  • Ensure tubing is not clamped or kinked

  • Lower chamber momentarily below head level & observe for CSF movement. Advise medical team if no drainage

• If a catheter appears to be blocked:

  • Exclude damage to the EVD system

  • Momentarily lower chamber and observe for CSF movement

  • If the EVD will still not drain then this constitutes a neurosurgical emergency and the neurosurgeon on call must be contacted urgently. Medical staff may attempt to aspirate the catheter. If aspiration is unsuccessful the EVD should be flushed. Aspiration and flushing are outside the scope of RN practice and must only be done by medical staff.

  • If the EVD continues to not drain the child may need to return to theatre for a new drain and requires close observation during this time.

• If there is an accidental disconnection of the system:

  • Turn stopcock closest to patient off and clamp tubing with sterile forceps or blue plastic clamps

  • Assess and monitor neurological status

  • Notify medical team immediately

• If the catheter is accidentally removed:

  • Apply sterile dressing to the site and assess for CSF drainage on dressing.

  • Assess and monitor neurological status

  • Notify medical staff immediately

  • Site may need to be sutured and/or patient prepared for reinsertion of EVD

• Planned removal of the EVD is undertaken by medical staff only as a suture is required post removal.

CSF Specimens

CSF samples are taken only if directed by medical staff.

The external ventricular catheter should never be aspirated as this can cause ventricular bleeding and neurological damage.

Follow the steps below to safely and effectively obtain a sample of cerebrospinal fluid (CSF):

Equipment required

• Aseptic field

• Non sterile gloves

• 70% alcohol wipes

• Sterile CSF container (black top bottle x1 comes in packs of 3 – must open a sterile pack each time).

• 25 gauge needle

Steps

1. Turn the 3 way tap nearest the patient off to the drainage system while collecting equipment.
   

   

2. Clean the injection port on the 3 way tap with 70% alcohol wipe and allow to dry.

3. Insert 25 gauge needle bevel up into injection port with other end situated over the open CSF collection bottle. Open the 3 way tap and allow CSF to drip passively into the container.

4. Ensure at least 10-20 drops of CSF are obtained or as per specimen requirements

5. Allow up to 5 minutes to collect the specimen. If not able to collect sufficient sample, stop procedure and discuss with medical staff.

6. Turn the 3 way tap off to the needle.

7. The labelled specimen is sent for microbiology culture and sensitivity and other tests as specifically requested.

8. Document the procedure on the EVD chart

If the injection port has been removed a blue combi-lock will be in situ.

Steps to obtain a specimen:

1. Turn the 3 way tap nearest the patient off to the drainage system while collecting equipment.

2. Remove the combi lock.

3. Clean the 3 way tap with 70% alcohol wipe and allow to dry.

4. Place open CSF collection bottle under the open end of the 3-way tap.

5. Ensure at least 10-20 drops of CSF are obtained or as per specimen requirements.

6. Allow up to 5 minutes to collect the specimen. If not able to collect sufficient sample, stop procedure and discuss with medical staff.

7. Turn the 3 way tap off to the open end.

8. Place new blue combi lock.

9. The labelled specimen is sent for microbiology culture and sensitivity and other tests as specifically requested.

10. Document the procedure on the EVD chart

Changing the EVD bag

Follow the steps below to safely change the EVD system bag .

The drainage bag should be changed when it is about three quarters full as overfilling the drainage bag may impair drainage .

Equipment required:

Collect the following equipment :

• Aseptic field

• Gloves

• 70% alcohol wipe

• Sterile drainage bag

Steps:

1. Close the 2 slide clamps between the drip chamber and the collection bag

2. Clean the connection with 70% alcohol wipes and allow to dry

3. Disconnect bag and replace with new bag

4. Seal the old collection bag with the spare cap from the new bag and dispose in the medical waste bin.