See also

Meningitis and encephalitis
CSF interpretation

Key points

1. A lumbar puncture (LP) should only be performed after a thorough neurological examination and once all contraindications have been considered
2. Performing LP should never delay life-saving interventions such as antibiotics
3. A normal CT scan does not exclude raised intracranial pressure
4. Careful preparation, adequate analgesia and an experienced assistant are critical to success

Background

• LP is performed at or below the L4 level
• The conus medullaris finishes near L3 at birth, but at L1-2 by adulthood
• The decision to perform LP should generally be discussed with a senior clinician
• It is preferable to obtain a CSF specimen prior to antibiotic administration; however, antibiotics must not be unduly delayed in a child with signs of meningitis or sepsis
• In a child with fever and purpura, in whom meningococcal infection is suspected, LP may not change the management and may cause deterioration
• In term infants, the seated position has been shown to be the best tolerated and to also have the best chance of obtaining CSF
• If an LP is unsuccessful on two occasions, refer to a senior colleague, reassess the need for LP and consider image guidance to assist
• CT scans are not helpful in most children with meningitis; a normal CT scan does not exclude raised intracranial pressure (ICP) and brain herniation may occur even in the presence of a normal CT scan

Assessment

Indications

• Suspected meningitis or encephalitis
• Suspected sub-arachnoid haemorrhage with a normal CT
• Diagnosis, monitoring and treatment (using intrathecal medications) of a range of haematological, malignant and neurological disorders

Contraindications

• GCS <8 or deteriorating/fluctuating level of consciousness
• Signs of raised intracranial pressure (ICP): diplopia, abnormal pupillary responses, decerebrate or decorticate posture, low HR + elevated BP + irregular respirations, papilloedema
• A bulging fontanelle in the absence of other signs of raised ICP is not a contraindication

• Septic shock or haemodynamic compromise
• Significant respiratory compromise (eg apnoeas in a baby)
• New focal neurological signs or seizures
• Seizure within previous 30 min +/- normal conscious level has not returned following a seizure
• INR >1.5 or platelets <50 or child on anticoagulant medication

Complications

• Failure to obtain a specimen/traumatic bloody tap (common)
• Post-dural puncture headache (uncommon) 5-15%
• Transient/persistent paraesthesia/numbness (very uncommon)
• Respiratory arrest from positioning (rare)
• Infection introduced by needle causing meningitis, epidural abscess or osteomyelitis (very rare)
• Spinal haematoma (very rare)
• Brain herniation (extremely rare in the absence of contraindications above)

Procedure

Staff

• Doctor
• At least one trained assistant to hold the child

Equipment

• Sterile gloves
• Sterile drapes and procedure tray
• Skin preparation: povidone iodine solution (Betadine^®) or 2% chlorhexidine + 70% isopropyl alcohol. In neonates and extremely premature babies, use specialised solutions in order to avoid burning the skin
• Local anaesthetic 1% lignocaine, 2 mL syringe, spinal needle
• CSF tubes
• Spinal needle of appropriate length
• Spinal manometer is not required unless monitoring CSF pressure

Spinal needles

• Use a 22 or 25 gauge bevelled spinal needle with stylet (the use of needles without a stylet has an associated rare risk of spinal epidermoid tumours)
• Consider using 25 gauge pencil point needles for older children/adolescents to reduce the risk of headache; evidence is not convincing in younger children

Median spinal cord depth has been correlated with weight
Neonates & infants (mm) = 2 x wt (kg) + 7, children (mm) = 0.4 x wt (kg) + 20

Analgesia

• Acute pain management including non-pharmacological techniques
• Child Life Therapy services where appropriate and available
• Local anaesthetic if possible
  
  • Topical anaesthetic cream (EMLA^® or AnGEL^®) for 45-60 minutes prior, except where specimens are required urgently
  • Subcutaneous 1% lidocaine (lignocaine) max 4 mg/kg
    
• Oral sucrose should be used for infants <3 months
• Nitrous oxide should be considered for children >12 months (or younger with senior clinician involvement)
• Other sedation should be discussed with a senior clinician

Monitoring

• Cardiorespiratory and oxygen saturation monitoring

Position

• Lumbar puncture may be performed with the child lying on their side or sitting up
• Position back and bottom close to edge of bed
• Aim for maximum flexion of spine (curl into foetal position), but avoid over-flexing neck, especially in infants, as this may cause respiratory compromise
• Position plane of the back at 90 degrees to the bed and make sure hips and shoulders are square with each other
• Draw an imaginary line between the top of the iliac crests. This intersects the spine at approximately the L3-4 interspace (mark this if necessary)
• Aim for the L3-4 or L4-5 interspace

Preparation

• Informed consent should be obtained and documented. This should include a discussion of the benefits of the procedure in terms of possible diagnoses and potential complications. The parent LP information sheet is useful when talking to parents about the procedure
• Put on mask
• Wash hands and aseptically put on sterile gloves ± gown
• Prepare skin and set up sterile drapes
• Allow adequate time for skin preparation to dry
• Take tops off tubes, ensuring that they remain sterile
• Infiltrate skin with 1% lignocaine using a 25 gauge needle

Lumbar puncture

• Position needle in midline, with bevel pointing towards ceiling (if child lying) or to the side (if child sitting)
• Pierce skin with needle and pause to ensure child is still
• Check child's position and adjust if necessary
• Angle needle aiming for umbilicus
• Advance needle into spinous ligament, where there will be increased resistance
• Continue to advance needle slowly within ligament until there is a fall in resistance (this may not be obvious in neonates)
• Firm resistance and inability to advance needle is likely due to bony obstruction requiring withdrawal and repositioning of needle
• Remove stylet
• If CSF is flowing:
  • collect into 2-3 numbered sterile tubes
  • 5-10 drops in each is usually adequate, but more may be required depending on investigations ordered. 20 drops = 1 mL
• If CSF is flowing very slowly, rotate needle 90°
• If blood-stained fluid is flowing:
  • collect some for culture. If it "clears", it can be used for a cell count, which is best performed on final tube collected
  • consider whether blood may be due to sub-arachnoid haemorrhage
  • if it does not "clear", another attempt at a different level may be required
• If CSF is not flowing:
  • replace the stylet and advance (or withdraw and reposition) the needle slightly, then re-check for CSF
  • it is possible to reposition and reangle needle multiple times, each time reviewing patient and needle position
  • multiple attempts may lead to local swelling and bruising
• After CSF collection or failed attempt:
  • replace stylet (this may reduce risk of headache), and remove needle and stylet together
  • apply brief pressure to puncture site
• Send specimens urgently to lab; proper interpretation of CSF glucose requires paired blood glucose level to be collected

Post procedure care

• Cover puncture site with a band-aid or occlusive dressing
• Bed-rest following LP is of no benefit in preventing headache in children
• Perform further vital sign and neurological observations as indicated by sedation used and child's clinical state
• Document in patient record
• analgesia and anaesthetic use
• needle length and gauge
• number of attempts required
• description of CSF appearance

Consider consultation with local paediatric team when

Unsure whether LP should be performed

Consider transfer when

Child is unwell above the comfort level of the hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services.

Consider discharge when

Parent information

Last updated October 2020