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Lumbar puncture

  • See also

    CSF Interpretation
    LP Parent Handout


    Lumbar puncture may be performed as part of the initial work up of a sick child, or later in the course of an illness once the child has stabilised if there were initial contraindications. It is preferable to obtain a CSF specimen prior to antibiotic administration, however this should not be unduly delayed in a child with signs of meningitis or sepsis.

    You must always discuss with a senior registrar or consultant before doing a lumbar puncture.



    You must always discuss with a senior registrar or consultant before doing a lumbar puncture.

    Do not do a lumbar puncture if the child is so sick that you will give antibiotics for meningitis even if the CSF is normal on microscopy. 

    The clinical findings that suggest you should give dexamethasone and antibiotics immediately, and delay lumbar puncture for 1-2 days until the child is improving are:

    • Coma: absent or non-purposeful response to painful stimulus - squeeze ear-lobe firmly for up to 10 seconds. A child over 3 months of age should push you away and seek a parent
    • Signs of raised intracranial pressure: eg drowsy, diplopia, abnormal pupillary responses, unilateral or bilateral motor posturing or papilloedema (NB papilloedema is an unreliable and late sign of raised ICP in meningitis; a bulging fontanelle in the absence of other signs of raised ICP, is not a contraindication)
    • Cardiovascular compromise / shock
    • Respiratory compromise
    • Focal neurological signs or seizures
    • Recent seizures (within 30 minutes or not regained normal conscious level afterwards)
    • Coagulopathy / thrombocytopenia
    • Local infection (in the area where an LP would be performed)
    • The febrile child with purpura where meningococcal infection is suspected
    Assessment prior to LP for contraindications?
    • CT Scans if focal neurological signs
      • CT Scans are not helpful in most children with meningitis
      • A normal CT scan does not tell you that the patient does not have raised ICP
      • Herniation may occur even in the presence of a normal scan
      • Don't delay antibiotics whilst waiting for a CT  


    Informed verbal consent should be obtained. This should include a discussion of the benefits of the procedure in terms of possible diagnoses and potential complications. Complications of LP may include:

    • Failure to obtain a specimen / need to repeat LP / Traumatic tap (common)
    • Post-dural puncture headache (fairly common) - up to 5-15%
    • Transient/persistent paresthesiae / numbness (very uncommon)
    • Respiratory arrest from positioning (rare)
    • Spinal haematoma or abscess (very rare)
    • Tonsillar herniation (extremely rare in the absence of contraindications above)

    The LP Parent Information Sheet may be useful in talking to parents about the procedure. ( See below)

    Analgesia, anaesthesia and sedation

    • Non-pharmacological techniques should be used where possible, including explanation (in an older child), distraction, and the presence of a parent.
    • All children should have some form of local anaesthetic for lumbar puncture.
      • Use topical anaesthetic cream (AnGEL) except where specimens are required urgently
      • Subcutaneous lignocaine should be used in addition to topical anaesthetic.
        • Up to 0.4 mL/kg of 1% (4 mg/kg)
    • Oral Sucrose should be used for infants <3 months (see Analgesia & sedation)
    • Sedation, including nitrous, should be considered for children older than 6 months with normal conscious state.


    • Monitor all sedated or seriously ill children with continuous pulse oximetry +/- ECG leads.


    • At least one trained assistant to hold the child
    • Sterile gloves
    • Sterile drapes and procedure tray
    • Skin preparation: povidone iodine solution (Betadine) or chlorhexidine
    • Local anaesthetic lignocaine, 2 mL syringe, 25G needle
    • CSF tubes (2)
    • Spinal needle (see below)
    • NB Spinal manometry is not routinely performed in children during lumbar puncture.

    Spinal Needles

    • 22G or 25G bevelled spinal needles with stylet (the use of needles without a stylet has an associated risk (rare) of spinal epidermoid tumours)
      • see Spinal needles for a guide to needle size and insertion distance
    • Consider 25G pencil point needles for older children/adolescents (eg Whitacre 25G 5 cm, 9 cm available in ED at RCH)
      • Pencil-point (blunt) needles reduce the risk of headache in adults, however the evidence is not convincing in children.


    The most important determinant of a successful lumbar puncture is a strong, calm, experienced assistant to hold the patient. Position of the patient is critical.


    • Lumbar puncture may be performed with the child lying on their side or sitting up.
    • Aim for maximum flexion of the spine (curl into fetal position), but avoid over flexing the neck, especially in infants as this may cause respiratory compromise. Ask an adolescent to slouch rather than bend from their hips.
    • Ensure that the plane of the back is exactly at 90 degrees to the bed (ie. not leaning towards or away from you). Make sure the hips and shoulders are in line
    • 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)
      • The conus medullaris finishes near L3 at birth, but at L1-2 by adulthood
      • Aim for the L3-4 or L4-5 interspace


    • Wash hands and aseptically put on sterile gloves
    • Prepare the skin with povidone-iodine or chlorhexidine and set up sterile drapes
    • Allow adequate time for the skin preparation to dry
    • Take the tops off the tubes, ensuring that they remain sterile
    • Infiltrate the skin with 1% lignocaine using a 25G needle

    Lumbar Puncture:

    • Position the needle in the midline with the bevel pointing towards the ceiling (lateral decubitus position) or to the side (sitting)
    • Pierce the skin with the needle and pause. Wait for the child to stop wriggling
    • Reorientate (ensure that back is vertical, needle is parallel to the bed and perpendicular to the back). Aim for the umbilicus (ie slightly cephalad)
    • Advance the needle into the spinous ligament (increased resistance). Continue to advance the needle within the ligament until there is a fall in resistance. Remove the stylet. If CSF is not obtained replace the stylet and advance the needle slightly then recheck for CSF
      • An alternative technique is to remove the stylet once the needle is in the ligament and advance very slowly without stylet watching for CSF to flow back. This has the advantage of making it harder to go unintentionally past the subarachnoid space
      • If the needle meets resistance, withdraw the needle slowly whilst watching for CSF. If none is obtained, replace the stylet, re-orient the needle and re-try
      • If blood stained fluid is obtained collect some for culture. If it clears it can be used for a cell count. If it fails to clear another attempt at a different level may be required
      • See Spinal needles for a guide to insertion distance
    • If CSF is flowing, collect into 2 numbered sterile tubes (5-10 drops each is usually adequate)
    • Replace the stylet (this may reduce risk of headache), and remove the needle and stylet
    • Apply brief pressure to the puncture site
    • Send specimens urgently to the lab for microscopy, protein, glucose, culture. (NB CSF glucose estimation is most useful if there is a synchronous plasma glucose). see CSF Interpretation

    Post-procedure care

    Cover the puncture site with a band-aid or occlusive dressing (eg Tegaderm)
    Bed-rest following lumbar puncture is of no benefit in preventing headache in children.


    Parent Information Sheet (Print version - PDF)
    Parent Information Sheet (HTML version)