Lumbar puncture

Indication

Suspected meningitis or encephalitis

Contraindications

Absolute

Blood culture++, then start antibiotics within one hour, and perform a scan before lumbar puncture if:

• Glasgow score <8 or deteriorating/fluctuating level of consciousness
• Signs of raised intracranial pressure: diplopia, abnormal pupillary responses, decerebrate or decorticate posture, low HR + elevated BP + irregular respirations, papilloedema

Relative

Blood cluture++, then start antibiotics within one hour, and lumbar puncture after patient stabilization:

• Septic shock or haemodynamic compromise
• Significant respiratory compromise eg apnoeic episodes
• New focal neurological signs or seizures
• Seizure within previous 30 mins and/or ongoing decreased conscious state following a seizure
• INR >1.5 or platelets <50 x 10⁹/L for child on anticoagulant medication

Analgesia

• Ensure acute pain management including non-pharmacological techniques
• Local anaesthetic if possible: ideally topical anaesthetic cream (EMLA®,AnGel®or LMX4®) for 45-60 minutes prior to LP, except where specimens are required urgently. Consider subcutaneous 1% lidocaine (max 4 mg/kg) for children >12 months.
• Use oral sucrose for infants
• Consider nitrous oxide for children >12 months (or younger with senior clinician involvement) note this may affect opening pressures if manometry required
• Other sedation should be discussed with a senior clinician

Monitoring

Cardiorespiratory and oxygen saturation monitoring

Position

• Keep neonate or infant under warmer
• LP may be performed with the child sitting up or lying on their side (with proceduralist’s dominant hand at caudal end)
• Position back and bottom close to edge of bed
• Aim for maximum flexion of spine (curl into fetal position), but avoid over-flexing neck, especially in infants, as this may cause airway obstruction and respiratory compromise
• Position plane of the back at 90° to the bed and make sure hips and shoulders are in line 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

• Obtain and document parental consent. This should include a discussion of the benefits of the procedure in terms of possible diagnoses, and potential complications
• Remove topical anaesthetic cream
• Proper interpretation of CSF glucose requires paired blood glucose level to be collected. Ideally, collect the blood glucose prior to LP
• 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% lidocaine using a 25-30G needle (smaller needle is less painful, but increases difficulty of infiltration) if local anaesthetic appropriate

Lumbar puncture

• Position needle in midline, with bevel pointing to the side if child sitting, or towards ceiling if child lying
• 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
• Firm resistance and inability to advance needle is likely due to bony obstruction and requires withdrawal and repositioning of needle; change the needle if bloody
• Continue to advance needle slowly within ligament until there is a fall in resistance (this may not be obvious in neonates)
• Remove stylet

If CSF is flowing collect:

• collect 2-4 numbered sterile tubes
• 10 drops in each is usually adequate, but more may be required depending on investigations ordered (10 drops = 0.5 mL)

If CSF is flowing very slowly:

• rotate needle 90 degrees

If blood-stained fluid is flowing:

• collect some for culture, if fluid “clears”, it can be used for a cell count, which is best performed on final tube collected
• consider whether blood may be due to subarachnoid haemorrhage

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 position of child and needle position
• Multiple attempts may lead to local swelling and bruising
• After CSF collection or failed attempt replace stylet (to reduce risk of headache), remove needle and stylet together and apply brief pressure to puncture site
• Send specimens urgently to lab

Post procedure care

• Cover puncture site with occlusive dressing
• Bed-rest following LP is of no benefit in preventing headache in children
• Perform further vital signs and neurological observations as indicated by sedation used and child’s clinical state
• Document in patient record:

• Patient record
• Analgesia and anaesthetic use
• Needle length and gauge
• Number of attempts required
• Description of CSF appearance

Preparation

• Position the patient in the lateral decubitus position, ensuring the spinal column is aligned horizontally
• Just after the ponction, when LCR can be collected, first connect the LP needle to a transparent tubing system (e.g., an IV tubing or similar sterile system)

Set-up

• Ensure the tubing is filled with sterile fluid to prevent air bubbles
• Elevate the distal end of the tubing vertically and secure it in place
• The tubing should be free to allow CSF to rise naturally

Measuring CSF pressure

• Observe the CSF as it rises in the tubing after lumbar puncture
• Wait until the CSF column stabilizes to account for natural fluctuations due to respiratory and cardiac cycles
• Measure the height of the CSF column in the tubing using a ruler or a marked scale
• The measurement is taken in centimeters (cm) from the point of the needle entry at the lumbar site

Converting to pressure

• CSF pressure is typically reported in cmH₂O (centimeters of water pressure)
• The height of the CSF column in cm directly corresponds to the intracranial pressure in cmH₂O (for example, a height of 10 cm in the tubing equals 10 cmH₂O)
• Normal opening pressure ranges (may vary depending on clinical factors):

• Opening pressure ranges
• Infants and young children: 3 to 7 cmH₂O
• Older children: 4 to 10 cmH₂O
• Adolescents: 5 to 15 cmH₂O
• Adults:6 to 25 cmH₂O

Considerations

• Ensure the patient is relaxed, as muscle tension or coughing may artificially elevate the pressure reading

• Sterile gloves
• Sterile drapes and procedure tray
• Skin preparation: 2% chlorhexidine + 70% isopropyl alcohol or povidone iodine solution (Betadine®). In neonates and extremely premature babies, use specialised solutions to avoid burning the skin eg 0.1% chlorhexidine
• Local anaesthetic 1% lidocaine, 2 mL syringe and 25-30G needle if local infiltration indicated
• Spinal needle of appropriate length
• Sterile CSF tubes
• Spinal manometer and three-way tap if opening pressures are required (e.g. cryptococcal meningitidis)

• The decision to perform a lumbar puncture (LP) should be discussed with a senior clinician
• In a seriously unwell child, prioritise urgent antibiotic administration over performing LP (It is preferable to obtain a CSF specimen prior to antibiotic administration. However, antibiotics must not be delayed more than 30 minutes in a child with signs of meningitis or sepsis)
• LP should only be performed after a thorough neurological examination and once contraindications have been considered
• Careful preparation, adequate analgesia/anaesthetic/sedation and an experienced assistant are key to success