Please note that all guidance is currently under review and some may be out of date. We recommend that you also refer to more contemporaneous evidence in the interim.
Lumbar puncture to sample cerebrospinal fluid (CSF) may be a necessary component of investigating an unwell neonate.
Investigations performed on CSF include:
- microscopy and culture to confirm or exclude evidence of bacterial, viral or fungal infection
- biochemical analysis to measure protein and sugar levels, or markers of a metabolic disorder.
In some cases of post haemorrhagic hydrocephalus, therapeutic tap may be required to limit ventricular dilatation (serial taps may be required).
A lumbar puncture on a neonate is performed under sterile conditions and the following equipment is required:
- clean trolley
- masks - for the person performing procedure and assistant
- sterile gown pack
- sterile gloves
- sterile plastic drape
- sterile scissors
- basic dressing pack
- antiseptic solution as per unit protocol
- ampoule of sterile water
- lumbar puncture needle - short bevel, styletted, 22 or 25 gauge
(LP needles with a stylet are used in order to avoid later formation of a dermoid cyst.
23 or 25g needles are occasionally used by experienced practitioners when a lumbar puncture cannot be satisfactorily achieved with a standard LP needle.)
- sterile pack of three CSF collection tubes
- blue underpad.
Equipment required for lumbar puncture
Preparation for lumbar puncture
- Inform the parents of the planned procedure for their infant whenever possible.
- Perform the procedure in a warmed, draught-free area with good access and light (preferably resuscitaire).
- Resuscitation equipment must be readily available and in working order.
- Ensure the infant has not been fed in previous hour (aspirate infant's stomach if fed within the past hour).
- Perform cardiorespiratory and oxygen saturation monitoring during procedure (and for one hour after procedure).
- Consider infant's need for pain relief. Options include:
- application of EMLA (0.5-1 g) to proposed site 60-90 minutes before the procedure
- use of oral sucrose
- subcutaneous infiltration of lignocaine
- intravenous bolus dose or infusion of morphine.
The spinal cord in neonates extends further down the spinal canal than in older children. Lumbar punctures should be performed at or below the L4 level. The L4 landmark is as in older children - the line of the top of the iliac crests.
Positioning of infant for lumbar puncture
Position the infant in the lateral position with trunk well flexed by the assistant holding the shoulders and legs forward but with the neck extended and legs at a 90 degree angle to the hips - at the edge of the cot. Ensure infant's back is parallel to the cot, with hips and shoulders vertical to the cot (not rotated).
Some degree of flexion of the spine is helpful since it opens up the interspinous spaces and also stretches the skin over the processes, allowing better definition of landmarks. It is not necessary to flex the neck with compromise of the airway and increase in cerebral venous pressure. Infants may not tolerate the procedure well. This is usually because of excessive flexion of the infant.
Alternatively, term infants may be placed in a seated position on the edge of the table, with trunk flexed forwards, stabilised from the front by the assistant. The infant's shoulders and hips are held in order to maintain vertical alignment of the hips and shoulders during the procedure. This has been shown to be the best tolerated and to also have the best chance of obtaining CSF.
Procedure for lumbar puncture
- Place infant on blue underpad (ensure underpad is removed after skin preparation if any pooling of skin preparation solution has occurred).
- Position baby. Identify landmarks. Ensure the baby is as straight as possible (particularly avoid rotation), but do not apply flexion to the trunk until the needle is about to be inserted.
- Apply face mask.
- Wash hands, gown and glove.
- Cut 3 cm diameter hole in middle of plastic drape. (Plastic drape helps visualization of infant during procedure.)
- Prepare the skin. Wait for prep to dry.
- Identify L4. It helps to keep two fingers of your left hand locating it - one each side.
- Enter skin strictly in midline, aiming slightly towards the head at between 70 and 90 degrees.
- Once through the skin, STOP. Wait for the infant to resettle.
- Reorient yourself, making sure that you are still in the midline and advancing at the appropriate angle. The subsequent advance of the needle is less distressing than the initial insertion.
- Advance needle about 0.5 cm. Remove stylette and observe for CSF flow. If negative, fully reinsert the stylette and advance a little further. Repeat this process until CSF is obtained.
- A ‘pop’ or ‘give’ may be felt as the needle passes through the posterior ligaments and dura, but do not rely on this. The ‘stop-start’ approach is less likely to give a bloody tap.
- Allow CSF to drip into at least two tubes. A minimum of 10 drops/tube is required for microbiological and biochemical examination.
- Measure CSF pressure using a manometer if you are doing a therapeutic tap. For a therapeutic tap, the maximum volume to be tapped is 2 per cent of body weight.
- When adequate CSF has been obtained, replace the stylet and then remove the needle. Apply pressure to the puncture site with a sterile cotton wool ball or gauze to control ooze. When ooze has ceased, use a band-aid or flexible collodion as dressing.
- Wipe excessive antiseptic prep from the skin with sterile water.
- Discard stylette and needle into sharps container.
No CSF obtained
- Consult a more experienced practitioner.
- Attempt procedure using the next higher intervertebral space.
- Failure to obtain CSF should not delay antibiotic treatment in a septic neonate cell counts and PCR obtained after antibiotics are still meaningful.
Blood-stained CSF obtained
- Possible traumatic bleeding - blood staining tends to clear as the CSF flows
- Possible subarachnoid space bleeding
- Specimen is still useful for culture, but repeat procedure may be required (usually 24-48 hours later)
- If subarachnoid bleeding is strongly suspected, proceed to cranial ultrasound or other imaging
Care of infant after the procedure
- In the absence of compelling evidence, it is advised that the infant remain horizontal for 60 minutes after the procedure to minimise the chance of headache.
- Offer dummy or consider use of paracetamol if infant is distressed following procedure.
- Discontinue cardiorespiratory and oxygen saturation monitoring one hour following procedure, unless ongoing monitoring is otherwise indicated.
- Continue oxygen saturation monitoring for four hours post procedure if sedation with narcotics was administered prior to procedure. Sedated infants should remain nil orally for two hours post procedure.
- Continue routine monitoring of infant, including checking the temperature after the procedure.
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First published: May 2014
Last reviewed: October 2018
Review by: December 2018