Lumbar Puncture Procedure

Summary

it is recommended that Lumbar Puncture needles are used in order to avoid later formation of dermoid cyst

Indications

sampling of cerebrospinal fluid (CSF) for microscopy, evidence of bacterial, viral or fungal infection and biochemical measurement of protein and sugar levels, or markers of metabolic disorder
therapeutic tap to limit ventricular dilatation in post haemorrhagic hydrocephalus (serial taps may be required)

Equipment

  Clean trolley
  Masks - for 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 3 CSF collection tubes
  Blue underpad

Preparation

when possible, parents are informed of planned procedure for their infant
resuscitation equipment is readily available and in working order
area is draught free
ensure 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 1 hour after procedure)
- consider infant's need for pain relief including
- application of EMLA (0.5 -1g) to proposed site 60-90 minutes before procedure
- use of oral sucrose (link to section)
- subcutaneous infiltration of lignocaine
- intravenous infusion of morphine

Anatomical Landmarks

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

Infants may not tolerate the procedure well. This is usually because of excessive flexion of the infant. 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.

Position infant in the lateral position with trunk well flexed by the assistant holding the shoulders and legs forward, but with neck extended and legs at 90 degrees 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.

Alternatively, term infants may be placed in a seated position on the edge of the table, with trunk flexed forward, 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

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 baby is as straight as possible.
apply face mask
wash hands, gown and glove
cut hole in middle of plastic drape. (Plastic drape helps visualization of infant during procedure)
prepare 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 at between 70 and 90 deg, slightly headwards.
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, reinsert stylette and advance a little further. Repeat this 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.
for a therapeutic tap, the volume limit is 2% of body weight. If doing a therapeutic tap, CSF pressure should be measured using a manometer.
remove needle. Press site to control ooze with sterile cotton wool ball. After ooze has ceased use band-aid or flexible collodion as dressing.
if required - clean antiseptic solution from skin with Sterile Water
discard stylet and needle into sharps container.

Procedure Failure

No CSF
- Consult a more experienced practitioner
- Attempt procedure using the next higher intervertebral space
Blood stained CSF
- Possible traumatic bleeding - blood staining tends to clear
- Possible subarachnoid space bleeding

Care of Infant Following Procedure

continue routine monitoring of infant
check temperature after procedure
discontinue cardiorespiratory and oxygen saturation monitoring (if not otherwise indicated) 1 hour following procedure
if sedation with narcotics was administered prior to procedure, continue oxygen saturation monitoring for 4 hours post procedure. Sedated infants should remain nil orally for 2 hours post procedure
a infants are lying down after the procedure, distress due to headache should not occur. However if infant is distressed following procedure offer dummy or consider use of paracetamol
in the absence of compelling evidence it is advised that the infant remain horizontal for 60 minutes after the procedure

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