Paediatrics: Lumbar puncture

Lumbar puncture

Indications 

To obtain sample of CSF for microbiological, biochemi-cal, or metabolic analysis; therapeutically drain CSF in communicating hydrocephalus.

Contraindications 

Include thrombocytopenia or coagulation defect, raised intracranial pressure, and significant cardiorespiratory compromise, as positioning may risk cardiorespiratory arrest.

Site 

L3–L4 intervertebral space (spinal cord may be as low as L2 in neonates).

Equipment

•   24–22G 1.5 inch spinal needle.

•   Antiseptic solution, e.g. 0.5% chlorhexidine.

•   Sterile dressing pack (including gauze, gloves, drapes).

•   Sterile sample containers; usually 3 are needed for M,C&S, protein, and glucose, but sometimes also for virology, cytology, or immunology.

•   Adhesive plaster or aerosol plastic dressing spray.

•   Pressure manometer and 3-way tap if measuring CSF opening pressure.

Procedure

•   Apply topical local anaesthetic cream to site under an occlusive dressing for 45min before the procedure.

•   Place child on their side with back along an edge of a firm surface.

•   Ask an experienced assistant to firmly, but gently, hold child with the spine maximally flexed. Beware compromising respiration!

•   Locate site. L4 spinous process lies on a line joining the iliac crests.

•   Using strict aseptic technique, clean the site with antiseptic solution and then create a sterile field by surrounding it with sterile drapes.

•   Inject local anaesthetic into site if child is  6mths old.

•   Insert spinal needle into intervertebral space slowly at 90° to the skin and aim in the direction of the umbilicus, i.e. slightly cephalad.

•   Advance needle slowly until there is a sudden give, which occurs as the dura is penetrated.

•   Remove stylet; wait for CSF to drain. If no CSF drains, advance needle very slowly and withdraw stylet every 1–2mm to check for drainage. If bone is struck or needle is fully inserted and no CSF obtained, remove the stylet and then withdraw cannula very slowly in case CSF appears.

•   Allow 10 drops of CSF to drain into each sample bottle.

•   If measuring CSF pressure, connect 3-way tap before collecting samples and direct fluid up attached manometer. Once opening pressure is measured, turn 3-way tap to allow CSF to drain.

•   If therapeutic CSF drainage is required, drain required amount.

•   Once drainage is complete, remove the needle and rub the puncture site with a sterile gauze swab while applying pressure.

•   Cover site with an adhesive plaster or aerosol plastic dressing.

•   The child should lie flat for the next 6hr and have hourly neurological observations and BP measurement.