Lumbar puncture

Summary

Definition: needle puncture of the spinal canal below the level of termination of the spinal cord (usually at L4–L5). Cerebrospinal fluid is sampled and pressure measured.

Indications

1. ▪ Suspected subarachnoid haemorrhage (SAH) following CT scan.

2. ▪ Suspected CNS infections.

3. ▪ Therapeutic reduction of raised ICP (done following a CT scan only in experienced neurosurgical hands due to risk of brain herniation).

4. ▪ CSF sampling for other conditions.

Contraindications

1. ▪ Local skin infections over puncture site.

2. ▪ Evidence of raised ICP on clinical exam (papilloedema) or on CT.

3. ▪ Suspected spinal cord mass or intra-cranial mass lesion.

4. ▪ Bleeding disturbance or warfarin therapy with INR >1.4.

5. ▪ Spinal column deformities (may require fluoroscopic assistance).

Prepare the patient

1. ▪ Explain procedure to the patient.

2. ▪ Prepare lumbar puncture (LP) tray as follows:

3. ▪ Spinal needle (Quinke type) 20G for children, 22G for adults.

4. ▪ Antiseptic solution.

5. ▪ Sterile drapes, gloves and gown.

6. ▪ Disposable manometer.

7. ▪ Three-way valve.

8. ▪ Intravenous line connector and tube.

9. ▪ Local anaesthetic – 5 ml of 1% lidocaine.

10. ▪ One fluoride and three plain CSF collection bottles.

11. ▪ Expose the patient and place on their left side with their back perpendicular to the edge of the bed. Ask the patient to flex their knees and bring their chin down (the fetal position) which helps to widen the intervertebral spaces (see Figure 128).

12. ▪ Palpate both iliac crests. A line in this plate goes through the L4 vertebra in the midline. Either the L4/L5 or L3/4 intervertebral space can be used for LP, and should be marked with a permanent marker (see Figure 128).

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