Indications
- • Suspected meningitis/encephalitis
- • Subarachnoid haemorrhage (CT-negative)
- • Idiopathic intracranial hypertension
- • CNS demyelination workup
Contraindications
- ⚠ Raised ICP / focal signs / GCS ≤12 without prior CT
- ⚠ Coagulopathy (INR >1.4, platelets <50)
- ⚠ Local infection over site
- ⚠ Spinal cord lesion above puncture
Equipment
- • Sterile pack, gown, gloves
- • Chlorhexidine, drapes
- • 1% lidocaine, 5/10 mL syringes
- • Spinal needle (22G atraumatic preferred)
- • 3-way tap + manometer
- • 3–4 numbered universal containers + fluoride tube for glucose
Technique
- • Position: lateral decubitus knees-to-chest, or sitting forward
- • Identify L3/4 or L4/5 — line between iliac crests = L4
- • Clean, drape, infiltrate skin + interspinous ligament with lidocaine
- • Insert spinal needle in midline, bevel parallel to fibres, aim towards umbilicus
- • Advance until 'give' on entering dura → withdraw stylet → CSF flow
- • Measure opening pressure (legs straightened)
- • Collect 10–20 drops per tube × 3–4 + glucose tube
- • Replace stylet before withdrawing needle
Complications
- ⚠ Post-LP headache (epidural blood patch if severe)
- ⚠ Bleeding / spinal haematoma
- ⚠ Infection (meningitis, discitis)
- ⚠ Cerebral herniation (if raised ICP)
- ⚠ Nerve root irritation
Aftercare
- • Lie flat 1 h, encourage fluids
- • Document opening pressure, appearance, samples sent
- • Send CSF: cell count, protein, glucose (paired serum), culture, lactate, viral PCR, xanthochromia ≥12 h post-onset if SAH
Clinical pearls
- • Atraumatic needles halve post-LP headache rates
- • Send xanthochromia in dark tube; spectrophotometry at 12 h
- • If dry tap, reposition or try one space up
Perform under supervision until competent. Follow local SOPs and consent policy.
