Lumbar Puncture

Last Updated on by FRCEM Intermediate

Indications

  • CNS infection (e.g. bacterial, viral, TB meningitis)
  • subarachnoid hemorrhage (12 hours after onset of headache if the CT is negative)
  • neurological disease (e.g. multiple sclerosis, Guillain–Barré syndrome).
  • removal of CSF (e.g. idiopathic intracranial hypertension)
  • spinal anaesthesia for lower limb/lower abdominal surgery.

Contraindications

Absolute

  • Patient refusal
  • GCS 8 or less or deteriorating
  • Focal neurological signs or abnormal posture
  • Clotting abnormality- Risk of epidural hematoma causing cord compression
    • Patient on full anticoagulation:
      • warfarin – stop and ensure INR <1.5 unfractionated
      • heparin infusion – stop infusion and ensure APTT normal (after approx 4 h)
    • Prophylactic anticoagulation:
      • unfractionated heparin – wait 4 h after dose, can give heparin 1 h after LP
      • low molecular weight heparin – wait 12 hours after dose, can give 4 hours after LP
    • Platelets – ensure >80 × 103
    • Aspirin/NSAIDs – no increased risk of spinal/epidural haematoma
  • Raised intracranial pressure – If raised ICP is suspected then a CT scan should be performed before LP to look for hydrocephalus or a space-occupying lesion.
  • Local infection at the injection site – Risks causing epidural abscess or meningitis

Relative

  • Systemic sepsis. Risks causing epidural abscess or meningitis
  • Neurological disease.- Any subsequent new neurological symptoms can be blamed on the LP. The indication needs to be strong, the patient’s informed consent given and a full neurological examination should be performed and documented before LP.

Indications for performing brain CT scanning before lumbar puncture 

  • Altered mental Status
  • Focal neurologic signs
  • Papilloedema
  • Seizure within the previous week
  • Patients who are immunocompromised
  • Patients who are older than 60 years
  • Patients with known CNS lesions

Anatomy

  • In adults the spinal cord ends at the lower border of L1 (L3 in children), and so insertion of the needle must be below this level to avoid possible spinal cord injury.
  • The CSF is located within this subarachnoid space.
  • Layer Lumbar puncture: “SSS I LED AS”
    • Skin
    • Superficial fascia
    • Supraspinous ligament
    • Interspinous ligament
    • Ligamentum flavum
    • Epidural space
    • Dura mater
    • Arachnoid
    • Subarachnoid space containing cerebrospinal fluid

Landmark

  • The posterior iliac crests are easily palpated in most patients. A line drawn between the superior border of the posterior iliac crests will intersect the L4 spinous process- Tuffier’s line (L3–L4 level)
  • Using this surface landmark, the L3-L4-L5 interspaces can be localized.
  • Identify the L3-L4 interspinous process space midline as the needle insertion site.
  • If insertion at this space is unsuccessful, try the L4-L5 space
  • To avoid damaging the spinal cord, do not go above the spinal cord L2- L3 space.
  • Lumbar puncture can be performed with the patient sitting or lying in a lateral position. The sitting position allows easier identification of the midline

Samples

  • Collect 5–10 drops (approx 1 mL) of CSF into three sequentially numbered universal containers and also into a fluoride tube (grey top) for glucose measurement
  • For suspected meningitis : send for urgent microscopy, culture, protein, and glucose
  • Other possible tests: cytology, virology, TB culture, syphilis serology, oligoclonal bands and xanthochromia  -( for Suspected subarachnoid hemorrhage – 12 hours after onset of headache if the CT is negative)

Complications

  • Back pain – Localised soft tissue trauma at the injection site is common and may last a few days.
  • Postdural puncture headache – Risk is minimised by using atraumatic needles (Whitacre, Sprotte) of small gauge, but CSF collection can take a long time if needles smaller than 22G are used. There is no evidence that the amount of CSF taken or lying fl at after LP reduces the risk. All cases will resolve with time but if symptoms are severe, liaise with an anaesthetist to consider an epidural blood patch. For this 20 mL of the patient’s blood is taken from a vein under aseptic conditions and injected into the epidural space at the level of the LP. This blood will clot and plug the hole preventing further CSF leak.
  • Neurological sequelae – Temporary symptoms of paraesthesia or motor weakness may result from needle damage or stretching of a nerve root.
  • Infection – Meningitis, encephalitis or epidural abscess are very rare but can result if strict aseptic technique is not followed.
  • Hematoma – A spinal subdural or epidural hematoma can cause spinal cord compression
  • Cerebellar tonsillar herniation (coning)- In the presence of increased ICP the cerebellar tonsils may be forced through the foramen magnum, resulting in compression of the medulla and neurological
    deterioration or death.

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