Lumbar Puncture

NEJM video guide

Indications

  • Diagnosis of suspected CNS infections, CNS malignancies, demyelinating diseases, IIH, NPH, autoimmune encephalitis, suspected SAH with negative imaging
  • Administration of medications intrathecally, including anesthetics and chemotherapy agents.

Absolute Contraindications

  • Increased intracranial pressure with risk of herniation (e.g. space-occupying lesions, cerebral edema, obstructive hydrocephalus), infection or epidural abscess over puncture site, trauma to lumbar vertebrae

Relative Contraindications

  • Elevated intracranial pressure, thrombocytopenia, bleeding diatheses, Coagulopathies, prior lumbar surgery

Consent

  • Common risks: back pain (~66%), severe headache
  • Rare risks: spinal hematoma (<0.001%), weakness, radicular pain/numbness, bleeding, brain function problems, CNS infection, brain herniation

Pre-procedural considerations

  • Bleeding risk guidelines: Plts > 50k, INR < 1.6 (stricter guidelines d/t spinal hematoma risk)
  • CT head not generally needed prior to LP to rule out mass lesion; consider if presence of focal neurologic signs, papilledema, recent seizure, or immunocompromise
  • Consider sending to fluoro-guided if: attempts without imaging are unsuccessful, obese pts with no palpable anatomy, severe scoliosis, prior spine surgery, borderline low plts and multiple sticks might be needed, or pt requires heavy sedation
  • Labs: cell count w/diff, BF culture, glucose, protein; freeze sample for future/additional labs (order in Epic); if infectious or neurological labs are needed, consider consult first
  • Ensure lateral decubitus position for opening pressure with glass pressure manometer

Supplies

  • Lumbar puncture kit
    • Skin prep
    • Drapes o 20- or 22-gauge needle for lidocaine administration
    • Collection tubes
    • Manometer
    • Spinal needle of 20 or 22 gauge
  • Sterile gloves
  • Hair covering, eye protection (especially if high OP anticipated or done with patient in sitting positing), and mask
  • Anesthetic use: Lidocaine 1-2% (likely need more than what is provided in kit
  • Table
  • Chlorhexidine x3 Always prepare 1 or 2 backup 20g LP needles (yellow cap)
    • in case of occlusion by superficial bleeding
    • the LP needle in the kit are too long, unwieldy
  • Consider sterile towels or even a Safe-T centesis kit because the drape in the LP kits have become increasingly poor quality (no adhesive, doesn’t stick to patient; just thin paper)

Procedural considerations

  • US Probe: linear (can use curvilinear in obese pts) in transverse axis to establish midline and in sagittal axis to identify spinous processes
  • Anesthetic use: lidocaine 1-2% (likely need more than what is provided in kit; consider empiric anesthetization of 2 spaces ± Pain-Ease spray
  • Higher rate of success if stylet is removed before entering subarachnoid space to better observe flow of CSF once in the subarachnoid space. Stylet should be replaced prior to LP needle removal
  • Ensure lateral decubitus position, if opening pressure (OP) via manometry is desired.
  • If OP is not necessary, sitting position greatly increases success.
  • Normal opening pressure ranges from 7 to 18cmH2O (manometer goes up to 35; it is not commonplace to use the plastic extender)
  • See video above for details on identifying correct target and procedural steps
  • A common occurrence is patient report of leg pain; this implies needle has travelled too laterally; consider redirecting needle towards midline in the contralateral direction to the affected leg (if tingling down R leg, go L)
  • Aspiration of CSF = increased risk of bleeding. Don’t aspirate!
  • Volume removal for studies: Basic only 2mL per tube in 1-4. Many studies ordered: 3mL per tube (*consider calling lab to confirm). Cytology desired: call lab to confirm amount needed (rule of thumb 2/2/6/2mL); Tube 4 is sent for micro to reduce contamination. Therapeutic high volume: 30mL max
  • Therapeutic high volume: 30mL max; therapeutic LP is typically done by consultants, with CSF removal until one of two end points are reached; either closing pressure <20 and/or 35ml of removal (neurology restricts to 50ml)

Post-procedural considerations

  • Post-LP headache (~10%): encourage pt to lay flat to reduce the intensity of symptoms (but does not prevent it); if prolonged, consider blood patch (consult Anesthesia)
  • Neuro changes OR bleeding complications: STAT non-contrast MRI lumbar spine for epidural hematoma, consult Neurosurgery, q1 neuro-checks x4hrs then q2 for 24-48hr
  • Resuming anticoagulation: 1h UFH, 4h LMWH, 6-8h rivaroxaban/apixaban, 6h dabigatran/fondaparinux. Longer periods should be considered after traumatic tap, and post-procedure monitoring of neurological function is recommended for all pts
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