Lumbar Puncture¶
Indications¶
- Diagnosis of suspected CNS infections, CNS malignancies, demyelinating diseases, IIH, NPH, autoimmune encephalitis, suspected SAH with negative imaging
Absolute Contraindications¶
- Increased intracranial pressure with risk of herniation (i.e. space-occupying lesions, cerebral edema, obstructive hydrocephalus), infection or epidural abscess over puncture site, trauma to lumbar vertebrae
Relative Contraindications¶
- ↑ intracranial pressure, thrombocytopenia, bleeding diatheses
Consent¶
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Common risks: back pain (~66%), severe headache
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Rare risks: spinal hematoma (\<0.001%), weakness, radicular pain/numbness, bleeding, brain function problems, CNS infection, brain herniation
Pre-procedural considerations:¶
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Bleeding risk guidelines: Plts > 50k, INR \< 1.6 (stricter guidelines d/t spinal hematoma risk)
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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
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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
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Anticoagulation: full dose LMWH must be off 24h, ppx LMWH off 12h, ppx heparin off 8h, hep gtt off 4-8hrs with repeat lab demonstrating normalized PT, P2Y12 inhibitors should be off 7 days to avoid bleeding risks, IR guidelines require Plavix to be off 5 days (ASA alone is OK)
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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
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Ensure lateral decubitus position for opening pressure with glass pressure manometer
Procedural considerations¶
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US Probe: Linear (can use curvilinear in obese pts) in transverse axis to establish midline & in sagittal axis to identify spinous processes
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Anesthetic use: Lidocaine 1-2% (likely need more than what is provided in kit; consider empiric anesthetization of 2 spaces ± Pain-Ease spray
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Increased number of attempts = increased success rates
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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
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Aspiration of CSF = increased risk of bleeding. Don’t aspirate!
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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
Post-procedural considerations¶
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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 (c/s Anesthesia)
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Neuro changes OR bleeding complications: STAT non-contrast MRI lumbar spine for epidural hematoma, q1 neuro-checks x4hrs then q2 for 24-48hrs & consult NSGY
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Sample cannot be tubed; someone must walk fluid to the lab
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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