Lumbar Puncture

Aka: Lumbar Puncture, Spinal Tap

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II. Indications

  1. Suspected CNS Infection
    1. Meningitis
    2. Encephalitis
  2. Evaluate for Hemorrhagic CVA (Subarachnoid Hemorrhage)
    1. Hemorrhage suspected despite negative Head CT
    2. Head CT not available
  3. Diagnostic Chemistry Evaluation
    1. CSF Gamma Globulin (Multiple Sclerosis)
  4. CSF Dynamics
    1. Spinal block diagnosis (Queckenstedt test)
    2. Normal Pressure Hydrocephalus evaluation
      1. Katzman infusion
      2. Radionucleotide cisternography
  5. CSF Cytology
    1. Carcinomatous Meningitis
    2. Lymphomatous Meningitis
  6. Therapeutic Lumbar Puncture
    1. Methotrexate infusion (CNS Leukemia)
    2. Amphotericin B infusion (fungal Meningitis)
    3. Removal of fluid to decrease Intracranial Pressure
      1. Pseudotumor Cerebri
      2. Headache associated with Subarachnoid Hemorrhage

III. Contraindications

  1. Local infection at Lumbar Puncture site
  2. Cerebral mass lesion (risk of Herniation)
    1. Large Brain Abscess
    2. Brain Tumor (especially posterior fossa)
    3. Subdural Hematoma
    4. Intracranial Hemorrhage
  3. Papilledema
  4. Uncorrected Bleeding Disorder
    1. Coagulopathy secondary to Cirrhosis or Alcoholism
    2. Anticoagulation
    3. International Normalized Ratio (INR) >1.5
    4. Severe Thrombocytopenia (Platelet Count <50,000)
    5. Clopidogrel (or other Platelet ADP Receptor Antagonist)
      1. Aspirin alone is not a contraindication to LP

IV. Precautions

  1. Obtain CT Head before Lumbar Puncture if significant risk factors for CNS mass
    1. Do not delay empiric Antibiotics for CT Head if Bacterial Meningitis suspected
    2. DO obtain Blood Cultures before Antibiotics
  2. Indications for CT Head before Lumbar Puncture
    1. CSF Shunt
    2. Hydrocephalus
    3. Trauma
    4. Known Intracranial Mass
    5. Recent neurosurgery
    6. Papilledema
    7. Focal neurologic deficit
    8. New onset Seizures within the last week
    9. Significantly Altered Level of Consciousness
    10. Immunocompromised (HIV, Immunosuppressant medication use, transplant patient, Chemotherapy)
  3. Increased Intracranial Pressure
    1. Monitor CSF Pressure with inline manometer while withdrawing CSF
    2. Do not drop CSF Pressure more than 50% of opening pressure with Lumbar Puncture

V. Equipment: Needle types

  1. Needle Lengths
    1. Typical body habitus: 3.5 inch needles are adequate
    2. Large patients: 6 inch needles may be needed
  2. Standard spinal needle (Quincke Needle, 20 g)
    1. Easier to obtain successful Spinal Tap
    2. Higher Incidence of post-dural Headache (22% in one study)
  3. Atraumatic or blunt spinal needle (Sprotte needle, Whitaker needle) - preferred
    1. Smaller tapered needle with blunt tip (typically 20-22 g)
    2. Requires first puncturing the skin with a larger bore needle (18 g) deep enough to draw a small amout of blood
    3. Then pass the blunt tipped needle through the created hole
    4. Significantly lower Spinal HeadacheIncidence (9% compared with 22% with cutting needle)
      1. Castrillo (2015) Spine J 15(7): 1572-6 +PMID: 25794941 [PubMed]
    5. Flow rates via blunt tipped needles are at least as fast as cutting needles
      1. Pelzer (2014) Neurol Sci 35(12): 1997-9 +PMID: 25139108 [PubMed]
  4. References
    1. Orman and Reed in Herbert (2017) EM:Rap 17(4): 7
    2. Thomas (2000) BMJ 321:986-90 [PubMed]

VI. Technique: Adults

  1. Anxiolysis
    1. Consider Midazolam 2 mg IV before procedure
  2. Patient positioning
    1. Lateral decubitus position (required if performing opening pressure)
      1. Fetal Position
      2. Back at right angles to bed
    2. Sitting position
      1. Leaning forward, holding a pillow
  3. Location (most important factor in successful LP)
    1. Mark midline spinous process between iliac crests
    2. Corresponds with L3-L4 or L4-L5 interspace
    3. Consider Ultrasound (high frequency linear probe)
      1. Identifies midline (spinous processes if not palpable)
      2. Identifies interspaces
      3. Estimates insertion depth
  4. Anesthesia
    1. Consider 10 cc syringe Lidocaine 2% with Epinephrine (not in LP kit)
    2. Infiltrate planned LP track with 4 cc and a Field Block around the track with another 4-5 cc
  5. Spinal needle insertion
    1. Use 20 to 22 gauge spinal needle
    2. Insert needle bevel parallel to long axis of spine (faces laterally)
    3. Keep needle parallel with bed
    4. Angle needle toward Umbilicus
    5. Insert needle until pop is felt or CSF fluid flows
      1. Walk the needle in slowly in steps (checking for CSF flow with each step)
      2. Coughing or Valsalva Maneuver increases flow
  6. Mis-directed Needle hits bone
    1. Withdraw needle to skin level and redirect (angling slightly up or slightly down)
    2. Confirm midline and at an interspace
  7. Adjuncts to difficult Lumbar Puncture
    1. Fluoroscopy
    2. Paramedian approach
      1. Indicated in older patients with calcified spinous ligaments
      2. Insertion is shifted 1 cm, horizontally off midline
        1. Angle needle insertion toward midline

VII. Technique: Infants

  1. Spinal needle: 22 gauge 1.5 inch
  2. Location
    1. Stay below L3
  3. Positioning
    1. Infant sitting, with helper holding arms and legs
      1. Consider having a second assistant or parent stabilize head or neck
    2. Alternatively, lateral decubitus position may offer better immobilization of infant
    3. Avoid excessive neck flexion (head in relatively neutral position)
      1. Neck flexion risks airway closure and apnea
  4. Additional pearls
    1. Depth is superficial in an infant
    2. Consider topical or Local Anesthetic
      1. LMX4 applied 30 minutes before procedure OR
      2. EMLA applied 60 minutes before procedure OR
      3. Lidocaine 1% with Epinephrine, raising a small subcutaneous wheal over the landmark
    3. Consider sedation
      1. Oral 30% Glucose solution (newborns up to age 6 weeks) OR
      2. Intranasal Fentanyl
    4. May remove stylet after entering skin
      1. Before entering skin, Epidermis may plug needle
      2. However, after skin entry, stylet removal makes it less likely to miss the space
    5. May allow for 1 additional CSF WBC for every 1000 CSF RBCs
      1. Lyons (2017) Ann Emerg Med 69(5): 622-31 [PubMed]
    6. Risk factors for failed Lumbar Puncture in infants
      1. Age <3 months
      2. Spinous processes not visible or palpable
      3. Patient movement
      4. Inexperienced provider
      5. Nigrovic (2007) Ann Emerg Med 49(6): 762-71 +PMID: 17321005 [PubMed]

VIII. Standard CSF Orders

  1. Tube 1
    1. Gram Stain
    2. Culture and sensitivity
  2. Tube 2
    1. CSF Glucose
    2. CSF Protein
  3. Tube 3
    1. CSF Cell Count with Differential
  4. Tube 4
    1. CSF Latex Agglutination (Antigens)

IX. Complications

  1. Spinal Headache
  2. Unexpected rise in Intracranial Pressure
  3. Worsening of spinal block
  4. Spinal Epidural Hematoma
  5. Iatrogenic Meningitis (rare)
    1. Pandian (2004) J Hosp Infect 56(2):119-24 +PMID: 15019223 [PubMed]

X. References

  1. Claudius and Behar in Herbert (2017) EM:Rap 17(11): 5
  2. Weingart and Swaminathan (2024) EM:Rap Critical Care Malebag: I Love Doing LPs, accessed 3/3/2024
  3. Mount (2017) Am Fam Physician 96(5): 314-22 [PubMed]

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