What are the procedure, criteria, and complications for a lumbar puncture (LP)?

Lumbar Puncture: Procedure, Criteria, and Complications

Atraumatic (pencil-point) needles should be used for all lumbar punctures as they significantly reduce the risk of post-dural puncture headache and other complications while maintaining procedural success rates. 1

Procedure for Lumbar Puncture

Patient Positioning

• Position patient in lateral decubitus position with knees drawn to chest and chin tucked (fetal position)
• Alternative: seated position with patient leaning forward over a support

Equipment Required

• LP tray with sterile drapes and gloves
• Antiseptic solution (chlorhexidine or povidone-iodine)
• Local anesthetic (1% lidocaine)
• Spinal needles (preferably atraumatic/pencil-point needles)
• Manometer for pressure measurement
• Collection tubes for CSF samples 2

Technique

1. Identify the correct interspace: Locate L3-L4 or L4-L5 interspace (below the termination of the spinal cord) using the iliac crest as a landmark
2. Prepare the site: Clean with antiseptic solution and drape
3. Administer local anesthetic: Infiltrate skin and deeper tissues with lidocaine
4. Insert the needle:
   • Use atraumatic (pencil-point) needle (22G or larger) with bevel parallel to the longitudinal dural fibers
   • Advance slowly until a "pop" is felt when penetrating the dura
   • Remove stylet to check for CSF flow 1, 2
5. Measure opening pressure: Connect manometer and record pressure with patient relaxed
6. Collect CSF samples: Typically 4 tubes (5-20 mL total) for analysis
7. Replace stylet before withdrawal: This reduces the risk of post-LP headache
8. Apply sterile dressing to puncture site 2, 3

Criteria for Lumbar Puncture

Indications

1. Diagnostic:

   • Suspected CNS infections (meningitis, encephalitis)
   • Suspected subarachnoid hemorrhage with negative CT
   • Inflammatory neurological disorders (multiple sclerosis, Guillain-Barré)
   • Neoplastic diseases affecting CNS
   • Suspected idiopathic intracranial hypertension 4, 5

2. Therapeutic:

   • CSF removal to reduce intracranial pressure
   • Administration of intrathecal medications
   • Management of cryptococcal meningitis with daily LPs 2

Contraindications

1. Absolute:

   • Increased intracranial pressure with evidence of mass lesion
   • Infection at the puncture site
   • Severe cardiorespiratory compromise
   • Uncorrected coagulopathy 2, 5

2. Relative (neuroimaging recommended before LP):

   • Focal neurological signs
   • Papilledema
   • Altered mental status (GCS ≤12)
   • Immunocompromised state with focal neurological findings
   • History of CNS disease
   • Recent seizure 2

Laboratory Parameters

• Ensure normal coagulation parameters (INR <1.5)
• Platelet count ≥100 × 10⁹/L
• Consider timing if patient is on anticoagulants 2

Complications of Lumbar Puncture

Common Complications

1. Post-dural puncture headache (PDPH):

   • Incidence: Up to 35% with conventional needles, significantly reduced with atraumatic needles
   • Characteristics: Positional headache worsening when upright
   • Prevention: Use atraumatic needles, smaller gauge needles, replace stylet before withdrawal
   • Management: Hydration, caffeine, analgesics; severe cases may require epidural blood patch 1, 2, 6

2. Back pain:

   • Usually mild and self-limiting
   • Due to local tissue trauma 1, 6

Serious Complications (Rare)

1. Cerebral herniation:

   • Risk increased with space-occupying lesions
   • Can be fatal
   • Avoid LP if increased ICP with mass effect is suspected 7, 6

2. Infection:

   • Meningitis, epidural abscess
   • Extremely rare with proper aseptic technique 7

3. Bleeding:

   • Epidural or subdural hematoma
   • Higher risk in coagulopathies 6

4. Nerve root irritation:

   • Transient radicular pain or paresthesias
   • Usually resolves spontaneously 6

5. Pneumocephalus/pneumorrachis:

   • Extremely rare complication
   • Can be fatal in cases with underlying anatomical abnormalities 7

Special Considerations

CSF Analysis

Normal CSF parameters:

• Opening pressure: 10-20 cmH₂O
• Appearance: Clear, colorless
• WBC count: <5 cells/μL
• Glucose: >45 mg/dL (or CSF:plasma ratio >0.6)
• Protein: <45 mg/dL
• Culture: Negative 2

Post-Procedure Care

• Bed rest is not proven to prevent PDPH but may be recommended for 1-2 hours
• Encourage fluid intake
• Provide analgesia as needed
• Instruct patient about symptoms requiring medical attention (severe headache, fever, neurological changes) 2, 3

Quality Improvement Tips

• Use atraumatic needles as standard practice
• Ensure proper training for all practitioners performing LP
• Develop institutional protocols for LP procedure and post-procedure care 1, 3