What are the steps of a Lumbar Puncture (LP)?

Steps of a Lumbar Puncture (LP)

A lumbar puncture should be performed using an atraumatic narrow-bore needle (≥22-gauge) with the patient in lateral recumbent position, limiting attempts to 4 or fewer, and using passive CSF withdrawal to minimize complications. 1

Pre-Procedure Assessment

• Evaluate for contraindications:

  • Signs of increased intracranial pressure (papilledema, focal neurological signs)
  • Infection at the LP site
  • Coagulation abnormalities (INR >1.5, platelets <40 × 10⁹/L)
  • Respiratory or cardiac compromise
  • Continuous or uncontrolled seizures
  • Severely impaired consciousness (GCS ≤12) 1

• Consider neuroimaging before LP if any contraindications are present

Equipment Preparation

• Sterile gloves, mask, and cap
• Sterile drapes
• Antiseptic solution (chlorhexidine or povidone-iodine)
• Local anesthetic (1-2% lidocaine)
• Atraumatic (pencil-point) spinal needle, preferably 22-24 gauge 1
• Collection tubes (3-4 sterile tubes)
• Manometer for measuring opening pressure
• Dressing materials

Patient Positioning

• Position the patient either:
  • Lateral recumbent position (preferred): patient lies on side with knees drawn to chest, back at edge of bed 2
  • Sitting position: patient sits with back arched, feet supported, arms resting on table 2

Procedure Steps

1. Identify the puncture site:

   • Locate the L3-L4 or L4-L5 interspace (below the level of the spinal cord)
   • Use the iliac crests as landmarks (line connecting the top of the iliac crests crosses the L4 spinous process) 1

2. Prepare the site:

   • Clean the area with antiseptic solution in a circular motion from center outward
   • Apply sterile drapes around the area

3. Administer local anesthetic:

   • Infiltrate the skin and deeper tissues with 1-2% lidocaine
   • Allow 1-2 minutes for the anesthetic to take effect

4. Insert the needle:

   • Orient the needle bevel in the transverse plane (parallel to the dural fibers) 1
   • Insert the needle in the midline, aimed slightly toward the umbilicus
   • Advance slowly, feeling for the characteristic "pop" as the needle passes through the ligamentum flavum and dura

5. Remove the stylet:

   • Once in the subarachnoid space, remove the stylet to check for CSF flow
   • If no CSF appears, rotate the needle slightly or reinsert the stylet and advance slightly

6. Measure opening pressure 1:

   • Attach the manometer to the needle hub
   • Record the height of the CSF column (normal: <20 cm H₂O)

7. Collect CSF samples:

   • Collect 1-2 mL in each of 3-4 tubes for analysis
   • Label tubes sequentially (for "three tube test" if traumatic tap is suspected) 1
   • Up to 22 mL can be safely removed 1

8. Complete the procedure:

   • Replace the stylet before withdrawing the needle 1
   • Withdraw the needle in a single smooth motion
   • Apply pressure to the site with sterile gauze
   • Apply a sterile adhesive bandage

Post-Procedure Care

• Monitor for complications, particularly headache
• Post-LP headache is not prevented by bed rest, hydration, or reduced CSF volume 1
• Treatment for headache includes hydration, caffeine, and analgesics
• For severe headaches, an epidural blood patch may be necessary 1

Common Pitfalls and How to Avoid Them

• Multiple attempts: Limit to 4 or fewer attempts to reduce risk of complications 2
• Traumatic tap: Use atraumatic needles and proper technique to minimize bleeding 1
• Needle insertion too lateral: Stay in the midline to avoid nerve root irritation
• Inadequate CSF collection: Collect sufficient volume for all required tests 1
• Failure to replace stylet: Always replace the stylet before withdrawing to reduce CSF leakage 1
• Delaying antibiotics: Never delay antimicrobial therapy in suspected meningitis while awaiting CSF collection 1

Emerging Techniques

• Ultrasound guidance can help identify the appropriate interspace, especially in difficult cases 2
• Fluoroscopic guidance may be useful for patients with anatomical challenges (obesity, spinal deformities) 2

By following these steps and recommendations, the risk of complications from lumbar puncture can be minimized while ensuring adequate CSF collection for diagnostic purposes.