How to Perform Lumbar Puncture

• Indications:
  • Cerebrospinal fluid (CSF) evaluation
    • Meningitis
    • Subarachnoid hemorrhage
    • Neoplastic disease
  • CSF drainage
    • Communicating hydrocephalus
    • Pseudotumor cerebri
    • CSF leak
  • Intracranial pressure measurement
    • Communicating hydrocephalus
    • Pseudotumor cerebri
  • Intrathecal drug administration
    • Radiopaque contrast
    • Antibiotics
    • Antineoplastic chemotherapy
• Contraindications:
  All patients should receive intracranial imaging (computed tomography [CT] or magnetic resonance [MR]) to rule out an intracranial mass lesion prior to lumbar puncture.
  • Noncommunicating hydrocephalus
  • Intracranial mass (tumor, abscess, hematoma)
  • Coagulopathy or platelets <50K
  • Cellulitis at intended puncture site
  • Complete spinal block above tap site
  • Tethered cord syndrome
• Anesthesia:
  Lidocaine (0.5%, 1.0%, or 2.0%)
• Equipment:
  • Sterile prep solution
  • Sterile gloves and towels
  • 22-gauge and 25-gauge needles
  • 22-gauge, 20-gauge, or 18-gauge spinal needle with stylet
  • CSF collection vials
  • Manometer with stopcock
• Positioning:
  • Lateral: Patient is placed on his or her side with chin and knees tucked into the chest. This position is favored for accurate measurement of intracranial pressure.
    
  • Sitting: Patient sits on the side of a bed, flexed forward over a pillow for support. Intracranial pressure cannot be measured in this position. This position is superior for obese patients.
    
  
  
  Technique:
• Apply sterile prep solution to the lower back and cover region with sterile drapes.
• Identify the target interspace. The L4-5 interspace falls in the midline along the intercristal line connecting the superior iliac crests. Lumbar puncture may be attempted at the L3-4, L4-5, and L5-S1 interspaces.
• Inject 1 ml of lidocaine subcutaneously into the target interspace to raise a skin wheal. Anesthetize the deep tissues by injecting 3 ml of lidocaine through the skin wheal with a 22-gauge needle. Follow the intended track of the lumbar puncture needle, directed slightly cranially and parallel to the midline.
• Advance the needle deeper, aiming rostrally about 15°, taking care to maintain a midline trajectory. The needle will encounter slight resistance, then a pop will be felt, representing penetration through the ligamentum flavum (yellow ligament) into the thecal sac (the stylet should always be used with needle to prevent introduction of epidermal cells or subcutaneous tissue into thecal sac).
  
• If bone is encountered, pull the needle back to the subcutaneous tissues. The tip of the needle must be above the dorsal lumbar fascia to successfully redirect. Confirm that the trajectory is in the midline and that the patient is adequately flexed to open the interspace. If bone is encountered a second time, use the needle to “march” cranially to caudally until the thecal sac is entered. If this technique is unsuccessful, try another interspace or reposition the patient for the sitting approach.
• Once the needle is in the thecal sac, remove the stylet and observe for CSF. If blood appears, allow blood to drain and observe for clearance. If blood clears, then the tap was traumatic. If blood does not clear and blood clots, replace stylet, withdraw needle, and reattempt. If blood does not clear and does not clot, the patient may have had a subarachnoid hemorrhage and samples should be sent to the laboratory for cell counts and examined for xanthochromia.
• Once CSF flow is established, place stopcock on end of spinal needle with manometer. Rotate spinal needle so that bevel is pointed cranially. Open stopcock and measure CSF pressure in cm H2O (Normal <15 cm H₂O; borderline 15–20 cm H₂O; abnormal >20 cm H₂O).
• Collect CSF samples in tubes. The following tubes should be sent for analysis on every lumbar puncture performed:
• • • Cell count
    • Protein and glucose
    • Culture and sensitivity
    • Cell count (to compare with first cell count)
  • Replace stylet and withdraw needle.
  • Place sterile gauze over puncture site. Changes in mental status, vital signs, and pupil size and reactivity must be carefully monitored.
• Complications and Management:
  • Tonsillar herniation
    • Manifests initially as altered mental status, followed by cranial nerve abnormalities (third nerve palsy, respiratory difficulties) and Cushing response (hypertension, bradycardia, respiratory depression). May be rapidly fatal.
    • Immediately remove needle and raise the head of bed to improve venous return from the brain.
    • Administer 1 g/kg of mannitol intravenously.
    • Intubate patient and hyperventilate to a goal PCO₂ = 30 mm Hg.
    • Emergent neurosurgical consult.
  • Nerve root injury
    • Withdraw needle immediately.
    • If pain or motor weakness persists, start corticosteroids (Decadron 4 mg every 6 hours).
    • Electromyogram/nerve conduction velocity studies should be scheduled if pain persists.
  • Spinal headache
    • Keep the patient supine as tolerated.
    • Usually resolves within hours but can persist for days.
    • Hydration and caffeine may help ameliorate symptoms.
  • Aortic/arterial puncture
    • Withdraw needle immediately and keep the patient supine for 4–6 hours while monitoring hemodynamics.
    • Vascular surgery consult.