Lumbar Puncture

Indications

Contraindications

Absolute:

  • Coagulopathy
    • Therapeutically anticoagulated
    • Platelet dysfunction
  • Infection
  • ↑ ICP

Relative:

  • Hypovolaemia
  • Intracranial pathology
  • Spinal pathology

Anatomy

Surface anatomy:

  • The posterior iliac crests sit at L3/4 or L4/5 in most patients

Layers:

  • Skin
  • Subcutaneous fat
  • Supraspinous ligament
  • Interspinous ligament
  • Ligamentum flavum
    Thick and harder than other ligaments.
  • Epidural space
    Contains fat and blood vessels.
  • Dura
  • Subarachnoid space
    Contains spinal cord and nerve roots floating in CSF.
  • Spinal cord
    Ends at L2 in adults and L3 in children.
    • Puncture above these levels is associated with a risk of cord damage

Equipment

  • Adequate IV access
  • Oxygen
    If sedation is being used.
  • Monitoring
    • If performing regional anesthesia, ensure regular monitoring of:
      • Blood pressure
      • Respiratory rate
      • Conscious state
    • Additionally, ensure availability of:
      • ECG
      • Pulse oximetry
  • Infection control measures
    • Sterile field
    • Facemask
    • Gloves
    • Gown
  • Sterile prep
    Should be dried prior to insertion.
  • Local anaesthetic and syringe
    For skin. A 23G needle is preferred to a 25G as this is typically long enough to reach (and analgese) the supraspinous ligament.
  • Introducer
  • Spinal needle
    • Pencil point tips are demonstrated to reduce the incidence of PDPH
    • 25-27G needles are preferred for spinal anaesthesia
      • Smaller needles reduce the incidence of PDPH but also reduce the speed of CSF flow
      • Larger needles may be required in the case of calcified ligament
  • (Spinal anaesthetic syringe)
    Use the same volume of syringe each time, and of a different volume to the syringe used for skin LA.
  • (Manometer)
    If performing LP.
  • (CSF tubes)
    If performing LP.

Technique

  • Perform a block time-out
  • Position the patient
    • Sitting is typically easier as the sagittal plain is aligned
    • Lateral may be required for the uncooperative or sedated, or when measuring CSF pressures
    • Ensure maximal lumbar flexion
  • Sterile prep on patient
    Ideally by assistant. Ensure this has dried completely before proceeding.
  • Sterile scrub, gown, and glove
  • Draw up drugs
    • Skin LA
    • LA +/- opioid for spinal injection
  • Place sterile drape
  • Locate a suitable interspinous space
    • Feel for the protrusions of a spinous process
      Deep palpation may be required.
    • Running the thumb down the back can help identify where the optimal space is
  • Raise a skin weal of LA
    Typically the best insertion site is lower in the space.
  • Further injections of LA into ligament
    Use this opportunity to map the bony anatomy.
  • Place introducer into interspinous ligament
    Ensure that a dural puncture is not achieved in thin patients.
    • Perpendicular to skin is the ideal starting direction
  • Insert spinal needle through introducer
  • If bone is reached, with draw the spinal needle into the introducer and redirect the introducer
  • When a loss of resistance is felt, withdraw the introducer
    • Look for clear CSF flow
      This may take 20-30s in a small-gauge needle, especially if the patient is lateral. Replace the stylet and advance the needle further.
  • Once free-flow of CSF is obtained:
    • For diagnostic LP:
      • Attach manometer and measure fluid pressure
      • Then fill CSF tubes in series
        Typically 10 drops in each.
    • For spinal anaesthesia:
      • Attach syringe to spinal needle
      • Aspirate CSF
        Swirling of CSF within syringe should be seen.
      • Slowly inject local anaesthetic
      • Repeat aspiration during and at the end of injection
        • Ensures needle remained within CSF throughout and inadvertent epidural injection did not occur
        • Provides barbotage
          May achieve a more rapid onset and extent of block.

Troubleshooting Insertion

  • Unable to locate subarachnoid space
    • Ensure the patient is positioned correctly
      • No shoulder rotation
      • Sagittal planes are aligned
    • Adjusting needle direction
      • Redirect cranially
      • If still hitting bone, redirect cranially again
        Entering in the bottom of a space assists this approach, as the needle can be ‘walked-off’ the lower spinous process
      • Redirect caudally
    • Changing introducer position
      • Move the introducer ~0.5-1cm lower in the space
      • Place the introducer in a different space
    • Use a bigger spinal needle
      • Thinner needles are more flexible, and may divert their path away from calcified or hard parts of the ligament
    • Consider a lateral approach
  • Electrical or stabbing pain
    Needle has likely struck a spinal nerve root within the CSF.
    • Withdraw the stylet and monitor for CSF flow
    • If no flow, withdraw and readjust angle away from side of pain
  • Continuous flow of blood
    Needle is likely within an epidural vein.
    • Replace stylet and continue to advance

Complications

References

  1. Janik R, Dick W, Stanton-Hicks MD. Influence of barbotage on block characteristics during spinal anesthesia with hyperbaric tetracaine and bupivacaine. Reg Anesth. 1989 Jan-Feb;14(1):26-30.
  2. ANZCA. PS03: Guidelines for the Management of Major Regional Analgesia.