Lumbar Puncture

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Indications & Contraindications

What are the indications for performing a lumbar puncture?

Diagnostic
  • Investigate meningoencephalitis
  • Investigate neurological disorders:
    • Multiple Sclerosis
    • Guillain Barre
    • Mitochondrial Disorders
    • Paraneoplastic Syndromes
  • Investigate subarachnoid haemorrhage
  • Investigate disorders of intracranial pressure
  • Administer diagnostic agents:
    • Contrast media in myelography
Therapeutic
  • Spinal anaesthesiaAdminister therapeutic agents:
    • Intrathecal chemotherapy
    • Intrathecal antibiotics
    • Intrathecal baclofen
  • Manage specific disorders:
    • Benign intracranial hypertension
    • Acute communicating hydrocephalus
    • Cryptococcal meningitis in HIV infection
    • CSF leak

What are the contraindications to performing a lumbar puncture?

Who should have a CT prior to an LP?

  • Focal neurological defecit
  • Papilledema
  • Reduced consciousness (GCS<12)
  • Immune compromise
  • Previous CNS disease
  • Recent seizures

Complications

What are the complications of lumbar puncture?

Immediate
  • Failure
  • Bloody tap
  • Nerve root pain
Early
  • Post-dural puncture headache (PDPH)
  • Post-dural puncture herniation (very rare)
  • Spinal / epidural haematoma
  • Spinal cord ischaemia
  • Nerve damage (temporary or permanent)
  • Infection:
    • Local injection site
    • Epidural abscess
    • Meningitis (rare)
Infective
  • Post-LP Back pain
  • Epidermoid tumour

What is post-dural puncture headache PDPH?

See section: Post-Dural Puncture Headache

What are the risk factors for PDPH following lumbar puncture?

Patient Related
  • Younger age (<40)
  • Female gender
  • History of headache
  • Fear of post-LP complaints
Procedure Related
  • Wide bore needle (<25G)
  • 'Traumatic' cutting bevel needle tip
  • Active withdrawal of CSF
  • Sitting position
  • Large volume fluid collection
  • Multiple attempts

Positioning & Puncture Site

Which position should the patient be placed for a lumbar puncture?

  • Correct positioning is key to procedural success
  • Two positions are can be used for lumbar puncture:


Lateral Recumbent

Sitting

Positioning
  • Left lateral position (for a right handed operator) with back along the edge of the bed
  • Head propped up on a single pillow to maintain a straight spine
  • Knees, hips and neck flexed in the foetal position to optimise interlaminar foramen
  • Hips and shoulders should lie vertically above each other
  • Sit patient on edge of bed with feet resting on a stool
  • Flex trunk by having patient lean forward clasping a pillow
Comments
  • First-line position for performing lumbar puncture
  • CSF pressure cannot be reliably measured in the sitting position
  • May be useful in patients with respiratory compromise

Which interspace should a lumbar puncture be performed at and how can this be identified?

  • Lumbar puncture should not be performed at or above the L2/3 interspace:
    • In adults, the solid spinal cord ends at L1 (ranges from T11 to upper L3)
    • At this level the conus medullaris continues distally as the cauda equina
    • Puncture above this level risks damaging the cord
  • The L4/5 or L3/4 interspace is usually used
  • The L4 spinous process can be estimated using Tuffier’s line:
    • An imaginary line drawn between the iliac crests
    • Significant anatomical variation exists between patients
  • Alternative anatomic landmarks include:
    • The tip of the scapula in line with T7 spinous process
    • The tip of the 10th rib in line with L1 spinous process
Surface landmarks for vertebrae

Procedure

How do you perform a lumbar puncture?

  • Sterile gloves
  • Sterile gown
  • Hat and mask
  • Sterile Drape
  • Chloraprep x2 (with 0.5% chlorhexidine)
  • Lidocaine
  • Syringe
  • 22G and 24G needle
  • Sterile gauze
  • Spinal Needle (22-25G atraumatic)
  • Manometer (40cm)
  • 3-way tap
  • Specimen pots x4
  • Dressing

Key Considerations
– Risk Assessment
– Consent
– Positioning

 

Risk Assessment

  • Confirm no undue bleeding risk:
    • Check coagulation and platelet screen
    • Confirm anticoagulant and antiplatelet medication stopped appropriately
  • Assess need for CT head prior to LP

 

Consent

  • Explain the risks of the procedure and complete a consent form
  • Complete a consent form 4 for ventilated patients

 

Positioning

  • Position the patient in the lateral recumbent position:
    • Knees to chest and back flexed as far as possible
    • Ensure one hip exactly above the other

 

    1. Identify insertion site at L4/5 interspace:
        • L4 in line with the top of the iliac crests (Tuffier’s line)
        • L3-4 interspace above may be used as an alternative

    2. Prepare sterile LP tray
    3. Ensure sterile technique:
      • Wash hands thoroughly
      • Put on sterile gloves, gown, mask, and hat

       

    4. Ensure sterile skin and surface:
      • Using chlorhexidine 0.5% to clean the skin at the insertion site
      • Allow to air dry
      • Drape the patient

       

    5. Infiltrate the skin and subcutaneous tissue with 1% lidocaine with a 25-gauge needle.
    6. If using a narrow gauge spinal needle Insert the introducer needle:
        • Direct the needle on a 10-degree angle toward the umbilicus
        • Should be introduced no more than 2/3-3/4 of the total length

       

    7. Insert the spinal needle and advance the needle slowly, removing the stylet every 2-3 mm to check for CSF flow:
      • Bevel should always enter facing upwards
      • A tactile click is usually felt as the needle tents and passes through the dura
      • If the patient complains of nerve root pain: Do not advance the needle, withdraw 2 mm, remove stylet and check for CSF. If none, then replace the stylet and remove

       

    8. Measure CSF pressure if required:
      • Rotate the needle 90 degrees counter-clock wise
      • Add 3 way stop-cock with tap closed to patient
      • Add monometer and open stopcock
    9. Collect CSF sample
      • Remove 1-2ml of CSF in each of the four tubes
      • Active CSF withdrawal using a syringe should only be performed when a patient cannot tolerate a long procedure.
      • Send samples to the lab as indicated.
    10. Turn needle 90-degrees clockwise and replace stylet prior to removal
    11. Cover with sterile dressing
  • Document the procedure in the patients notes
  • Assess patient for adverse reactions to procedure
  • Inform patient to monitor for signs of bleeding or infection
  • Post procedural analgesics as needed
  • Bed rest and oral fluid not specifically advised

Samples

How do you perform a lumbar puncture?

  • A general consensus is to label sample tubes sequentially from an LP
  • These can then be used for:

1st

2nd & 3rd

4th

0.5ml*
2.5ml each*
1ml*
  • Total protein
  • Glucose
  • Other biochemistries
  • Cell count & differential
  • Microbiological stains
  • Microbiological cultures•
  • Xanthochromia (Protect this sample from the light by placing it in a thick brown envelope outside the usual plastic specimen bag)
  • *1mL is about 20 drops from the Luer connector on a needle
  • A serum sample must be sent simultaneously for glucose and oligoclonal bands
  • *1mL is about 20 drops from the Luer connector on a needle
  • A serum sample must be sent simultaneously for glucose and oligoclonal bands

For more information on analysis of CSF see section:

See section: Cerebrospinal Fluid (CSF) Analysis

Spinal Needles

What are the key features of spinal needles?

  • Available in a variety of lengths:
    • Standard length is 75mm
    • Long needles (90mm) are available for obese patients
  • Available in variety of diameters (22-27G)
    • Smaller needles produce less damage to the dura and have a lower rate of PDPH
    • Larger needles have better flow rates making pressure measurements easier
    • Current consensus is that needle gauges of 22-25 are preferred for LP
  • Needle tip may be ‘cutting’ or ‘atraumatic’ in design
  • Introducer used with needles 25G and finer
  • Stylet used to prevent coring of tissue on insertion
  • Transparent needle hub allows early identification of CSF

What types of needle tips are available on spinal needles and what are their advantages and disadvantages?

Needle Type

Cutting

Atraumatic

Examples
Quincke
Atraucan
Sprotte
Whitacre
Ballpen
Advantages
  • Cuts through tissue and ligaments, making insertion easier
  • Aperture at the tip of the needle, so less likely to straddle the dural membrane if injecting medication - reduces the risk of failed spinals
  • Separates the longitudinal fibres of the dura without cutting them, causing less trauma
  • Reduces CSF leakage and hence PDPH rates
  • Generates a more convincing ‘click’ on breaching the dura
Description
  • Higher incidence of PDPH
  • Cutting tip potentially increases the risk of nerve damage
  • Less tactile feed back as it passes through the dura
  • Risk of tissue coring and aperture occlusion as no stylet is used
  • Small orifice increases resistance to CSF aspiration and injection
  • Orifice usually sits proximal to the tip and may straddle the dural membrane leading to failed spinal

What types of atraumatic spinal needles are commonly available for lumbar puncture and what are their advantages and disadvantages?

Needle Type

Whitacre

Sprotte

Ballpen

Profile
Description
  • Solid conical blunt tip
  • Rectangular lateral aperture just proximal to tip
  • Tapered blunt tip
  • Lateral aperture is larger, oval shaped and sits further from the tip than the Whitacre
  • Sharp stylet within the lumen of the hollow spinal cannula
  • Unlike other stylets, it protrudes 2–3 mm from the distal end of the spinal cannula with a smooth junction between the two.
Advantages
  • Blunt tip generates a more convincing ‘dural click’ on breaching the dura when compared to a cutting needle
    • Larger aperture for faster backflow of CSF into the hub on entering the subarachnoid space.
    • Less resistance to injection and aspiration
    • Tapered tip allows gradual and less traumatic separation of dural fibres, reducing PDPH rates compared to Whitacre needles
    • Opens at the distal tip of the needle, reducing the risk of injecting into the epidural space, as sometimes occurs with lateral aperture needles
    • No problems with coring of tissue or blockage of the aperture
    • The distance the needle tip needs to move into the subarachnoid space before CSF is seen is less, theoretically reducing the risk of neurological damage compared to Whitacre and Sprotte needles
    Description
    • Small lateral orifice increases resistance to CSF aspiration and anaesthetic injection
    • The orifice sits proximal to the tip, and may straddle the dural membrane, increasing the risk of spinal failure by inadvertent injection into the epidural space.
    • The lateral aperture is larger and a greater distance from the tip compared to the Whitacre - increases the risk of straddling the subarachnoid and epidural space at the time of injection and raising the likelihood of a failed or partial block
    • Withdrawal of the stylet may dislodge the hollow cannula from the subarachnoid space

    What types of cutting spinal needles are available for lumbar puncture and what are the advantages and disadvantages?

    Needle Type

    Quincke

    Atraucan

    Profile
    Description
    • Diamond-shaped cutting bevel and an opening at the tip
    • Double-bevel with a sharp initial bevel for creation of incision and a second bevel for the dilation of tissues
    Advantages
    • Cuts through tissue and ligaments, making insertion easier
    • Aperture at the tip of the needle, so less likely to straddle the dural membrane - reduces the risk of failed spinals
    • Causes less leakage of cerebrospinal fluid than Quincke needles
    • Aperture at the tip of the needle, so less likely to straddle the dural membrane - reduces the risk of failed spinals
    Description
    • Higher incidence of PDPH (8% vs. 3% for a 25G Whitacre needle)Cutting tip potentially increases the risk of nerve damage
    • Higher incidence of PDPH (8% vs. 3% for a 25G Whitacre needle)
    • Cutting tip potentially increases the risk of nerve damage
    • Less tactile feed back as it passes through the dura
    • No strong evidence that PDPH rates are comparable to atraumatic needles
    • May be associated with higher rates of post

    Applied Anatomy

    Which layers does a needle pass through during lumbar puncture?

    • Skin
    • Subcutaneous fat
    • Supraspinous ligament
    • Interspinous ligament
    • Ligamentum flavum
    • Epidural space
    • Dura mater
    • Arachnoid mater
    • Subarachnoid space
    Layers passed through when performing lumbar puncture or spinal anaesthesia

    Where does the spinal cord end?

    • Spinal cord ends at the conus medullaris
    • Level of conus traditionally considered to be lower in infants and children than adults – studies suggest median level is similar
    • Level of the conus medullaris varies significantly between individual patients:
    Upper Range
    Median
    Lower Range
    Adults
    T11
    L1
    L3
    Infants
    T12
    L2
    L4

    Which surface landmarks can be used to identify vertebral levels?

    • The L4 spinous process can be estimated using Tuffier’s line:
      • Significant anatomical variation exists between patients
      • An imaginary line drawn between the iliac crests
    • Alternative anatomic landmarks include:
      • The tip of the scapula in line with T7 spinous process
      • The tip of the 10th rib in line with L1 spinous process
    Surface landmarks for vertebrae

    Author

    The Guidewire
    Trainee in ICM & Anaesthesia

    Reviewer

    The Guidewire
    Trainee in ICM & Anaesthesia