Lumbar Puncture

Indications

1. Diagnostic: Meningitis, subarachnoid hemorrhage, Guillain-Barre syndrome, leukemic infiltration.
2. Therapeutic: Spinal anesthesia, antibiotic administration, cancer chemotherapy.
3. Investigational: Myelography.

Contraindications

• Raised intracranial pressure.
• Spinal cord compression due to vertebral disease (caries, collapse, IVDP).
• If the history suggests the possibility of an intracranial bleed, a CT scan should always be performed prior to LP, if scanning facilities are available.
• Local infection at the site of LP.
• If meningitis is suspected LP should be done even if increased ICT is present, especially so when there are no lateralizing signs and there is delay in getting a CT scan.

Anatomy

• The spinal cord terminates at the level of L1/L2 and ideal sites for lumbar puncture is between the spines L3/L4.
• The point can be identified where the line joining the highest point of the iliac crests crosses the spine.

Technique

Left Lateral Position

• Arrange the patient with hip and knee flexed in the true left lateral position on the edge of the bed. (Pre-medicate irritable and restless patients with very slow IV diazepam).
• Support the right arm and right leg with pillows to ensure that the position is maintained and to counteract the tendency for the patient to roll over.
• Under strict aseptic precautions, cleanse the area with antiseptic solution.
• Infiltrate the skin over the midline with 1% plain lignocaine and screen with sterile drapes.
• Again, check and confirm the position.
• Forefinger and thumb resting on the spines of L3 and L4 respectively, introduce 20G spinal needle and stylet with bevel upmost. Fine bore (24G) preferred to avoid post LP headache.
• Advance the needle between the spinous processes and through the dense interspinous ligament.
• Check to see that the needle remains at 90° to the spine. If the line is correct, advance the needle tip through the tough ligamentum flavum to enter the subarachnoid space with a distinct ‘giving way’ at a depth of 4-5 cm. Remove the stylet and wait for CSF to emerge. If this does not occur, rotate the needle gently.

A. Patient in the lateral decubitus position with back at edge of bed and knees, hips, back and neck flexed

• If fluid is not obtained, replace the stylet and repeat after advancing the needle no further than 0.5 cm.
• Withdraw the needle to skin and repeat the procedure, rechecking the alignment of the needle with spine if:

a. bony resistance is encountered

b. a nerve root is hit

c. venous blood is obtained

• Do not have more than three attempts in any single interspace before either obtaining assistance from a senior colleague or proceeding to the L2 – L3 interspace.
• Collect the CSF, (after noting the pressure with a manometer) sufficient for the CSF examination.
• Remove the needle and cover the puncture site with a small sterile dressing (if the CSF is blood stained, centrifuge a sample to see if there is xanthochromia).
• Sitting Position
• Sitting position should be tried in a patient with scoliosis or following unsuccessful attempts in the lateral position.
• Position the patient comfortably, straddling a chair and leaning forward to ensure that the spine is well flexed.
• Support the patient’s outstretched arms with pillows. Proceed as above, but do not measure the CSF pressure in this position.

After Care and Complications

• Instruct the patient to lie prone for 4 hours with the foot end of the bed elevated.
• If headache subsequently develops, return the patient to bed for a further 12 hours (post-LP headache increases on sitting up and is relieved on lying down). If the CSF pressure is found to be very high (>250 mm), monitor the patient closely.
• Record:
• Pupil size and light reflexes
• Pulse rate
• Respiratory rate
• Blood pressure
• Conscious level.