Lumbar puncture

CONTRAINDICATIONS TO LUMBAR PUNCTURE

  • Focal neurological signs and depressed level of consciousness.
  • Clinical signs of raised intracranial pressure, or impending cerebral herniation:
    • deep coma, i.e. GCS < 9, or sudden deterioration of level of consciousness,
    • decerebrate or decorticate posturing,
    • neurogenic hyperventilation,
    • unequal dilated or poorly reactive pupils,
    • absent doll’s eye reflex,
    • papilloedema.
  • Haemodynamic/respiratory unstable patients.
  • Clinical meningococcaemia (septicaemia) with petechiae/purpura. (confirm with skin scrape, Gram stain and blood culture).
  • Skin sepsis or abnormalities over the lumbar puncture site.
  • Coagulopathy.
  • Spinal anatomic abnormality.
  • Acute paraplegia.
  • Status epilepticus.

PROCEDURE

  • Positioning and restraint are vital in determining the success of the procedure.
  • The ability of the assistant in restraining is as important as the skill of the ‘operator’.
  • Preparation entails not only positioning, but attention to sedation/analgesia, ‘patient comfort’ and safety, as well as factors such as adequate lighting.
  • Resuscitation equipment must be available at bed side.
  • Pay attention to the sterility of the operating field.
  • Local analgesia with/without sedation may be required. See Chapter 20: Pain Control, Management of pain .
  • Ensure that all necessary equipment, e.g. needles, manometers and specimen tubes are close at hand.
  • Only the interspaces below L3 (L3/L4 or L4/L5) are used in order to avoid damaging the conus medullaris.
  • With the patient in the lateral recumbent position, the L3/L4 interspace is found at the level of the line joining the highest points of the two iliac crests.
  • Turn the bevel of the needle (with stylet) to face the patient’s side to avoid cutting the longitudinal dural fibres.
  • As the needle is advanced, the first ‘give’ or loss of resistance is encountered with the piercing of the ligamentum flavum. A slight ‘popping’ sensation is felt as the needle penetrates the dura. Remove the stylet to allow CSF to drain out passively. If no fluid appears, then rotate the needle a quarter turn (90°). If this does not help, replace the stylet and advance the needle a few millimetres and then check for fluid as before.
  • Measure the opening pressure using a manometer, with the child relaxed in the lateral decubitus position. In a young relaxed child, the opening pressure is in the range of 60 –180 mm H₂O.
  • At the end of the procedure, re-insert the stylet before removing the needle completely.

Note:
If intracranial infection is suspected, do a blood culture and initiate antimicrobial treatment immediately. Refer to Chapter 8: Infective/Infectious Diseases, Meningitis, Acute Bacterial .

Remember to catch a few drops of CSF on a labstick to check the glucose and for the presence of white cells which may give an indication of an infection.