Lumbar Puncture

From Guide to YKHC Medical Practices

written by Dr. Travis Nelson

Lumbar puncture (LP) is most commonly performed in the YKHC ER for evaluation of suspected meningitis in febrile infants, though is indicated in any patient with suspected meningitis or concern for ICH with negative CT.

Contraindications

The only absolute contraindication to LP is increased intracranial pressure, and a CT head or ophthalmologic examination for papilledema should precede LP in any patient where there is concern for increased ICP*.

Severe thrombocytopenia (< 50k platelets) or coagulation factor deficiency are relative contraindications, though LP may still be indicated depending on degree of clinical concern for meningitis. Performing an LP in this setting increases risk of spinal hematoma or intracranial hemorrhage, and under such circumstances, consultation with hematology may help guide management.

  • Sx of acutely increased ICP in children: headache, vomiting, AMS, papilledema, HTN with bradycardia, pupillary changes, fluctuating GCS (UpToDate Symptoms of ICP)

If your patient is in any distress, specifically respiratory, the procedure should be deferred until they have been stabilized. If they are being medevac'd to Anchorage, this may not happen until they have arrived at the receiving hospital.

Complications

Without ICH or bleeding diathesis, lumbar punctures are generally low risk. There is a theoretical risk of introducing meningitis, though with sterile technique this risk is exceedingly low. There is a risk of spinal cord injury, this is again rare and typically, neurologic deficits are transient.

Post dural puncture headaches (PDPH) are common (~10%) in children and adults, and no technique has been found that consistently mitigates the risk of headache. Most mild PDPH headaches can be treated with analgesics, while persistent or severe headaches are treated with epidural blood patch.

Technique

Lateral spine.png

The key to successful LPs is positioning! While adults may be placed in seated position or lateral decubitus position, positioning infants in seated position is technically difficult and infants are generally positioned in the lateral decubitus position. If you need an opening pressure, you will also need to place the patient in the lateral decubitus position. For infants it is recommended to place a hard board under the infant to better gauge infant’s midline. In my experience failure of LP in adults is typically due to directing the needle too cranially or caudally. Since infant spinal levels are easy to palpate but subarachnoid space is small relative to adults, failure of LP in infants is rather from directing the needle too far laterally from midline. Positioning is key! Ensure you have an assistant who is able to hold the infant’s position for you - - most ER techs are expert at this task.

  1. feel for bony landmarks: midline spine at the level of the iliac crests correlates to L3/L4 interspace in most individuals. I typically mark my anticipated interspace with an indentation using my fingernail.
  2. thoroughly cleanse skin with chlorhexidine or povidone-iodine.
  3. drape patient with sterile drapes.
  4. place an 18-22 gauge needle in the L3/L4, L4/L5 or L5/S1 interspaces. Most procedure guides recommend directing the needle towards the patient’s umbilicus. You will know you are in the ligamentum flavum when you are able to take your hand off the needle and not have it change position. For older children and adult patients there is typically a tactile ‘give’ when the needle pushes through the dura mater and into the subarachnoid space, however for infants this is not usually felt. For infants I typically push the needle in ~ 1 cm, then remove the stylet and if there is no fluid adjust as needed. Always replace the stylet before moving the needle to decrease the risk of epidemoid tumor formation.

For infants try to collect at least 0.5-1 cc of CSF in each of three tubes. If you have high suspicions for meningitis or the patient has been pre-treated with antibiotics and risk of nothing growing on culture media, obtain a 4th tube to be sent for PCR (this can be sent with the Medevac crew to Anchorage to expedite transport). Once sufficient fluid is obtained insert the stylet and remove the needle, a simple bandaid is typically sufficient for covering the insertion.

Troubleshooting

  • Dry tap: Make sure your patient is well hydrated! I typically will give at least one IVF bolus to any infant that I am going to perform an LP on to try to mitigate this, and to ensure good flow, but this is not common practice. If tap is unsuccessful, redraw the needle to skin then reinsert in either a more cranial or more caudal direction. If still unsuccessful, redraw the needle to skin and reinsert in whichever direction you didn’t try last time. If unsuccessful on three attempts, I withdraw the needle completely and move to a different spinal level and start over.
  • Bloody tap: If blood-tinged CSF, typically this is fine. Although the preliminary studies will be difficult to interpret the culture will still be obtained. If frank blood then remove the needle, get a new needle, and reattempt at a different spinal level.

Resources/References


Common ED Procedures