Lumbar Puncture

Question 1

Indications for LP

Answer 1

Diagnosis of central nervous system (CNS) infections
Monitoring response to antimicrobial therapy in CNS infections.
Diagnosis of metabolic diseases.
Administration of intrathecal medications.
(Controversial) CSF drainage in communicating hydrocephalus with IVH.

Question 2

Contraindications for LP

Answer 2

Increased intracranial pressure (ICP) due to mass lesions or bacterial meningitis.

Uncorrected thrombocytopenia or bleeding disorder.

Cardiorespiratory instability.

Skin or soft tissue infection at/near the puncture site.

Lumbosacral anomalies.

Question 3

What are potential complications from an LP?

Answer 3

Transient hypoxia due to positioning.

Contamination of CSF with blood from a traumatic tap.

Cerebral herniation from sudden intracranial decompression.

Infection (e.g., meningitis, epidural abscess, osteomyelitis, discitis).

Bleeding (e.g., hematomas, intraspinal hemorrhage).

Neurological damage (e.g., spinal cord puncture, nerve damage, abducens nerve palsy)

Question 4

What are the proper landmarks for LP insertion?

Answer 4

Palpate the interspace above or below an imaginary line between iliac crests (L3-L4 or L4-L5).

For preterm infants, use L4-L5 to avoid spinal cord injury.

Question 5

LP insertion technique

Answer 5

Clean the area with antiseptic and apply sterile drape.

If using lidocaine, inject 0.1-0.2 mL subcutaneously.

Insert needle in midline at a slight cephalad angle toward the umbilicus.
“Aim for Umbi”
Advance slowly until a “pop” is felt, indicating entry into the subarachnoid space (1-1.5cm)

Remove stylet periodically to check for CSF flow.

Question 6

CSF collection

Answer 6

Collect 0.5-1 mL (6 drops) in each sterile tube for laboratory analysis. Tube #1: Gram stain and bacterial culture
Tube #2: Glucose and Protein
Tube #3: Cell count and differential
Optional Tube #4: Rapid antigen tests for specific, suspected pathogens (ie: HSV PCR, Enterovirus)/Other studies

Question 7

Post-procedure care for LP

Answer 7

Replace stylet before withdrawing the needle.

Apply gentle pressure, clean the site, and apply a bandage.

Monitor for leakage, infection, or neurological changes.