Lumbar Puncture

Lumbar puncture (LP) is a bedside procedure I occasionally do as an intensivist to obtain a sample of cerebrospinal fluid (CSF) surrounding the spinal cord and brain. CSF analysis can help diagnose central nervous system pathologies like infections, autoimmune disorders, malignancy, etc. Pictured is the Safe-T PLUS Adult Lumbar Puncture Tray I use.

Safe-T PLUS Adult Lumbar Puncture Tray

After positioning the patient (lateral decubitus or upright), I’ll palpate the lumbar spinous processes (goal is L3-L4 which is distal to the conus medullaris). In certain situations, I’ll use ultrasound to identify additional bony structures, the interspace, and the general trajectory to the subarachnoid space. After cleaning and draping the procedural site, I’ll use a 25G needle to create a skin wheal with 1% lidocaine, followed by a 22G needle to anesthetize the deeper tissues and locate bony landmarks.

Using a 20G styletted spinal needle, I’ll traverse the skin → subcutaneous tissue → supraspinous ligament → interspinous ligament → ligamentum flavum → epidural space, and ultimately enter the subarachnoid space confirmed by free-flowing CSF when removing the stylet. This technique is primarily done by “feel.”

Next, I attach the manometry tubing (with the manometer already on the stopcock) and allow the manometer to fill with CSF. Once the fluid column has stabilized (there will be some variation due to breathing), I’ll record this “opening pressure.” Then I’ll drain this CSF from the manometer into a collection tube. If needed, I’ll turn the stopcock to obtain more CSF from the patient. Once I’m finished, I’ll remove the needle and dress the site.

As a cardiothoracic anesthesiologist, I also perform lumbar CSF drains using a very similar approach to place a catheter in the CSF to measure pressure and drain fluid over many days.

Drop me a comment below with your experiences and questions!

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