Basic step-by-step instructions are below. Consider printing this for your trainees right before your LP.
Watch the video below for a more detailed explanation of the technique
Lumbar Puncture Tips and Tricks
If Bone is Encountered
- It’s common to encounter bone while looking for a path to the CSF
- When bone is encounter, leave the needle in place, and carefully assess the alignment of the needle
- Check if the needle is angled too far to the right or left. US can help confirm that you are in the midline.
- Palpate or use ultrasound to see if the needle is too close to one of the spinous processes
- Once you determine which direction to wish to re-angle your needle, slowly withdraw the needle tip into the subcutaneous tissue, then adjust your angle
- It is impossible to re-adjust the angle when the needle is anchored in the dense spinous ligaments. This will bend the needle
- When re-advancing the needle take note how deep the needle travels
- If you encounter bone, but your needle traveled deeper than before, you are headed in the right direction. Pull back into the subcu, then take a slightly steeper angle in the same direction. You may be able to “walk down” the spinous process into the CSF
- On your new needle pass, if you encounter bone at a shallower depth you have angled the wrong direction. Trying angling the needle the opposite direction.
- If no CSF is encountered after 3- needle passess
- Take out the needle
- Re-palpate and re-ultrasound the landmarks
- Consider moving up or down to another interspinous space
- Often after encountering bone several times, a small amount of bleeding occurs which can clot and clog the needle
- If blood ever comes out of the hub of needle, or if no CSF is found after several needle passes, remove the needle and flush it with saline
Patient Position is Critical
- Adjust the height of the bed so your elbows are bent at 90 degrees while performing the procedure
- Lateral DecubitusThis is the preferred position to measure opening pressure, and if the patient cannot sit upright due to weakness, altered mental status, etc.
- Have the patient move as close to you at the edge of the bed as safely possible
- Make sure the spine is perpendicular to the hips and shoulders (see image below). Placing a pillow under the head and between the knees is helpful
- Maximal flexion of the neck, back, and knees maximally widens the space between the spinous processes. Get the knees as close to the chest as possible
- Sitting Upright
- This position may increase the success of the LP
- This position maximally increases the space between spinous processes
- Sitting with the feet supported on a chair and the patient maximally curled forward leaning on pillows in their lap
Optimizing CSF Flow
- About 2 cc/tube is needed for basic LP labs (glucose, protein, cell count + diff, bacterial Cx, and HSV PCR)
- Additional studies require more CSF
- Up to 40 ml of CSF can safely be removed at a time, but large volumes will likely cause a temporary headache.
- Once CSF is encountered, you may be able to increase flow by:
- Asking the patient to gently straighten their legs
- As a drop of CSF is hanging from the needle, touch the drop with the inner surface of the collection tube. This will wick the drop into the tube and increase capillary flow
- Increase intra-abdominal pressure with a cough or valsalva
- Rotating the needle 90 degrees
- Never aspirate CSF as there is a theoretical increased risk of bleeding
Don’t Let the Lab Throw Away your Specimen
- The lab is mandated to dispose of improperly labeled specimens
- Place a patient sticker on ALL 4 tubes of CSF
- Mark them with your initials, date, and time
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1. Straus, S.E., Thorpe, K.E. & Holroyd-Leduc, J. How do I perform a lumbar puncture and analyze the results to diagnose bacterial meningitis? JAMA 296, 2012-22 (2006).
2. Ellenby, M.S., Tegtmeyer, K., Lai, S. & Braner, D.A.V. Lumbar Puncture. New England Journal of Medicine 355, e12 (2006).