Written by: Maurey Hajjar, MD, MPH (NUEM ‘22) Edited by: Justin Seltzer, MD (NUEM ‘21) Expert Commentary by: Alex Ireland, MD (NUEM '20)
Expert Commentary
Thank you to Dr. Hajjar and Dr. Seltzer for their excellent review of an underutilized ultrasound procedure.
After several challenging lumbar punctures during my residency training, I began to adopt this technique as a supplemental tool to improve first-pass success. When beginning, the patient can be placed in either the lateral decubitus or the upright position. However, I have found that in the patients for whom you are looking for ultrasound guidance, the anatomy due to body habitus is already challenging, and upright positioning offers the best advantage of maintaining midline.
There are several approaches to identifying your target with ultrasound, and my preferred strategy is different than the one mentioned in this post. After palpating the bilateral anterior superior iliac spines and drawing lines inward towards the midline, I start with my probe in the transverse view to identify the spinous processes at L3, L4, and L5. I mark above and below my probe at each process to identify the midline.
I then rotate the probe 90 degrees into a longitudinal view, but I keep my probe in the midline to identify contiguous vertebral spinous processes and the intervertebral or interspinous spaces between them. I place a mark on both sides of my probe with it aligned in the middle of this intervertebral space, which will be the exact insertion point of my needle.
Another key advantage of ultrasound is the ability to measure the anticipated depth of needle insertion. After identifying the spinous processes and intervertebral space in longitudinal view, I increase the depth and the gain to view the mixed echogenicity soft tissue and ligaments, and then see the hypoechoic subarachnoid space underneath the dura mater. I measure the depth of this space and then have an estimate of how far to insert the needle before obtaining cerebrospinal fluid.
Lastly, I would highly recommend attempting this technique on several “easy” patients where you can also readily palpate the anatomy. Similar to using a bougie during difficult intubations, we need to be skilled with our rescue techniques through diligent preparation and repeated practice.
References
Ultrasound Guided Lumbar Puncture. MGH Ultrasound.
Alex Ireland, MD
Emergency Medicine Physician
Vituity Group
Chicago, IL
How To Cite This Post:
[Peer-Reviewed, Web Publication] Hajjar, M. Seltzer, J. (2020, Dec 7). Ultrasound Guidance for Lumbar Puncture. [NUEM Blog. Expert Commentary by Ireland, A]. Retrieved from http://www.nuemblog.com/blog/ultrasound-imaging-for-lumbar-puncture
