Written by Chris Thom
Spoon Feed
An ultrasound-assisted paramedian (USPM) approach to lumbar puncture (LP) was associated with a higher level of success, and fewer referrals to radiology for failed LP. See this video.
Avoid the bony spine by staying off the midline
This was a single center retrospective study of a hospitalist procedure service performing LPs. The study used a before and after design following a training intervention. Before the intervention, the LPs were almost exclusively done via landmark approach or occasionally via US assisted midline approach. The hospitalist group then received training in the USPM approach, and outcomes were compared between the two time periods.
Eighty-four patients were in the pre-training time cohort, and 185 were in the post training. BMI, age, and gender were similar between groups. In the pre-training cohort, 72.6% of LP attempts were successful compared to 85.4% in the post-training. This resulted in a 13.6% increase in success rate (95%CI 2.8%-24.4%, p=0.014). Radiology consultation for failed LP decreased from 25% in the pre-training group to 12.4% in the post-training.
How will this change my practice?
I am a strong believer that this is the way forward for LPs. Advantages include a larger intraspinal space compared to midline and the ability to guide the needle under active US imaging. The difference between my practice and this article was the use of an “US-assisted” approach versus the “US-guided” approach. These authors used “US-assisted”, which means a static approach to make the location and no active imaging for needle entry. I would strongly recommend the US-guided approach, as not being in midline allows for this to be done easily without bony obstructions. The trick, however, is the depth and angle of the needle make it difficult to track the needle accurately. However, if you are skilled with US guided vascular access, regional anesthesia, and arthrocentesis, then you are ready for this procedure.
POCUS pro-tips and clips:
The first step is to get acquainted with lumbar spine sonoanatomy. See below GIF and our new video! Briefly, you’ll identify the midline in the short axis, then rotate to the long axis / sagittal orientation with the spinous processes in view. Now slide the probe just to the left or right and angle towards midline by about 10 degrees. This should reveal the lamina and the associated gaps between them at each level. You’ll now be staring at the spinal canal, which is the goal location for your needle entry. Using active ultrasound guidance as in the GIF below, follow the needle into the spinal canal. Take out the stylet and you’ll be collecting CSF. The guesswork of “will there be CSF?” is now gone, as you know you are in the spinal canal before you remove the stylet.
Source
Increased lumbar puncture success using a paramedian approach: A retrospective cohort study. J Hosp Med. Published online July 21, 2025.
