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What is the Optimal Position for Successful Lumbar Puncture?

February 24, 2023

Written by Julie Brown

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This randomized controlled trial demonstrated that lateral decubitus position was statistically the same as the upright position for lumbar puncture success.

Why does this matter?
Although lumbar punctures are quite commonly performed, it is not uncommon for proceduralists to require multiple attempts. Unsuccessful LPs can lead to delayed diagnoses, delayed treatment and antimicrobial administration, prolonged hospitalizations, and increased morbidity for patients. Authors in this study aimed to investigate if one positioning technique (lateral decubitus versus upright) was superior in achieving a successful LP.

Any way you want it, that’s the way you need it?
This was a randomized, prospective trial conducted at a Level I trauma center that included a sample size of 116 adult and pediatric patients who underwent lumbar puncture for a variety of indications. LPs were performed primarily by Emergency Medicine residents (a few were performed by Pediatrics residents) and supervised by board-certified EM physicians. Patients were randomly assigned to either the lateral decubitus or upright position after study enrollment. Following the procedure, the proceduralist self-reported data including the number of needle insertions, needle redirections, repositioning requirements, change of proceduralist, and prior experience of the proceduralist. The primary outcome was successful LP, defined as obtaining a CSF sample of at least 1.5 mL in five or fewer attempts.

LP was performed successfully in 85.5% (95%CI 73.8-92.4%) of the lateral decubitus group compared to 80.3% (95%CI 68.7-88.4%) of the upright group, a 5.2% difference*. There was no difference in the number of needle re-insertions or redirections, first-pass success rate, procedure failures, and contaminated samples between groups.

Classic instruction advises lateral decubitus positioning as the optimal technique for successful LP and is the preferred positioning for obtaining opening pressure measurements. This study suggests that upright positioning is similarly successful, if not otherwise contraindicated. Trainees should be instructed in both positioning techniques to optimize procedural success, including ultrasound localization of landmarks.

Is Lateral Decubitus or Upright Positioning Optimal for Lumbar Puncture Success in a Teaching Hospital? J Emerg Med. 2023 Jan 11;S0736-4679(22)00527-3. doi: 10.1016/j.jemermed.2022.09.002. Online ahead of print.

*Nerd’s Corner: They based the sample size calculation on the hypothesis that lateral decubitus position would be 5% more successful; alpha 0.05, power 0.9; sample size per authors = 116. I am not a statistician, but I get a sample size of 2,424 when I do this calculation; maybe I am doing it wrong. Lateral decubitus was 5.2% better than upright, but was that statistically significant? Oddly, the authors don’t report this, which is unfortunate, since that is the primary outcome. When I run the calculation, it shows that it was not statistically different: difference 5.2% (95%CI –8.9265% to 18.7694%, p = 0.4610). Those with stats skills/software will want to independently confirm this. ~Clay Smith

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