The Effect of Bedside Ultrasonographic Skin Marking on Infant Lumbar Puncture Success: A Randomized Controlled Trial

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Study objective

Lumbar puncture is a commonly performed procedure, although previous studies have documented low rates of successful completion in infants. Ultrasonography can visualize the anatomic landmarks for lumbar puncture and has been shown in some studies to reduce the failure rate of lumbar puncture in adults. We seek to determine whether ultrasonography-assisted site marking increases success for infant lumbar punctures.


This was a prospective, randomized, controlled trial in an academic pediatric emergency department (ED). We enrolled a convenience sample of infants younger than 6 months between June 2014 and February 2016 and randomized them to either a traditional lumbar puncture arm or an ultrasonography-assisted lumbar puncture arm. Infants in the ultrasonography arm received bedside ultrasonography of the spine by one of 3 study sonographers before lumbar puncture, during which the conus medullaris and most appropriate intervertebral space were identified and marked. The lumbar puncture was then performed by the predetermined ED provider. Our primary outcome was successful first-attempt lumbar puncture. Subjects were considered to have a successful lumbar puncture if cerebrospinal fluid was obtained and RBC counts were less than 1,000/mm3. All outcomes were assessed by intention-to-treat analysis.


One hundred twenty-eight patients were enrolled, with 64 in each arm. No differences between the 2 arms were found in the baseline characteristics of the study subjects and providers, except for sex and first-attempt position. The first-attempt success rate was higher for the ultrasonography arm (58%) versus the traditional arm (31%) (absolute risk difference 27% [95% CI 10% to 43%]). Success within 3 attempts was also higher for the ultrasonography arm (75%) versus the traditional arm (44%) (absolute risk difference 31% [95% CI 15% to 47%]). On average, performing bedside ultrasonography on 4 patients (95% CI 2.1 to 6.6) resulted in 1 additional successful lumbar puncture.


Ultrasonography-assisted site marking improved infant lumbar puncture success in a tertiary care pediatric teaching hospital. This method has the potential to reduce unnecessary hospitalizations and exposures to antibiotics in this vulnerable population.

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