Critically Appraised Topic: Does Ultrasound-assisted Lumbar Puncture reduce the number of LP attempts and adverse outcomes in Emergency Department Patients?

Study #1: This was a randomized control trial conducted in the emergency department (ED) of a teaching hospital of patients identified as candidates for Lumbar Puncture (LP). 80 patients were randomized into two groups of 40 with no statistically significant difference between groups by sex, mean age, and BMI. 80 patients was determined by a sample size calculation using Altman’s Nomogram with a power of 80%, and significance of 0.05. Control group: the LP was performed by the investigators using external palpation landmarking technique. Intervention group: the LP was performed by Ultrasound-guided (US) landmarking method. Patients were excluded if less than 18 years old or more than 60, pregnant, if they had a brain mass, infection over the puncture site, coagulopathy, or previous spinal surgery. The primary outcome measured was length of time of procedure. Secondary outcomes included were number of attempts, numbers of traumatic procedures, time of procedure, and patients' pain score during the procedure. Mean Time in minutes in the US group 3.3 with SD 1.2, Landmark group 6.4 with SD 1.2 (P= 0.032), Median number of attempts in the US group 1 IQR 1-2, Landmark group 2 IGR 1-3 (P=0.047), Pain score (0-10) in the US group 4.4 with SD 1.4, Landmark 7.4 with SD 1.1 (P=0.001). In regards to traumatic LP attempts this study showed, the number of traumatic attempts in the US group: 5, Landmark: 8 (P=0.024), suggesting US group had significantly fewer traumatic taps. A two-way ANOVA model was used to evaluate these outcomes with subgroups by BMI. BMI subgroups were BMI<25, BMI 25-29, BMI>29. Data from these subgroups showed less traumatic LP when US‐guided method used (two‐sided ANOVA, Bonferroni test, = 0.035).   


Study #2: This was a double-blinded, randomized, control trial conducted in the emergency department (ED) of a teaching hospital of patients identified as candidates for LP. Sample size included 46 patients with no difference between groups in mean age or BMI. The control group was 23 patients who underwent LP by palpation landmarking (PL). The intervention group underwent LP by the Ultrasound landmarking technique. Patients were excluded if less than 18 years of age, or those who refused to give consent. The primary outcome measure was number of failed LPs. Secondary outcomes included the number of attempts, procedure length, and ease of procedure, and patient comfort. These same outcomes were measured in subgroups of patients, defined as having a BMI>30. Results showed Ultrasound landmarks resulted in a significantly higher success rate. They were 1.32 times more likely to be successful than PLs (RR, 1.32; 95% confidence interval [CI], 1.01–1.72). In terms of secondary outcomes, there was no statistical difference in the number of attempts, traumatic LPS, or procedure length. In patients with a BMI>30, ​​the intervention group appears more successful than the control, with 4 out of 7 obese patients of the PL group had a failed LP versus the intervention group that had no failures (RR, 2.33; 95% CI, (0.99–5.49). However, this is not a statistically significant finding.  


Conclusions: Based on my review of the literature, I feel that it’s difficult to conclude that ultrasound-assisted LP has fewer failed attempts than the traditional LP technique, due to the small sample size of both studies. However, both showed statistically significant decreases in failed attempts using very similar protocols. Both protocol include the same landmarks for identification, which performs LPs at the same level of the spine L3-L4. As well, both used specifically trained ultrasound operators for LP. Using this similar methodology, further studies with larger sample sizes could shed more light on the efficacy and safety of Ultrasound-assisted Lumbar puncture. As for secondary outcomes, there is some suggestion in both studies that patients experienced less pain in the intervention group. The first study showed decrease adverse outcomes such as traumatic LP’s. As well as there seems to be potential benefit for patients with BMI greater than or equal to 30.  


  1. Mofidi M, Mohammadi M, Saidi H, et al. Ultrasound guided lumbar puncture in emergency department: Time saving and less complications. J Res Med Sci. 2013;18(4):303-307. 


  1. Nomura JT, Leech SJ, Shenbagamurthi S, et al. A randomized controlled trial of ultrasound-assisted lumbar puncture. J Ultrasound Med. 2007;26(10):1341-1348. doi:10.7863/jum.2007.26.10.1341.