Jordan Becker, MD, PGY-1
The article: “Ultrasound for Routine Lumbar Puncture.” Peterson, Michael A., et al. Academic Emergency Medicine, vol. 21, no. 2, 2014, pp. 130–136., doi:10.1111/acem.12305.
The idea: Ultrasound has been used in children and adults for a wide range of spinal imaging applications. In children, especially infants, ultrasound is used especially after failed lumbar puncture (LP) attempts to estimate the future success of another attempt. In adults, spinal ultrasound has been used purely for imaging studies, such as evaluation of spinal stenosis and intervertebral disc disease, as well as to guide placement of epidural catheters. These authors designed a randomized, controlled trial to address if routine use of spinal ultrasound prior to LP in adult emergency department patients would increase success, defined by their primary outcome of fewer needle insertion attempts during the procedure.
The study: Prospective, randomized controlled trial in adult emergency department patients requiring an LP. Patients >18 years old with any indication for LP were randomized to undergo traditional, landmark-guided needle placement vs. ultrasound-guided needle placement. An on-call ultrasound “teacher” would come to the bedside for patients randomized to the ultrasound group and teach the “operator” who would be performing the LP how to identify the interspinous space. Each operator had to have completed at least 10 successful LPs prior to this study.
Primary outcome: number of needle insertion attempts for success; “procedural success”, defined as >1mL CSF with <500 RBCs/hpf
Secondary outcome: time required for procedure and patient satisfaction
The results: 100 patients were successfully randomized into the study: 50 each in the ultrasound and landmark groups. “Procedural success” was obtained in 39 patients in the landmark group and 38 patients in the ultrasound group (78% and 76%, respectively; p=0.81). There was also no difference in the other primary outcome, needle insertion attempts. The authors reported a median of 3 attempts in the landmark group and 5 attempts in the ultrasound group (p=0.24). The authors reported, but did not show data, that there was no significant difference in any of the secondary outcomes either.
A post-hoc analysis of a subset of patients (n=51) with “difficult to palpate” or “unpalpable” landmarks also showed no difference in procedural success (62% in landmark, 77% in ultrasound group, p=0.25). Similarly, there was no difference in success in patients with high BMIs.
The takeaway: There is no advantage for the routine use of ultrasound in identifying interspinous spaces in all-comers for LP in the emergency department.