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PEM Pearls: Perfecting your pediatric lumbar puncture using ultrasound

2017-10-26T14:33:32+00:00

lp_collect-croppedA lumbar  puncture (LP) is a common procedure that every emergency physician must master. Pediatric LPs can be challenging for even the most experienced clinician due to small anatomy, difficulty with patient cooperation, and lack of frequency performed. A successful procedure is defined by obtaining cerebrospinal fluid and/or performing a non-traumatic lumbar puncture. There are multiple variables that lead to a successful pediatric lumbar puncture including provider experience, use of anesthesia, and patient positioning. Success rates for pediatric lumbar punctures are variable, with a large range from 34%-75%.1

Role of Ultrasound

Ultrasound has been shown to help identify both pediatric  and adult anatomy and optimal patient positioning for the procedure.2,3 In pediatric patients, it can also be used to identify the thecal canal width and determine optimal entry angles.1 Similarly, ultrasound has been shown to lead to higher confidence scores in identifying pediatric LP insertion point than traditional landmark technique alone.4

How to perform an ultrasound-guided LP in a pediatric patient:

  1. Use a high frequency linear transducer set at a depth of 3-5 cm.
  2. Position the patient for the procedure in an upright or lateral decubitus position. NOTE: It is important to remember that any adjustment in position will alter ultrasound-guided markings after this step.
  3. Palpate for the iliac crests to look for your ultrasound starting point at the L4 intervertebral space
  4. Start with the transducer in longitudinal view and identify the following structures: spinous processes, vertebral bodies, dura, subarachnoid space, and conus medullaris.
  5. Measure the distance from skin to dura using the calipers on the ultrasound screen to help guide lumbar needle distance.
  6. While in a longitudinal view, mark the intervertebral space superior and inferior to your target site with a surgical pen.
  7. Obtain transverse views of the same structures to help confirm the midline and intervertebral spaces. This view will help you triangulate the optimal insertion site. Mark your target site with a surgical pen.
  8. With your patient now appropriately positioned with an optimally identified and marked intervertebral space, proceed with usual sterile techniques to perform the LP.
1.
Vitberg Y, Tseng P, Kessler D. The Sonographic Appearance of Spinal Fluid at Clinically Selected Interspaces in Sitting Versus Lateral Positions. Pediatr Emerg Care. August 2016. [PubMed]
2.
Ferre R, Sweeney T. Emergency physicians can easily obtain ultrasound images of anatomical landmarks relevant to lumbar puncture. Am J Emerg Med. 2007;25(3):291-296. [PubMed]
3.
Warhadpande S, Martin D, Bhalla T, et al. Use of ultrasound to facilitate difficult lumbar puncture in the pediatric oncology population. Int J Clin Exp Med. 2013;6(2):149-152. [PubMed]
4.
Kim S, Adler D. Ultrasound-assisted lumbar puncture in pediatric emergency medicine. J Emerg Med. 2014;47(1):59-64. [PubMed]
Ashley Foster, MD

Ashley Foster, MD

Chief Resident
UCSF-SFGH Emergency Medicine Residency Program
Delphine Huang, MD

Delphine Huang, MD

Resident
Department of Emegency Medicine (EM) UCSF-San Francisco General Hospital EM Residency Program
Aaron Kornblith, MD

Aaron Kornblith, MD

Assistant Clinical Professor
Department of Emergency Medicine & Pediatrics
University of California, San Francisco