SGEM#41: Ultra Spinal Tap (Ultrasound Guided Lumbar Puncture)

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Date: June 16th, 2013

Case Scenario: A 66-year-old man presents with a 48 hour history of fever, lethargy and headache. No significant past medical history. On physical examination he has a temperature of 38.8C, GCS 15, stiff neck on flexion and no rash. Urinalysis and chest x-ray are normal. Laboratory testing reports an elevated white blood cell count with a left shift. You decide he needs a lumbar puncture to check for meningitis.

Question: Can ultrasound be used to improve successful LP attempts?

Background: The following procedures may decrease the risk of post-LP headache. Listen to SGEM#34: This is Spinal Tap for all the details.

Small-gauge atraumatic needles
Reinsertion of the stylet prior to the removal of the spinal needle
Mobilization of patients after completing the LP

Reference: Ultrasound imaging for lumbar punctures and epidural catheterisations: systematic review and meta-analysis. Shaikh F et al. BMJ 2013;346:f1720 doi: 10.1136/bmj.f1720

Population: 14 studies (n=1334)
Intervention: Ultrasound assisted LPs (5 studies) and epidurals (9 studies)
Control: Unassisted
Outcome: Reduction of failed attempts

Authors’ Conclusion: “Ultrasound imaging can reduce the risk of failed or traumatic lumbar punctures and epidural catheterizations, as well as the number of needle insertions and redirections. Ultrasound may be a useful adjunct for these procedures.”

Key Results:

Failed procedures 12 studies (n=1234) 79% RRR (95% CI: 57-90) NN 16 (95% CI: 12-25)
Traumatic Procedures 5 studies (n=?) 73% RRR (95% CI: 33-89) NN 17 (95% CI: 11-44)

BEEM Comments: There was no blinding for the patients. This might effect subjective outcomes such as post-LP headaches. It would be easy to do a sham ultrasound. However, the lack of blinding should not effect objectives outcomes such as failed or traumatic attempts.

Only 5 of 14 studies were done for LPs with the rest for epidurals. Half of the patients in the studies were obstetrical patients. All the physicians involved were ultrasound ‘keeners”. These things weaken the external validity of the results to the emergency department setting.

BEEM Bottom Line: There needs to be an adequately powered blinded RCT of ED doctors on consecutive ED patients in need of an LP showing a difference in patient oriented outcomes. Until then we suggest maximizing the methods proven to improve LP technique before we start adding unproven modalities (Straus et al).

Case Resolution: You successfully perform the LP without an ultrasound and send off the CSF to the lab for analysis to rule out meningitis.

KEENER KONTEST: The hoser who won last week was Constant Coolsma from the Netherlands. He knew that Tim Horton was a Canadian ice hockey defence man who later founded a coffee house/doughnut shop named after him.

Be sure to listen to this weeks podcast for another chance to a cool skeptical prize. Email your answer to TheSGEM@gmail.com. Use “Keener Kontest” in the subject line. First one to email me the correct answer wins.

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