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Increasing Your Odds of a Successful LP

Larry Mellick, MD, Ann Dietrich, MD, and Solomon Behar, MD

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Sol, Ann and Dr Larry Mellick discuss tips for improving your success rates with infant LP’s.


  • For best success with infant Lumbar Puncture(LP) do the procedure sitting with the hips flexed, a good hold and good local anesthesia.

  • What are the rates of failed lumbar punctures(LP) and what can we do to improve this? In training centers 20-30% of all LPs are going to be traumatic but success rates of an experienced practitioner are much better.

  • What position should we be performing LP in? Having the child sit up is the preferred method for Mellick though most people are doing them in the lateral decubitus position.

    • One benefit of the seated position is that we do not need to worry as much about oxygenation while performing the procedure. Some of this disadvantage of the decubitus position can be offset by pre-oxygenation.

    • Ultrasound studies have shown that the interspinous space is larger in the seated position than the lateral decubitus position. In this position the neck does not need to be flexed but the head needs to remain midline.

    • The landmarks including the iliac crest are more obvious in the seated position and it is easier to confirm that no rotation is occurring.

  • You do not suggest flexing the neck, is there any part of the baby that should be flexed to open up this space? Flexion at the hips will be beneficial to opening up the space.

    • One way to do this is to put sheets under the legs but not the buttocks of the child. This improves flexion at the hips and gives you more space to work with. Additionally the persons supporting the child can rest their arms on the sheets.

  • What about the early stylet removal technique? The early stylet removal techniques involves puncturing the skin and soft tissue with the stylet in place then removing the stylet before further advancing the needle.

    • The reason that a stylet is used is that a normal needle can introduce epidermal tissue and lead to an epidermoid cyst down the road. Once you are through this tissue the stylet is no longer needed for this purpose. By removing the stylet early you can get the needle plugged with fat but on the balance this technique will improve your chances of success.

    • Nigrovic LE et al. Risk factors for traumatic or unsuccessful lumbar punctures in children. Ann Emerg Med. 2007 Jun;49(6):762-71. PMID: 17321005

  • Does dehydration matter? Should we re-hydrate infants prior to attempting LP? There was a recent study of this showing that an IV fluid bolus does not change the size of the subarachnoid space on ultrasound.

    • Rankin J et al. Intravenous Fluid Bolus Prior to Neonatal and Infant Lumbar Puncture: A Sonographic Assessment of the Subarachnoid Space After Intravenous Fluid Administration. JAMA Pediatr. 2016 Mar;170(3):e154636. PMID: 26954534

  • Does the quality of the hold matter? Yes it is important for the person holding the child to maintain good hip flexion and a still position. Anesthesia will help with this role.

  • Does anesthesia matter? Yes. There are better success rates when anesthetic is used. In Mellick’s experience is that it is easier to feel the needle go through the dura when injected lidocaine is used than when it is not.

Videos by Dr. Mellick on how to perform and improve your success rates in infant LPs can be found here and here.

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Trouble with the Cord Full episode audio for MD edition 170:56 min - 80 MB - M4AHippo Peds RAP October 2016 Summary 542 KB - PDF