What is the procedure for performing a lumbar puncture?

From the Guidelines

To perform a lumbar puncture, the most recent and highest quality evidence recommends using an atraumatic needle (≥22-gauge) and placing the patient in the lateral recumbent position to minimize the risk of adverse events, such as post-dural-puncture headache, which affects up to 35% of patients 1. The procedure involves positioning the patient in lateral decubitus or sitting position with knees drawn to chest to widen the intervertebral spaces. After identifying the L3-L4 or L4-L5 interspace (below where the spinal cord ends), the area is sterilized with antiseptic solution and draped. Local anesthetic (typically 1-2% lidocaine) is injected into the skin and deeper tissues. Using sterile technique, a spinal needle (usually 22-gauge or smaller with stylet) is inserted midline between the spinous processes and advanced slowly until a "pop" is felt as the needle penetrates the dura mater. The stylet is removed to check for CSF flow. Some key points to consider when performing a lumbar puncture include:

• Using an atraumatic needle to reduce the risk of post-dural-puncture headache, as conventional needles have been shown to have a higher risk of complications compared to atraumatic needles 1
• Placing the patient in the lateral recumbent position to minimize the risk of adverse events, although the sitting position may also be used depending on the physician and patient's condition 1
• Collecting less than 30 mL of CSF to minimize the risk of post-LP headache and other complications, as the volume of CSF withdrawn has been shown to have no significant effect on the risk of post-LP headache or back pain 1
• Avoiding multiple attempts (≤4) to minimize the risk of complications, as the risk of post-LP headache has been shown to increase with the number of attempts 1
• Using passive rather than active withdrawal of CSF to minimize the risk of post-LP headache, as active withdrawal has been shown to be associated with a greater risk of post-LP headache 1 The needle is removed, and a sterile bandage is applied. Patients can be mobilized immediately after the procedure, as prolonged rest has not been shown to reduce the risk of post-LP headache 1. Potential complications include headache, local pain, bleeding, infection, and rarely nerve damage. The procedure allows access to cerebrospinal fluid for diagnostic purposes in conditions like meningitis, subarachnoid hemorrhage, and multiple sclerosis.

From the Research

Procedure for Performing a Lumbar Puncture

The procedure for performing a lumbar puncture involves several steps and considerations, including patient positioning, to ensure a safe and successful outcome.

• Patient Positioning: The optimal patient positioning for lumbar puncture procedures has been studied, with research indicating that both lateral decubitus and upright positioning can yield equal success rates in emergency physicians and trainees 2. However, other studies suggest that the "sitting, feet supported" position may offer advantages for selected patients undergoing lumbar puncture, as it is associated with the widest interspinous distance 3.
• Technique and Indications: Lumbar puncture is a safe and simple procedure that can be performed with little risk of major complication if proper technique and indications are followed 4. It is indicated when CNS infection is suspected or to establish the diagnosis of subarachnoid hemorrhage when results of cranial computed tomography are normal.
• Contraindications: The major contraindication for lumbar puncture is elevated intracranial pressure with evidence of a mass lesion 4.
• Positioning for Specific Patient Groups: For children, the sitting position with flexed hips is recommended for lumbar punctures, as it maximally increases the interspinous space 5. Hip flexion in the sitting position can also anatomically optimize lumbar interspinous space width for needle passage in adults 6.
• Use of Ultrasonography: Ultrasonography may be a useful adjunct when performing lumbar puncture in the emergency department, particularly for measuring the interspinous distance and guiding needle placement 3, 5.