Proceedure :
1. Choose Preferred LP technique.
2. Locate The Puncture Site
The spinal cord ends at the L1 and L2 vertebral bodies. The desired sites for lumbar puncture are the interspaces between the posterior elements of L3 and L4 or L4 and L5. You can locate these spaces by palpating the iliac crest. Follow an imaginary line from the iliac crest to the spine. the interspace encountered is L4-L5.. Use it or the interspace cranial to it.
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Diagram Key - The orange lines represent the levels of the lumbar vertebra. - The spotted line is the imaginary line between the iliac crests that delineates the location in the midline of the inter-vertebral space.
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After locating the site of intended puncture, mark it by indentation of the skin with a fingernail.
3. Use Sterile Technique
Use sterile technique for the LP. Cleanse the skin with povidine-iodine solution after donning sterile gloves. Using sponges, begin at the intended puncture site and sponge in widening circles until an area of 10 cm in diameter has been cleansed. Drape the child beneath their flank and over the back with the spine accessible to view.
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4. Apply Local Anesthetic
Local anesthetic should be used in children older than 1 year of age. Anesthetize the site by injecting 1% lidocaine intradermally to raise wheal, then advance the needle into the desired interspace injecting anesthetic, being careful not to inject it into a blood vessel or the spinal canal.
5. Prepare The Spinal Needle
1. Check the spinal needle to ensure that the stylet is firmly in position, to prevent implantation of epidermoid tissue: have the stylet in place before advancing the needle.
2. Support the needle between your index fingers and stabilize the hub of the needle with your thumbs.
3. Grasp the spinal needle firmly with the bevel facing up toward the ceiling, making the bevel parallel to the direction of the fibers of the ligamentum flavum. The ligamentum flavum runs from vertebra to vertebra in a cranial to caudal orientation.
6. Puncture
1. With the needle perpendicular to the vertical plane but with the bevel pointed slightly cephalad, advance through the skin.
2. Advance slowly into the deeper structures until you detect a slight resistance on penetration of the spinous ligaments. The resistance continues until the needle penetrates the dura, at which time you will typically feel a "pop" sensation caused by the change in resistance. The pop indicates that you are in the subarachnoid space.
3. Remove the stylet.
4. Check for flow of spinal fluid.
5. If there is no CSF, rotate the spinal needle a few millimeters forward, then recheck. Repeat.
6. If the needle meets resistance, withdraw the needle with the stylet in place and reattempt the procedure. Verify that the puncture site is in the correct location. If it is, attempt a paramedian approach just a few millimeters lateral to the midline.