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The usual goal of lumbar puncture (LP) in children is to obtain cerebrospinal fluid (CSF) to test for markers of infection. Measuring opening pressure is not necessary, and therefore the procedure is straightforward. The condition of children with hypoxemia, respiratory distress, hypotension, and tachycardia may deteriorate when they are positioned for LP, so resuscitation and empiric administration of IV antibiotics is needed prior to LP. In children with thrombocytopenia or factor deficiencies, replace platelets or factor before attempting LP.

Anticipate the procedure and its difficulties. Assemble a needle of the correct size, the appropriate specimen containers and preprinted labels, and ensure a quiet environment without interruptions. Explain the procedure to the caregivers. In some institutions, written informed consent for LP is required. Describe the process of procedural sedation if it is needed and obtain consent.

Apply a topical anesthetic cream or spray prior to needle insertion to reduce pain and improve the success rate of the LP.1,2 For infants, sucking on a pacifier dipped in sucrose solution is analgesic, calming and decreases crying. Prepare the skin using sterile technique.

Have an experienced health care provider, the “holder,” restrain the infant or child. Wrapping the child in sheets may help limit leg movement. Flexing the hips is more important than flexing the neck. In addition, flexing the neck may lead to respiratory difficulty. Whether to choose the lateral recumbent position or the sitting position depends upon the preference of the physician. In one study using US to measure the width of the spinous processes, the sitting position was found to be better than the lateral decubitus position.3 Although the sitting position may improve flexion of the hips, this position may be more difficult for the holder to maintain.

Most LPs are performed with a 22-gauge LP needle, usually 11/2 in. in length for infants, 21/2 in. for children 2 years to 8 years, and 31/2 in. for older children. In obese patients, choosing an LP needle may be more difficult. One study calculated that an LP needle length (in centimeters) of 1 + [17 × (weight in kilograms/height in centimeters)] was most accurate.4 LP depth was measured on abdominal CT scans to derive this formula. Lumbar needles with a clear hub show CSF flow sooner than those with metal or opaque hubs.

Insert the LP needle between the L4 and L5 spinous processes, in the intervertebral space, in the midline of the back, and direct the needle toward the umbilicus. This interspace is easily located because it lies in line between the iliac crests. Introduce the needle with the bevel of the needle up. Insert the needle until the characteristic “pop” identifies introduction into the subarachnoid space. An alternative method is to remove the stylet from the needle5 after the needle pierces the skin. Advance the needle, without the ...

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