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 ...