Pediatric emergency medicine trisk 4520 4520
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Pitfalls
It is important that clinicians are comfortable identifying the bladder and are able
to differentiate it from free fluid or fluid within bowel (Fig. 131.26 and
Video
131.27 ).
Lumbar Puncture Guidance
POCUS is a useful adjunct when performing lumbar punctures. Ultrasound can
readily identify landmarks such as the spinous process and interspinous space.
These landmarks can be challenging to palpate in infants, in whom the anatomy is
smaller, and in obese children, in whom the landmarks may be obscured by body
habitus. In infants, the spine is mostly cartilage; therefore, ultrasound can identify
deeper anatomy, including the spinal canal, conus medullaris and cauda equina
fibers. In all age groups, the ability to visualize the necessary landmarks may
improve success rates and lead to fewer traumatic lumbar punctures.
Technique
A linear transducer is recommended for imaging the spine. In obese children,
however, a curvilinear or phased array probe may be required to provide adequate
depth. The transducer should be placed on the spine in both the longitudinal and
transverse planes. In the longitudinal axis, the transducer should be placed along
the spine with the interspinous space in the center and a spinous process on each
side. In older children, the spine will appear hyperechoic with clean, anechoic
shadows posteriorly, and the interspinous space will appear darker (Fig. 131.27 ).
In the transverse axis, clinicians should move the probe up and down to ensure
the spinous process is midline and then identify the interspinous space before the
next spinous process appears ( Video 131.28 ). Clinicians can then mark the
interspinous space with a marker or object such as a paperclip. After marking the
area, sterile technique should be used.
In infants, both the longitudinal and transverse images will display more
anatomical structures than in older children. The spinous processes will still
appear hyperechoic, but because the bones are not completely calcified, sound
waves are transmitted through the spine to the spinal canal (Fig. 131.28 and
Video 131.29 ). Clinicians can visualize the dura mater, which appears
hyperechoic, and surrounds the anechoic cerebrospinal fluid. Within the spinal
canal, the conus medullaris and cauda equina fibers are also often visualized (Fig.
131.29 ).
