Pediatric emergency medicine trisk 1132
Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (172.85 KB, 4 trang )
reactive lymph nodes can also be mistaken for fluid collections. Lymph nodes
appear oval and hypoechoic with an echogenic hilum. When color flow is applied
to a lymph node the vascular stalk can be identified at the hilum, helping to
differentiate this hypoechoic structure from a fluid collection ( Video 131.31 ).
FIGURE 131.32 Muscle.
FIGURE 131.33 Cobblestoning in soft tissue.
Foreign-Body Identification and Removal
Ultrasound can be used for detection of radiolucent foreign bodies and accurate
real-time two-dimensional localization of all soft tissue foreign bodies. Real-time
sonographic visualization can guide percutaneous removal of a soft tissue foreign
body, minimizing surgical exploration.
Technique
The technique used for subcutaneous foreign body identification is similar to
evaluation for soft tissue infection. A high-frequency linear transducer is
preferred and the object should be identified in two planes. If an object is very
superficial, a water bath or a “stand-off pad” can be used to elevate the transducer
off of the area of interest, improving resolution. All soft tissue foreign bodies are
initially hyperechoic on sonography. The depth and size of the foreign body
should be measured and any relationship to surrounding nerves and vessels
should be noted. Surrounding granulation tissue, edema, or hemorrhage can
appear as a hypoechoic halo increasing visibility of the object. Typically objects
that are small or irregular, such as toothpicks or pencil tips, create clean shadows,
while objects with large smooth surface, such as glass or metal, create
reverberation artifacts such as comet tails. To remove a foreign body using realtime ultrasound guidance, the transducer should be placed so that the center
marker is over the foreign body and the skin should be marked to identify this
optimal incision site. After appropriate anesthetic injection and incision, image
the foreign body in the long axis and use forceps or hemostats to grasp the object
under ultrasound guidance.
FIGURE 131.34 Abscess.
Pitfalls
Bone and joint surfaces appear hyperechoic with shadowing, and can be confused
with foreign bodies if one is not familiar with the local anatomy. Scar tissue can
also appear hyperechoic and must be differentiated from foreign bodies. Wooden
foreign bodies may become less echogenic over time, making them more difficult
to see. Finally, using ultrasound dynamically to remove a foreign body is
technically challenging. It requires a moderate amount of ultrasound experience
and dexterity. The novice user may have greater success in identifying the foreign
body statically in multiple planes, marking the site and attempting removal in
standard fashion.
OTHER USES OF ULTRASOUND
There are other uses of sonography that are beyond the scope of this chapter. We
touch upon them briefly here to introduce the concepts. The interested reader
should consult a textbook of ultrasonography.
PARACENTESIS AND PERICARDIOCENTESIS
The need for these procedures is uncommon in pediatrics, but ultrasound can be
helpful in identifying the location of fluid and in avoiding injury to solid organs.
A phased array or curvilinear probe should be used for identifying fluid and for
dynamic ultrasound guidance. For paracentesis, the transducer should be placed
in different parts of the abdomen in order to identify the deepest pocket of fluid.
For pericardiocentesis, a small footprint probe will allow better visualization
between the ribs. Sonographic guidance allows a transthoracic approach rather
than the subxyphoid approach, which reduces the risk of injury to the liver.
EVALUATION OF JOINTS
Ultrasound can help with the detection or exclusion of joint effusion and can also
be used to guide arthrocentesis. The high-frequency linear probe is used.
Evaluation of the hip is discussed above. Ultrasound has also been used for the
knee, elbow, and shoulder.
NERVE BLOCKS
Nerve blocks may obviate the need for sedation for painful procedures, and may
decrease the amount of locally injected anesthetic. Ultrasound guidance for nerve
blocks can help prevent accidental puncture of neighboring vasculature and can
direct the needle tip to within close proximity of the desired nerve structures. A
linear high-frequency probe should be used. Ultrasound has been used to assist
with nerve blocks for the femoral nerve and the nerves of the forearm.
