A 57 y.o. woman comes to ED with extreme SOB after a shoulder surgery that day.
The topogram from her PE protocol CT is shown below
what happened?
Our patient had diaphragmatic paralysis from her interscalene nerve block.
landmarks for the block
Interscalene blocks cause a decrease in forced vital capacity of 20-25% secondary to ipsilateral hemidiaphragmatic paralysis which usually resolves as the block wears off. Patients can be quite dyspneic. The mechanism of this paralysis is thought to be migration of anesthetic to the roots of cervical nerves 3,4 and 5 which enervate the diaphragm.
The anatomic course of the phrenic nerve runs in the fascia over the anterior scalene muscle. The block is given by placing 10 cc of anesthetic either in the brachial plexus sheath or near it. Both work well to anesthetize the shoulder and arm.
An elevated diaphragm is seen on the cxr with diaphragmatic paralysis. A sniff test can be done to watch the movement of the diaphragm on US when the patient inhales quickly. Lung function decreases when lying down if the diaphragm is paralyzed as opposed to a sitting position.
A goiter can cause diaphragmatic paralysis as well
The most common cause of diaphragmatic paralysis is injury to the phrenic nerve during surgery. Other etiologies for phrenic neve palsy include cervical whiplash injury, goiters, thoracic aortic aneurysm and mediastinal tumor or aberrant cervical vessels causing compression.
the stop light sign is the best landmark on US.
. Our patient improved when she sat up, her PE protocol CT was negative for CT and her block wore off. She was discharged home. io
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Kaufman M, Willekes L, Elkwood A, et al. Diaphragm paralysis caused by transverse cervical artery compression of the pnrenic nerve: the red cross syndrome. Clinical aNeurology and Neurosurgery. 20112 Vol 114(5):502-505.
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Shioya N, Inoue N, Kawashima N, et al. Enlargement of intrathoracic goiter with unilateral phrenic nerve paralysis leading to cardiopulmonary arrest. Intern Med. 2020 Sep 5;60(1):91-97.
https://www.acepnow.com/article/how-to-perform-ultrasound-guided-interscalene-nerve-blocks/2/