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EMedHome's Clinical Pearl

The Reflex and the Bradycardia

doi: 10.1097/01.EEM.0000550373.97695.74
EMedHome's Clinical Pearl

BY EMEDHOME.COM

The oculocardiac reflex is a trigeminal-vagal reflex that causes bradycardia with traction or compression of extraocular muscles. Its presence is an indication for urgent surgery in a patient with a so-called trapdoor type of orbital blowout fracture where the inferior rectus muscle is entrapped in the maxillary sinus. (Pediatr Emerg Care 2018 Feb 28. doi: 10.1097/PEC.0000000000001429; Emerg Radiol 2018;25[5]:561.)

The oculocardiac reflex occurs when there is traction on the extraocular muscles. The reflex is triggered by stimulation of the ophthalmic branch of the trigeminal nerve. This stimulus is transmitted via the ciliary ganglion to the medulla oblongata. The efferent portion travels with the vagus nerve and decreases firing of the SA node, leading to bradycardia, which can be profound. Activation of the oculocardiac reflex even creates a risk of cardiac arrest. (Pediatr Emerg Care 2018 Feb 28. doi: 10.1097/PEC.0000000000001429.)

Signs and symptoms of the oculocardiac reflex include a variety of arrhythmias (e.g., sinus bradycardia, junctional rhythm, bigeminy, asystole), nausea, vomiting, and headache. The reflex is greatly exaggerated in the presence of hypoventilation, hypoxemia, and acidosis, which can be seen in trauma. The degree of bradycardia worsens with progressive increase in the amount of traction on the ocular muscles; an attempted up-gaze causes additional stretch on the inferior rectus muscle, which can exacerbate bradycardia. (Pediatr Emerg Care 2018 Feb 28. doi: 10.1097/PEC.0000000000001429; J Oral Maxillofac Surg 2017;75:1716.)

This Clinical Pearl first appeared on EMedHome.com. Subscribers get a new clinical pearl emailed to them every Wednesday. Visit www.EMedHome.com.

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