Blowout Fracture and the Oculocardiac reflex
Sep 04, 2024
When you're suspicious of entrapment in an orbital floor blowout fracture following trauma, you ask your patients to look up, to check for diplopia. Do you cardiac monitor them when you do this?
Patients with no diplopia, with an orbital floor blowout fracture, are assumed to have no entrapment. However, even with no diplopia, the oculocardiac reflex can identify a group of patients that still require surgical intervention. It is a rare finding, but one to know.
We discussed the oculocardiac reflex in this blog back in January of 2014 in an article titled; Aschner phenomenon in traumatic enucleation of the eye. In that case a 35 yo patient presented following being stabbed in the eye with a stick. The patient presented with loss of vision in the eye and profound bradycardia.
The Aschner phenomenon, which is due to the oculocardiac reflex, is mediated by the vagus nucleus and leads to the negative chronotropic effects on the heart, resulting in bradycardia, which may be so significant, that syncope occurs.
Recently, a case in Emergency Medicine News was brought to my attention by Dr Joe Nemeth. It describes a child with an injury to the eye resulting in an inferior orbital blowout fracture, and the emergency physician is asked to check the oculocardiac reflex.
The oculocardiac reflex has a more significant effect in children with facial fractures and especially inferior blowout fractures and can result in severe bradycardia. A positive reflex is considered to be a fall in heart rate of > 10 beats per minute when looking upwards for approximately a minute. It is a result of entrapment, resulting in increased pressure in the orbital contents. It is important to perform the test, because if positive when a blowout fracture is identified, it indicates entrapment and the patient will probably require surgical repair.
References
- Brandt, Robert MD. A Tip You May Not Know for Orbital Blowouts. Emergency Medicine News 46(9):p 1,22, September 2024. | DOI: 10.1097/01.EEM.0001052168.50477.a6
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