Oculocardiac Reflex

The oculocardiac reflex (OCR), also known as the Aschner reflex or trigeminovagal reflex (TVR), was first described in 1908 as a reduction in heart rate secondary to direct pressure placed on the eyeball. It is defined by a decrease in heart rate by greater than 20% following globe pressure or traction of the extraocular muscles. The reflex most commonly results in sinus bradycardia. However, it also has a reported association with reduced arterial pressure, arrhythmia, asystole, and even cardiac arrest. This reflex has most notably been depicted during ophthalmologic procedures, more specifically during strabismus surgery; however, it also may be activated by facial trauma, regional anesthetic nerve blocks, and mechanical stimulation. The incidence of the oculocardiac reflex is reported to be anywhere from 14% to 90% and decreases with age, meaning pediatric patients are most at risk. Pediatric patients are also more susceptible to the detrimental consequences of this reflex secondary to having a greater dependency on heart rate to maintain cardiac output. The wide range of incidence and the severity of OCR is reportedly attributed to the effects of hypoxia, hypercarbia, acidosis, and the anesthetic agents used during surgery.