Oculocardiac reflex: afferent path
Anatomy, Clinical - Neurologic
In 1908, Aschner described a decrease in heart rate as a consequence of applying pressure directly to the eyeball. This phenomenon would eventually be termed “the oculocardiac reflex” and is defined clinically as a decrease in heart rate by 10% following pressure to the globe or traction of the ocular muscles. The reported incidence of the oculocardiac reflex varies from 14% to 90%, depending on the study, making it relatively common. (Dewar KMS. The Oculocardiac Reflex. Proc. Roy. Soc. Med. 1976; 6: 13-14. Chung CJ, Lee JM, Choi SR, Lee SC, Lee JH. Effect of remifentanil on oculocardiac reflex in pediatric strabismus surgery. Acta Anaesthesiol Scand 2008; 52: 1273-1277.)
Trigeminal Nerve (ciliary ganglion to ophthalmic division of trigeminal nerve to gasserian ganglion to the main trigeminal sensory nucleus). Also afferent tracts from maxillary and mandibular divisions of trigeminal nerve have been documented.
Vagus Nerve (afferents synapse with visceral motor nucleus of vagus nerve located in the reticular formation and efferents travel to the heart and decrease output from the sinoatrial node).
Triggered by traction on the extraocular muscles (especially medial rectus), direct pressure on the globe, ocular manipulation, ocular pain.
Can also be triggered by retrobulbar block (pressure associated with local infiltration), ocular trauma, or manipulation of tissue in orbital apex after enulcleation.
It is also important to note that a globe need not be present for the reflex to occur and there are reported cases of reflex bradycardia with tense orbital hematoma following an enucleation procedure. (Dewar KMS. The Oculocardiac Reflex. Proc. Roy. Soc. Med. 1976; 6: 13-14.)
Reflex fatigues with repeated stimulation.
Most commonly leads to sinus bradycardia, but may also lead to junctional rhythm, ectopic beats, atrioventricular block, ventricular tachycardia, and asystole.
The incidence of the oculocardiac reflex decreases with age and tends to be more pronounced in young, healthy patients, which is clinically significant for pediatric aanesthesiologists as it is observed with greatest incidence in young healthy neonates and infants undergoing strabismus surgery. (Yi C, Jee D. Influence of the anaesthetic depth on the inhibiton of the oculocardiac reflex during sevoflurane anesthesia for pediatric strabismus surgery. Brit. Journ. Anes. 2008; 101(2): 234-238.)
Hypoxia, hypercarbia, acidosis, and light anesthesia can worsen the severity of the OCR.
As the oculocardiac reflex is a vagal response, clinicians have attempted to abolish the vagal stimulation of the heart using atropine and gallamine. Of the two anticholinergic medications used, there appears to be less bradycardia with atropine as opposed to gallamine, 0% vs. 5% incidence, respectively. (Dewar KMS. The Oculocardiac Reflex. Proc. Roy. Soc. Med. 1976; 6: 13-14.)
Some clinicians have also attempted to minimize or reduced the effect of the reflex by inducing very deep anesthesia, which appears to be clinically significant at BIS values below 50. (Yi C, Jee D. Influence of the anaesthetic depth on the inhibiton of the oculocardiac reflex during sevoflurane anesthesia for pediatric strabismus surgery. Brit. Journ. Anes. 2008; 101(2): 234-238.)
Others have attempted to use short acting opioid narcotics, i.e. remifentanil, to abalate the response to ocular pressure and have reported this to actually increase the incidence and severity of the reflex. (Chung CJ, Lee JM, Choi SR, Lee SC, Lee JH. Effect of remifentanil on oculocardiac reflex in pediatric strabismus surgery. Acta Anaesthesiol Scand 2008; 52: 1273-1277.)
May occur during both local and general anesthesia.
The retrobulbar block may prevent arrythmias by blocking the afferent limb, but may also stimulate the OCR with pressure of local injection.
Notify the surgeon to stop orbital stimulation.
Optimize oxygenation and ventilation. Prevent light anesthesia.
If arrythmia/bradycardia does not resolve consider atropine 20 mcg/kg IV (or glycopyrrolate).
The OCR may occur as much as 1.5 hours after a retrobulbar
Retrobulbar hemorrhage can result in delayed OCR as persistent bleeding gradually increases periocular pressure.
Monitor carefully in the PACU if suspected retrobulbar hemorrhage.