Describe the oculocardiac reflex and its treatment.
The afferent pathway of the oculocardiac reflex begins with the long and short ciliary nerves, which transmit impulses to the ciliary ganglion followed by the Gasserian ganglion. The Gasserian ganglion sends impulses along the first division, ophthalmic division, of the fifth cranial nerve (trigeminal nerve) to the main sensory nucleus of the fifth cranial nerve in the floor of the fourth ventricle. The effer-ent pathway begins in the nucleus ambiguus, the motor nucleus of the vagal nerve, and transmits impulses to the vagal cardiac depressor nerves. Maneuvers that are most likely to evoke the oculocardiac reflex are tension on the extraocular muscles or pressure on the cornea. Retrobulbar block may both treat and evoke the oculocardiac reflex. This reflex manifests clinically as bradycardia with ventric-ular escape beats, nodal rhythm, or asystole. Treatment of these dysrhythmias is best initiated by requesting the surgeon to refrain from the maneuver that precipitated the reflex, such as traction on a muscle or severe scleral depres-sion during indirect ophthalmoscopy to examine the retina. Although the reflex will eventually fatigue, life-threatening bradycardic dysrhythmias can be pre-vented with small doses of intravenous atropine or gly-copyrrolate. Prophylactic intramuscular atropine or glycopyrrolate have generally not been successful in the prevention of the reflex when compared with intravenous dosing. The oculocardiac reflex may be more likely to occur under general anesthesia in the face of hypoxemia and hypercarbia.
Predisposing factors include hypoxemia, hyper-carbia, deep anesthesia, and light anesthesia. Persistent, nonfatiguing episodes may respond to retrobulbar anesthesia.