Oculocardiac reflex is seen in which surgery: March 2007

Ans. B: Strabismus surgery The oculocardiac reflex/ Aschner phenomenon,/ Aschner reflex/ Aschner-Dagnini reflex, is a decrease in pulse rate associated with traction applied to extraocular muscles and/or compression of the eyeball. The reflex is mediated by nerve connections between the trigeminal cranial nerve and the vagus nerve of the parasympathetic nervous system. The afferent tracts derive mainly from the ophthalmic division of the trigeminal nerve. These afferents synapse with the visceral motor nucleus of the vagus nerve, located in the reticular formation of the brain stem. The efferent poion is carried by the vagus nerve from the cardiovascular center of the medulla to the hea, of which increased stimulation leads to decreased output of the sinoatrial node. This reflex is especially sensitive in neonates and children, and must be monitored, usually by an anaesthesiologist, during paediatric ophthalmological surgery, paicularly during strabismus correction surgery. However, this reflex may also occur with adults. Bradycardia, junctional rhythm, asystole, and very rarely death, can be induced through this reflex.