Oculocardiac reflex
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The oculocardiac reflex, also known as Aschner phenomenon, Aschner reflex, or 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, although tracts from the maxillary and mandibular division have also been documented[1]. These afferents synapse with the visceral motor nucleus of the vagus nerve, located in the reticular formation of the brain stem. The efferent portion is carried by the vagus nerve from the cardiovascular center of the medulla to the heart, of which increased stimulation leads to decreased output of the sinoatrial node[2]. This reflex is especially sensitive in neonates and children, and must be monitored, usually by an anaesthesiologist, during paediatric ophthalmological surgery, particularly during strabismus correction surgery[3]. However, this reflex may also occur with adults. Bradycardia, junctional rhythm, asystole, and very rarely death[4], can be induced through this reflex.
[edit] Treatment/prophylaxis
Removal of the inciting stimulus is immediately indicated, and is essential for successful termination of this reflex. The surgeon, or practitioner, working on the eye should be asked to cease their activity and release the applied pressure or traction on the eyeball. This often results in the restoration of normal sinus rhythm of the heart. If not, the use of an anti-muscarinic acetylcholine (ACh) antagonist, such as atropine or glycopyrolate, will likely successfully treat the patient and permit continuation of the surgical procedure. In extreme cases, such as the development of asystole, aggressive cardiopulmonary resuscitation may be required.
[edit] References
- ^ Lang S, Lanigan D, van der Wal M (1991). "Trigeminocardiac reflexes: maxillary and mandibular variants of the oculocardiac reflex.". Can J Anaesth 38 (6): 757–60. PMID 1914059.
- ^ Paton J, Boscan P, Pickering A, Nalivaiko E (2005). "The yin and yang of cardiac autonomic control: vago-sympathetic interactions revisited.". Brain Res Brain Res Rev 49 (3): 555–65. doi:. PMID 16269319.
- ^ Kim H, Kim S, Kim C, Yum M (2000). "Prediction of the oculocardiac reflex from pre-operative linear and nonlinear heart rate dynamics in children.". Anaesthesia 55 (9): 847–52. doi:. PMID 10947746.
- ^ Smith R (1994). "Death and the oculocardiac reflex.". Can J Anaesth 41 (8): 760. PMID 7923532.
[edit] External links
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