Oculocardiac reflex

Published on 07/02/2015 by admin

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Last modified 22/04/2025

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Oculocardiac reflex

Peter Radell, MD, PhD and Sten G.E. Lindahl, MD, PhD, FRCA

The oculocardiac reflex (OCR) was first described by Aschner and Dagnini in 1908. Recently, with the understanding that stimulation of the trigeminal nerve in areas other than the ophthalmic branch (V₁) can occur, a more comprehensive term, trigeminocardiac reflex, has come into use.

Anatomy

The afferent limb of the fifth cranial nerve is trigeminal, and the efferent limb is vagal. Specifically, afferent impulses travel via short and long ciliary nerves to the ciliary ganglion. From there, afferent information is sent to the gasserian ganglion via the ophthalmic branch of the trigeminal nerve (V₁). Efferent impulses leave the brainstem by way of the vagus nerve (X) (Figure 38-1).

Figure 38-1 Trigeminocardiac reflex pathway. Divisions of the trigeminal nerve: V₁, ophthalmic; V₂, maxillary; V₃, mandibular. ICA, Internal carotid artery.

Triggering stimuli

This reflex is triggered most commonly by traction on extraocular muscles (especially the medial rectus), direct pressure on the globe, ocular manipulation, and ocular pain. It may also be elicited by retrobulbar block, ocular trauma, and manipulation of tissue remaining in the orbital apex after enucleation. The reflex arc has even been described originating from other trigeminal afferent branches, for example, during sinus or nasal operations. The OCR seems to fatigue with repeated manipulation.

Manifestations

The most common manifestation of the OCR is sinus bradycardia. Other cardiac arrhythmias include ectopic beats, junctional rhythms, atrioventricular blockade, ventricular bigeminy, multifocal premature ventricular contractions, wandering pacemaker, ventricular tachycardia, and asystole.

Prevalence

The reported incidence of OCR during strabismus surgery is highly variable, ranging from 16% to 82%. The incidence is lower with the use of modern anesthetic agents, such as sevoflurane and desflurane, compared with older agents such as halothane. Children and young adults undergoing eye muscle operations under general anesthesia are the most susceptible to the development of OCR, but the incidence may also be increased in the elderly. Hypoxemia, hypercarbia, and acidosis increase the incidence and severity of the problem, and other risk factors include inadequate anesthetic depth and medication with β-adrenergic receptor blocking agents and potent opiates.

Intraoperative management

The OCR may occur during local or general anesthesia. Peribulbar blocks may help prevent arrhythmias by blocking the afferent limb of the reflex arc. However, the injection of the anesthetic agent may itself stimulate the OCR. Hemodynamic effects are generally self-limited but, in combination with other illness, can be serious; for example, OCR in combination with undiagnosed Epstein-Barr virus myocarditis has led to malignant ventricular arrhythmias, cardiac arrest, and subsequent death.

If a cardiac arrhythmia appears, the initial course of action is to notify the surgeon that orbital stimulation should be halted. Next, the depth of anesthesia and adequacy of ventilation and oxygenation are optimized. Commonly, heart rate and rhythm will return to baseline within 20 seconds after these measures are initiated. However, if the initial cardiac arrhythmia is serious or if the reflex recurs, atropine should be intravenously administered in 0.02-mg/kg increments (smaller doses may have no effect or a paradoxical effect, worsening bradycardia) until resolution is achieved.

During pediatric strabismus operations, many advocate the intravenous administration of atropine (0.02 mg/kg) or glycopyrrolate (0.01 mg/kg) before the extraocular muscles are manipulated. The use of glycopyrrolate, as compared with atropine, may be associated with less tachycardia, but glycopyrrolate has a slower onset of action.

Postoperative management

Onset time may be variable. For example, following retrobulbar block, the OCR may appear immediately or as late as 1.5 hours after an uncomplicated block. Retrobulbar hemorrhage can also result in delayed OCR because persistent bleeding gradually increases periocular pressure. Therefore, careful monitoring should continue for several hours after a suspected or known retrobulbar hemorrhage.

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