Peribulbar Block for Prevention of Oculocardiac Reflex

Strabismus is a common ophthalmic problem in Egypt that usually requires surgical correction. This surgery primarily aims to improve alignment of visual axis but may be required only for cosmetic reasons. General anesthesia is mandatory for most cases however a concomitant local anesthetics administration is preferable to improve patient satisfaction, decrease postoperative analgesic requirements and reduce post-operative pain. Oculocardiac reflex is a noted serious complication that accompanies such surgeries and may be life threatening. Oculocardiac reflex (OCR) is one of the main challenges that face anesthesiologists during strabismus surgery. The incidence of OCR varies from 16 to 82 % in strabismus surgeries and this wide range does depend on the anesthetic agents, premedications, and the definition of OCR being used. Maintenance of adequate depth of anesthesia and the use of anti-cholinergic is the mainstay to reduce this risk. OCR is usually defined as a decrease in heart rate of more than 20 % from the baseline. This reflex is triggered by the pressure on the extra ocular muscles (EOM) or eyeball, orbital hematoma or trauma, the afferent limb is from orbital contents to ciliary ganglion then to the sensory nucleus of the trigeminal nerve near the fourth ventricle through the ophthalmic division of the trigeminal nerve. The main response of this reflex is transmitted through the vagus to the heart. This vagal stimulation leads to a decrease in heart rate (sinus bradycardia), contractility and arrhythmias such as atrioventricular block, ventricular fibrillation up to cardiac arrest. The incidence of the OCR decreases with age and tends to be more pronounced in young healthy patients. It has been suggested that the anesthetic agents used during surgery influence the incidence of OCR. To date, the only successful method to interrupt an OCR is to stop the EOM traction, and then proceed with caution as surgery continues. Depth of anesthesia is another presumed f