Oculo-cardiac Reflex during Strabismus Surgery

To evaluate the incidence of the oculo-cardiac reflex (OCR) and its associated risk factors during strabismus surgeries performed at a tertiary referral center between 1390 and 1392. Over a 2-year period, all strabismus surgery candidates were enrolled in the study after obtaining consent from the patients or their parents. Vital signs were recorded before the initiation of the surgery. While the depth of general anesthesia was controlled using the BIS instrument, the heart rate was recorded before and after muscle grasping. OCR was defined as a reduction of 15% or more in the heart rate caused by pulling extraocular muscle(s). Vital signs, especially heart and pulse rate, were monitored after recovery from anesthesia. Seventy-six patients (51.3% male subjects) with a mean age of 15±12 years (range: 2 to 55 years) were enrolled. The mean heart rate was 49±25 bpm (range: 44-152 bpm) before muscle grasping and 77±26 bpm (range: 30-152 bpm) at the conclusion of the operation (P<0.001). OCR occurred in 65 out of 76 (85.5%) patients and with 84 out of 173 (48.6%) operated muscles. The incidence of OCR was higher before 20 years of age; however, it showed a decreasing trend afterwards. OCR was more common during operation on cyclovertical muscles than horizontal ones (p=.02). Moreover, in surgeries on horizontal rectus muscles, OCR was more common if heart rate was more than 61 before surgery (p=.008). OCR was not significantly correlated with sex, type of disease, type of surgery, frequency of the surgery, and the order of operated extraocular muscles. The majority of patients undergoing strabismus surgery, especially younger subjects, those undergoing operation on the cyclovertical muscles and ones with a higher baseline heart rate, experience OCR during strabismus surgery. Due to the possibility of catastrophic consequences of OCR such as cardiac arrest, this matter deserves special attention.