Effects of an infratrochlear nerve block on reducing the oculocardiac reflex during strabismus surgery: a randomized controlled trial.

PURPOSE: To determine whether an infratrochlear nerve block (ITB) can reduce the oculocardiac reflex (OCR) during strabismus surgery on the medial rectus muscle (MR).

METHODS: This prospective, randomized single-masked study included 60 patients with intermittent exotropia scheduled for unilateral MR resection/lateral rectus recession under general anesthesia. Patients were randomly allocated to receive a regional nerve block of the infratrochlear nerve (ITB group) prior to surgery or standard treatment without a nerve block (control group). The OCR was defined as a sudden decrease in heart rate of ≥ 15% from baseline. Changes in heart rate (HR) and the incidence of the OCR were measured during the three stages of surgery applied to the MR in each group: conjunctival incision, muscle dissection, and muscle traction.

RESULTS: There were no intergroup differences in patient demographics or baseline HR. The mean HRs during conjunctival incision, muscle dissection, and muscle traction were 94, 90, and 96 bpm, respectively, in the ITB group, and 85, 68, and 84 bpm in the control group; the corresponding OCR incidence rates were 3, 20, and 10%; and 7, 87, and 38%. The HR was higher and the OCR incidence was lower in the ITB group than in the control group during muscle dissection and traction (all p < 0.05).

CONCLUSIONS: An ITB maintains a stable HR and reduces the OCR during surgery on the MR. The ITB is less invasive and easily accessible to a surgeon, and can help improve the safety of strabismus surgery.