Effect of different anesthetic agents on oculocardiac reflex in pediatric strabismus surgery

Purpose: The oculocardiac reflex (OCR) occurs frequently during pediatric strabismus surgery. The aim of this study was to assess the effects of various anesthetic regimens on the incidence of OCR during the surgery. Methods: Two hundred and eighty children, 1 to 9 years old, undergoing elective strabismus surgery, were randomly assigned to eight groups; ketamine-sevoflurane (KS), ketamine-desflurane (KD), ketamine-propofol (KP), ketamine-remifentanil (KR), midazolam-sevoflurane (MS), midazolam-desflurane (MD), midazolam-propofol (MP), and midazolam-remifentanil (MR). No premedication was given. Anesthesia was induced using ketamine 1 mg·kg^-1 or midazolam 0.15 mg·kg^-1 with 66% N₂O in O₂. Laryngeal mask airways (LMAs) were placed with rocuronium 0.5 mg·kg^-1. Anesthesia was maintained with sevoflurane 2-3 vol. %, desflurane 5-6 vol. %, propofol 7-8 mg·kg^-1·h^-1, or remifentanil 0.75 μg·kg^-1 over 1 min, followed by a continuous infusion of remifentanil 0.5 μg·kg^-1·min^-1 with 66% N₂O in O₂. Heart rate (HR) was recorded during extraocular muscle (EOM) manipulation. OCR was defined as a reduction in HR of more than 20% induced by the traction of an EOM. Results: In patients given ketamine, OCR occurred more frequently in the KP (65.7%) and KR (62.9%) groups than in the KD (29.4%) and KS (37.1%) groups (P < 0.05). In patients given midazolam, OCR occurred more frequently in the MP (54.3%) and MR (60.6%) groups than in the MD (36.4%) and MS (31.4%) groups (P < 0.05). Conclusion: Propofol or remifentanil anesthesia was associated with a higher incidence of OCR during pediatric strabismus surgery than sevoflurane and desflurane anesthesia, when either ketamine or midazolam was used as an induction agent.