Effect of remifentanil on oculocardiac reflex in paediatric strabismus surgery

Background: Rapidly acting narcotics enhance the degree of bradycardia due to the oculocardiac reflex (OCR) elicited by extraocular muscle (EOM) tension during strabismus surgery. We evaluated and compared the effects of remifentanil and sevoflurane on OCR during paediatric strabismus surgery. Methods: One hundred and twenty children, 1-9 years old, undergoing elective strabismus surgery, were randomly assigned to receive sevoflurane or remifentanil. No anticholinergic prophylaxis was administered. Anaesthesia was induced using ketamine 1.0 mg/kg or midazolam 0.15 mg/kg with 66% N(2)O in O(2). Laryngeal mask airways were placed with rocuronium 0.5 mg/kg. Anaesthesia was maintained with sevoflurane 2.0-3.0 vol% with 66% N(2)O in O(2) or remifentanil 0.75 mu g/kg over 1 min and followed by the continuous infusion of remifentanil 0.5 mu g/kg/min with 66% N(2)O in O(2). Heart rate (HR) and blood pressure (BP) were measured and compared. OCR was defined as a reduction in HR of > 20% induced by traction of an EOM. Results: During anaesthesia, HR and BP were maintained at a lower level in the remifentanil group than in the sevoflurane group (each, P < 0.05). The mean percent change in HR (-23.3 +/- 17.0% vs. -11.2 +/- 13.0%; P < 0.05) and the incidence of OCR (58.3% vs. 28.3%; P < 0.05) following traction of an EOM were higher in the remifentanil group than in the sevoflurane group. Conclusions: Remifentanil enhanced the degree of bradycardia due to OCR as compared with sevoflurane during paediatric strabismus surgery.