Effect of different anaesthetic regimes on the oculocardiac reflex during paediatric strabismus surgery

The oculocardiac reflex (OCR) is induced by mechanical stimulation and ther efore is frequently encountered during strabismus surgery. This study was d esigned to determine how various anaesthetic regimes modulate the haemodyna mic effects of the OCR during paediatric strabismus surgery. Thirty-nine pa tients (4-14 years, ASA I) were randomized to one of four anaesthetic regim es: group P: propofol (12 mg.kg(-1).h(-1)) and alfentanil (0.04 mg.kg(-1).h (-1)); group S: sevoflurane 1-1.2 MAC in 30% O-2/70% N2O; group K: ketamine racemate (10-12 mg.kg(-1).h(-1)) and midazolam (0.3-0.6 mg.kg(-1).h(-1); g roup H: halothane 1-1.2 MAC in 30% O-2/70% N2O. Electrocardiogram (ECG), be at-to-beat heart rate (HR) and blood pressure (BP) changes were measured du ring and after a standardized traction was applied to an external eye muscl e (4-6 Newton, 90 s). OCR was defined as a 10% change in HR induced by trac tion. OCR occurred in 77% of patients. Whereas virtually all patients in th e P, H and S groups developed OCR, only 22% developed it in group K. Median HR change in group P (-37 bpm) was significantly greater (P < 0.05) than i n group H (-17 bpm) or group K (-7 bpm). Median BP change in group K (+10 m mHg) was significantly different (P < 0.05) from group H (-5 mmHg), group S (-3 mmHg) and group P (-8 mmHg). Atrioventricular rhythm disorders were si gnificantly more frequent in group P compared with group K (P < 0.02). Resp iration-induced sinus dysrhythmia was significantly less frequent (P < 0.00 1) in group K (0%), compared with group P (100%), group H (56%) and group S (55%). Of the anaesthetic techniques studied, ketamine anaesthesia is asso ciated with the least haemodynamic changes induced by OCR during strabismus surgery in paediatric patients.