Comparative effects of different anesthetic regimens on the oculocardiac reflex

Background: The oculocardiac reflex (OCR), which is most often encountered during strabismus surgery in children, may cause bradycardia, arrhythmias, and cardiac arrest following a variety of stimuli arising in or near the eyeball. The main purpose of this study was to evaluate the effects of various anesthetic regimens on modu lation of the cardiovascular response of the OCR during strabismus surgery. Patients and Methods: Three hundred American Society of Anesthesia (ASA) physical status I-IIpatients, scheduled for elective strabismus surgery under general anesthesia, randomly allocated in a double blind fashion to one of three anesthetic regimens of group P ( propofol 2 mg/kg, alfentanil 0.02 mg/kg, and atracurium 0.5 mg/kg at induction) , group K (ketamine racemate 2mg/kg, alfentanil 0.02 mg/kg, and atracurium 0.5 mg/kg at induction) and group T (thiopental 5mg/kg, alfentanil 0.02 mg/kg, and atracurium 0.5 mg/kg at induction. Mean arterial pressure (MAP) and heart rate (HR) were recorded just before and at 1, 15, 30, 45, and 60 min after induction. OCR was defined as a 20 beats/min change in HR induced by traction compared with basal value. Results: Mean heart rate (± SD) during the course of surgery in group P was significantly slower than in the K group (111.90 ± 1.10 vs. 116.7 ± 0.70 respectively, P < 0.05) .Mean HR changes (± SD) in group K was signifi-cantly higher than in P group (11.2 ± 1.44 vs. 8.7 ± 1.50 respectively, P < 0.05). Mean arterial pressure changes (± SD) were significantly lower in group P than in group K or T patients (12.5 ± 1.13 vs. 19.3±0.80 or 18.9±0.91 respectively, P < 0.05). Frequency of OCR was significantly lower in group K than group T or P patients (9% vs. 16% or 13% respectively, P < 0.05). Conclusion: Induction of anesthesia with ketamine is associated with least cardiovascular changes induced by OCR during strabismus surgery.