A comparison of the incidence of the oculocardiac and oculorespiratory reflexes during sevoflurane or halothane anesthesia for strabismus surgery in children

We examined changes in the cardiorespiratory system of small children during surgical correction of strabismus with a laryngeal mask airway and spontaneous respiration with sevoflurane or halothane inhaled anesthesia. Fifty-one children, 1-7 yr old, having outpatient strabismus correction were randomized to sevoflurane (S) or halothane (H) in 66% nitrous oxide at 1.3 minimum alveolar concentration. Children breathed spontaneously through a laryngeal mask airway and were not pretreated with anticholinergics. The oculocardiac reflex (OCR), defined as a 20% decrease in heart rate (HR) from baseline, dysrhythmias, or sinoatrial arrest concomitant with ocular muscle traction occurred less frequently with sevoflurane than with halothane (S: 38%, H:79%, P = 0.009). The baseline HR was higher with sevoflurane (S: 114 +/- 13 bpm, H: 101 +/- 15 bpm, P = 0.002). The lowest WR occurred with halothane (S: 95 +/- 22 bpm, H: 73 +/- 19 bpm, P = 0.001). The incidence of dysrhythmias was higher in the halothane group (S: 4%, H: 42%, P = 0.004). Reductions in minute ventilation and PETCO2 accompanied OCRs. Airway irritability was present with halothane only (S: 0, H: 3). Eleven children, of whom the majority had received halothane, required measures to correct Spo(2-) < 95% or PETCO2 > 60 mm Hg during maintenance anesthesia (S: 11%, H: 32%). Sevoflurane may be a more suitable anesthetic than halothane for operations involving traction on the ocular muscles with spontaneous respiration in children because of reduced incidence of OCR, airway irritability, and ventilatory disturbances. Implications: Some children experience a sudden slowing of the heart and impaired breathing when the surgeon pulls on the eye muscles during squint operations under anesthesia. Sevoflurane, a recently developed anesthetic vapor, may reduce this problem when compared with the established vapor halothane.