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 durin g surgical correction of strabismus with a laryngeal mask airway and sponta neous respiration with sevoflurane or halothane inhaled anesthesia. Fifty-o ne children, 1-7 yr old, having outpatient strabismus correction were rando mized to sevoflurane (S) or halothane (H) in 66% nitrous oxide at 1.3 minim um alveolar concentration. Children breathed spontaneously through a laryng eal mask airway and were not pretreated with anticholinergics. The oculocar diac reflex (OCR), defined as a 20% decrease in heart rate (HR) from baseli ne, dysrhythmias, or sinoatrial arrest concomitant with ocular muscle tract ion 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 halothan e (S: 95 +/- 22 bpm, H: 73 +/- 19 bpm, P = 0.001). The incidence of dysrhyt hmias was higher in the halothane group (S: 4%, H: 42%, P = 0.004). Reducti ons 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%). Sevof lurane may be a more suitable anesthetic than halothane for operations invo lving traction on the ocular muscles with spontaneous respiration in childr en because of reduced incidence of OCR, airway irritability, and ventilator y 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 develope d anesthetic vapor, may reduce this problem when compared with the establis hed vapor halothane.