Alfentanil Blocks Reflex Pupillary Dilation in Response to Noxious Stimulation But Does Not Diminish the Light Reflex

Abstract

Dilation of the pupil in response to a noxious stimulus is a measure of opioid effect in isoflurane-anesthetized volunteers. In contrast, the pupillary light reflex is unaffected by alfentanil during isoflurane anesthesia. These data suggest that stimulus-induced pupillary dilation may be used to evaluate the analgesic component of a combined volatile and opioid anesthetic.