Pupillometry to detect pain r esponse during general anaesthesia following unilateral popliteal sciatic nerve block

Introduction Pupillary reflex dilation has been studied for nearly 20 years as a potential marker of response to noxious stimulation in volunteers and surgical patients. In response to an incision or tetanic electrical stimulation of the skin, pupillary reflex dilation monitoring permits the detection of a dramatic increase in pupil size, even during general anaesthesia. Marked differences in pupil size and reactivity have also been found following the noxious stimulation of centrally blocked and non-blocked segments during combined epidural and general anaesthesia. Moreover, pupillary reflex dilation was shown to be more sensitive when compared with other variables commonly used to assess response to noxious stimulation during general anaesthesia, such as heart rate and arterial blood pressure.