Pain monitoring in anesthetized children: first assessment of skin conductance and analgesia-nociception index at different infusion rates of remifentanil

Background Analgesia and nociception can not be specifically monitored during general anesthesia. Movement of the patient or hemodynamic variations are usually considered as symptoms of insufficient analgesia. The measure of skin conductance (SC) allows an assessment of peripheral sympathetic activity. The analgesia-nociception index (ANI) provides an evaluation of the parasympathetic activity based on heart rate variability. These two non-invasive monitors might allow a better assessment of perioperative nociception. Objectives Describe the profiles of SC and ANI after a standardized nociceptive stimulation, in anesthetized children, at different infusion rates of remifentanil. Materials/Methods For this pilot study, 12 children (8.4 +/- 5 years) scheduled for middle-ear surgery were anesthetized with desflurane to maintain a bispectral index at 50. Remifentanil was used for analgesia, at an initial infusion rate of 0.2 mu g.kg-1.min-1. Remifentanil infusion rate was then decreased: Five steady-state periods of 10 min were obtained at 0.2, 0.16, 0.12, 0.08, and 0.04 mu g.kg-1.min-1. At the end of each period, a standardized tetanic stimulation was applied to the patient. Variations in heart rate, blood pressure, SC, and ANI were recorded before and after each stimulation. Results After the stimulation, ANI was significantly decreased compared with prestimulation values for all remifentanil infusion rates. This decrease was greater at 0.04 mu g.kg-1.min-1 than at the other infusion rates. SC, heart rate, and blood pressure were not modified by the stimulations, whatever the dose of remifentanil. Conclusion ANI might provide a more sensitive assessment of nociception in anesthetized children than hemodynamic parameters or skin conductance.