Intraoperative recording of nociceptive flexion reflex

Abstract

Hemodynamic responses to noxious stimuli during general anesthesia are regarded as signs of nociception. In this sense, modifications of intraoperative administration of opiates are made on clinical bases. However, recording of nociceptive flexion reflex (NFR), has been proposed as an objective tool in order to assess nociception/antinociception balance. To test the correlation between intraoperative NFR, hemodynamics modifications and range of opiates administration in patients undergoing spinal spinal/spinal cord surgery. The NFR was intraoperatively assessed in 15 patients during TIVA/TCI (10 subjects) or alogenates (5 pts.) anesthesia for spine surgery. In order to elicits NFR, the sural nerve was stimulated at the ankle (train of 5 stimuli, ISI 4 ms, intensity up to 100 mA): responses were recorded from the ipsilateral biceps femoris. In the alogenates group NFR was abolished. NFR threshold correlated with opiates administration changes in 6/10 patients. NFR threshold seems to correlate with nociception/antinociception balance. Further studies are needed in order to test the correlation between intraoperative changes of hemodynamic parameters, the amount of intraoperative opiates administration and postoperative pain.