Effects of anesthetics on nociceptive sensory evoked potentials by intraepidermal noxious electrical stimulation of A-δ fibers

PURPOSE

Generation of nociceptive sensory evoked potentials (NEPs) by selective stimulation of nociceptive intraepidermal nerve fibers is a simple technique which could be used as intraoperative nociception monitor. We evaluated the effects of remifentanil, propofol and sevoflurane on NEPs by this technique.

METHODS

Patients undergoing general anesthesia were assigned to groups in two studies. A-δ fiber selective NEPs were recorded. Study 1: NEPs were recorded at control, under anesthetics administration: remifentanil at an effect-site concentration (Ce) of 1.0 ng/mL (n = 10), propofol at Ce of 0.5 µg/mL (n = 10), or sevoflurane at 0.2 minimum alveolar concentration (MAC) (n = 10), and recovery from the anesthetics. Study 2: NEPs were recorded at control and under administration of higher dose anesthetics: propofol at Ce of 0.5 and 1.0 µg/mL (n = 10) or sevoflurane at 0.2 and 0.5 MAC (n = 10). A P-value < 0.016 was considered statistically significant in multiple analyses.

RESULTS

Study 1: Remifentanil at Ce of 1.0 ng/mL significantly suppressed the amplitude of NEPs (mean amplitude (standard deviation) of control vs. remifentanil administration: 16.8 µV (3.8) vs. 10.1 µV (2.5), P < 0.001). Propofol and sevoflurane did not suppress the amplitude significantly. Study 2: Propofol at Ce of 0.5 and 1.0 µg/mL and sevoflurane at 0.2 and 0.5 MAC did not suppress the amplitude significantly.

CONCLUSION

The amplitude of A-δ fiber selective NEPs was suppressed by remifentanil but not propofol or sevoflurane. NEPs with intraepidermal electrical stimulation can assess the analgesic effect of anesthetics.

CLINICAL TRIAL NUMBER

UMIN000038214 REGISTRY URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000043328.

A new era for migraine: The role of calcitonin gene-related peptide in the trigeminovascular system

There is a huge improvement in our understanding of migraine pathophysiology in the past decades. The activation of the trigeminovascular system has been proved to play a key role in migraine. Calcitonin gene-related peptide (CGRP) and CGRP receptors are widely distributed in the trigeminovascular system. The CGRP is expressed on the C-fibers, and the CGRP receptors are distributed on the A-δ fibers of the trigeminal ganglion and nerves. Further studies found elevated serum CGRP level during migraine attacks, and infusion of CGRP can trigger migraine-like attacks, provide more direct evidence of the link between CGRP and migraine attack. Based on these findings, several treatment options have been designed for migraine treatment, including CGRP receptor antagonists (gepants) and monoclonal antibodies targeting CGRP or CGRP receptors. The clinical trials show both gepants and monoclonal antibodies are effective for migraine treatment. In this section, we describe the roles of the trigeminovascular system in migraine, the discovery of CGRP, and the CGRP signaling pathway.