Distinct Neural Mechanisms Between Anesthesia Induction and Emergence: A Narrative Review

Abstract

Anesthesia induction and emergence are critical periods for perioperative safety in the clinic. Traditionally, the emergence from general anesthesia has been recognized as a simple inverse process of induction resulting from the elimination of general anesthetics from the central nervous system. However, accumulated evidence has indicated that anesthesia induction and emergence are not mirror-image processes because of the occurrence of hysteresis/neural inertia in both animals and humans. An increasing number of studies have highlighted the critical role of orexinergic neurons and their involved circuits in the selective regulation of emergence but not the induction of general anesthesia. Moreover, additional brain regions have also been implicated in distinct neural mechanisms for anesthesia induction and emergence, which extends the concept that anesthetic induction and emergence are not antiparallel processes. Here, we reviewed the current literature and summarized the evidence regarding the differential mechanism of neural modulation in anesthesia induction and emergence, which will facilitate the understanding of the underlying neural mechanism for emergence from general anesthesia.

Figure.

Sagittal section of the rodent brain showing the nuclei and circuits with selective modulation during anesthesia induction and emergence from general anesthesia. BF, basal forebrain; CMT^GABA, GABAergic neurons of the central medial thalamic nucleus; DRN^Ser, serotonergic neurons of the dorsal raphe nucleus; Iso, isoflurane; LC, locus coeruleus; LH^Orx, orexinergic neurons of the lateral hypothalamus; LHb^GABA, GABAergic neurons of the lateral habenula; OT^DA, dopaminergic terminals of the olfactory tubercle; PBN, parabrachial nucleus; PeFLH^Orx, orexinergic neurons of the perifornical lateral hypothalamic area; PFC, prefrontal cortex; PnO, pontine reticular formation; Pro, propofol; PVT^Glu, glutamatergic neurons of the paraventricular thalamic nucleus; SCN, suprachiasmatic nucleus; Sevo, sevoflurane; TRN^GABA, GABAergic neurons of the thalamic reticular nucleus; VP, ventral pallidum; VTA^DA, dopaminergic neurons of the ventral tegmental area.