Non-pharmacological Auditory and Somatosensory Stimulation in Anesthetic Emergence

General anesthesia is an indispensable component of modern surgical practice. While its induction mechanisms have been relatively well elucidated, the mechanisms underlying emergence-namely the restoration of consciousness following anesthesia-remain incompletely understood. Emergence from anesthesia represents a critical stage of anesthetic management, with its efficiency and quality directly influencing postoperative recovery, patient safety, and the incidence of complications. Traditionally, anesthesia induction and emergence were considered to be symmetrical and passive processes, with emergence regarded as the reverse of induction that naturally occurs as anesthetic drug concentrations decline. However, recent advances in neuroscience suggest that anesthetic emergence is not merely a passive reversal but rather an actively regulated, multidimensional neurophysiological process with modulatory potential, and it is not entirely symmetrical to induction. Studies have demonstrated that neuronal activity in the cortex, activation patterns of brain regions, and neurotransmitter regulation during emergence differ substantially from those observed during induction. Key regulatory pathways implicated in this process include orexinergic neurons and the locus coeruleus-noradrenergic system. These findings provide a theoretical foundation for strategies aimed at facilitating emergence from general anesthesia.

Evidence further indicates that the sequence of functional recovery across different brain regions is heterogeneous during emergence. Clinical observations suggest that auditory perception is among the earliest sensory modalities to recover during anesthetic emergence. This phenomenon is of notable clinical significance, as it underlies the longstanding use of auditory interventions-such as calling a patient's name or giving verbal commands-in the operating room. Compared with other sensory modalities such as vision or nociception, auditory pathways regain responsiveness earlier. Although the precise neural mechanisms remain unclear, they are likely related to the auditory system, language processing circuits, and higher-order cortical integration of language. Recent advances in neuroimaging techniques, including electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), provide further support for this perspective. For example, a previous study demonstrated via intracranial recordings that during propofol anesthesia, the core auditory cortex continued to generate early auditory evoked potentials and frequency-following responses to 50 Hz sound stimuli, indicating preserved early cortical responses. Similarly, another study showed that following loss of consciousness, the primary auditory cortex retained rapid responses to auditory input, whereas higher-order cortical responses were markedly attenuated. These findings suggest that auditory cortices can respond to external auditory stimuli even in the early stages of emergence when anesthetic concentrations remain pharmacologically significant, thereby supporting the use of auditory stimulation in facilitating recovery. Moreover, recent studies have investigated how specific linguistic content (e.g., a patient's own name) and acoustic characteristics (e.g., familiar voices) influence emergence quality. One study found that calling a patient's name elicited stronger responses and facilitated awakening more effectively than generic verbal cues. Similarly, another research reported that playback of maternal voice recordings shortened extubation time and reduced the incidence of emergence delirium in pediatric patients.

In addition to auditory stimulation, non-verbal somatosensory interventions are also commonly applied in clinical practice to promote emergence. Nevertheless, research on the role of such non-verbal stimulation in emergence from general anesthesia remains limited. Previous research demonstrated that acupuncture at acupoints such as Renzhong and Yongquan could accelerate the recovery of consciousness after general anesthesia. However, standardized protocols and robust evidence supporting the use of mechanical somatosensory stimulation to facilitate emergence are currently lacking. And its specific stimulation methods, intensity, timing of intervention, and safety parameters remain unclear.

Animal studies demonstrated in that electrical stimulation of glutamatergic neurons in the brainstem parabrachial nucleus can induce recovery of the righting reflex and behavioral arousal in mice under sustained isoflurane anesthesia, accompanied by a marked reduction in electroencephalographic δ waves. Subsequent studies further confirmed that stimulating glutamatergic neurons in the parabrachial nucleus accelerated anesthetic emergence, underscoring the critical role of this brainstem pathway in arousal regulation. The parabrachial nucleus is an important node in the central arousal network; its activation drives norepinephrine and dopamine release from the hypothalamus and brainstem, thereby enhancing cortical arousal. These findings suggest that peripheral somatosensory stimulation may ascend via spinal pathways to brainstem structures, thereby activating ascending arousal centers and accelerating recovery of consciousness. This provides a neurobiological basis for the use of peripheral somatosensory or spinal stimulation as non-invasive awakening strategies; however, clinical trials systematically validating such interventions remain lacking.

Although numerous studies have explored pharmacologic and non-pharmacologic approaches to accelerate emergence from general anesthesia, there is a paucity of randomized controlled trials evaluating the effectiveness and safety of non-verbal somatosensory stimulation. This approach is simple to implement, has a favorable safety profile, and does not increase healthcare costs. Its effects on emergence efficiency, emergence quality, and postoperative complications (e.g., delayed emergence, agitation) warrant systematic investigation, and such findings would provide evidence for clinical guidelines on anesthetic emergence.

Furthermore, electroencephalography (EEG), as a non-invasive method for real-time monitoring of brain function, is widely applied in assessing anesthetic depth and recovery of consciousness. Studies have shown that during emergence from general anesthesia, EEG exhibits characteristic changes, such as a reduction in high-amplitude slow waves, reappearance of α oscillations, and a gradual increase in β activity. Incorporating EEG frequency dynamics into the study design may help elucidate the neural mechanisms by which stimulation interventions modulate the arousal process, offering more direct neurophysiological evidence to optimize both monitoring and intervention strategies during anesthetic emergence.

In summary, the investigators propose to conduct a prospective, randomized controlled clinical trial to systematically investigate, in patients undergoing laparoscopic abdominal surgery under combined intravenous and inhalational general anesthesia, the effects of non-verbal somatosensory stimulation, either alone or in combination with verbal stimulation, compared with the conventional approach of verbal name-calling. Outcomes of interest include postoperative emergence time, quality, and safety. This study aims to provide robust scientific evidence to inform optimized intervention strategies for anesthetic emergence.