[Influence of anesthesia on auditory evoked response]

Area of Science:

• Neuroscience
• Anesthesiology
• Audiology

Context:

• Auditory evoked potentials (AEPs) like ABR and MLR are crucial for intraoperative monitoring.
• Various anesthetic techniques can influence AEPs, potentially confounding interpretation.
• Understanding these influences is vital for accurate neurophysiological assessment during surgery.

Purpose:

• To investigate the relationship between different anesthetic methods and the characteristics of auditory brainstem response (ABR) and auditory middle latency response (MLR).
• To determine the optimal anesthetic approach for intraoperative AEP monitoring, particularly for eighth nerve surgery.
• To assess the impact of body temperature on AEPs in clinical settings.

Summary:

• Auditory brainstem response (ABR) and auditory middle latency response (MLR) were recorded in 128 patients under diverse anesthetic conditions.
• Anesthesia was categorized into three types based on AEP effects: Type A (enflurane, halothane) affected both ABR and MLR; Type B (thiamylal, diazepam) affected only MLR; Type C (NLA, fentanyl, ketamine, etc.) affected neither.
• Neuroleptanesthesia (NLA) emerged as the most suitable method for intraoperative ABR and MLR monitoring. Decreased body temperature significantly impacted AEPs, necessitating consideration during monitoring of comatose patients.

Impact:

• Identifies neuroleptanesthesia (NLA) as the preferred anesthetic for intraoperative auditory evoked potential monitoring.
• Provides critical insights into how different anesthetic agents differentially affect auditory pathway function.
• Highlights the confounding effect of hypothermia on auditory evoked responses, crucial for interpreting data in critically ill patients.