Abstract: Objective To explore the optimal dosage of intravenous lidocaine in monitored anesthesia care (MAC) for percutaneous endoscopic lumbar discectomy (PELD). 
Methods Patients undergoing PELD in MAC from September 1, 2024 to February 1, 2025 in Hebei General Hospital were randomly divided into three groups: low-dose group (0.5 mg/kg, L group), medium-dose group (1.0 mg/kg, M group) and high-dose group (1.5 mg/kg, H group). Lidocaine loading doses of 0.5 mg/kg, 1.0 mg/kg and 1.5 mg/kg were administered intravenously within 20 min before the initiation of the surgery, and then maintained at a dose of 1.5 mg·kg-1·h-1 until the end of the surgery. The narcotrend index (NTI), Ramsay score, modified observational assessment of alertness and sedation score (MOAA/S score), visual analogue scale (VAS) score before administration (T1), at the initiation of surgery (T2), at 0.5 h after the initiation of surgery (T3), at 1 h after the initiation of surgery (T4) and at the end of surgery (T5) were recorded. The data of electrocardiogram signal were collected during surgery, and heart rate variability was calculated after surgery. 
Results At T5, the L group showed a significantly lower NTI compared with the H group, suggesting significant differences (P＜0.05). No significant effects were observed in interaction between time points and time points between groups (P＞0.05). The VAS scores in all three groups exhibited a rise-then-fall trend over time, with significant difference in interaction between time points (P＜0.05), but no significant difference was found in interaction between groups and time points between groups (P＞0.05). At T2, the L group exhibited significantly shorter average normal-to-normal interval duration (AVNN) than both the M group and the H group (P＜0.05), and maintained this significant difference compared with the H group at T5 (P＜0.05). No significant difference was found in interaction between time points and time points between groups (both P＞0.05). Over time, both the high-frequency and low-frequency peaks in the L group showed an initial increase followed by a decrease. At T2, the high-frequency and low-frequency peaks in the L group were significantly higher than those in the M group and the H group. The significant difference was found in interaction between time points and time points between groups (P＜0.05). The incidence of intraoperative hypertension (30% higher than the mean arterial pressure at T1) in the L group was higher than that in the H group, and the difference was statistically significant (P＜0.05). 
Conclusion Preoperative intravenous infusion of lidocaine at a loading dose of 1.5 mg/kg and an intraoperative maintenance dose of 1.5 mg·kg-1·h-1 for PELD in MAC can effectively alleviate intraoperative pain and maintain the patient's conscious and calm state to cooperate with the operator, which is safe and effective.  

Key words: diskectomy, endoscopy, anesthesia, lidocaine