Abstract:Objective To explore the effect of different doses of nalmefene pre-administration on vital sign and respiratory depression of patients during painless gastroenteroscopy under fentanyl combined with propofol anesthesia. Methods A total of 195 patients who underwent painless gastroenteroscopy in TaiZhou Fourth People's Hospital from August 2024 to December 2024 were randomly divided into three groups: physiological saline group (Group S, n=65), 0.1 μg/kg nalmefene group (Group N1, n=65), and 0.2 μg/kg nalmefene group (Group N2, n=65). Two min before induction, patients in Group N1 and Group N2 received an intravenous injection of 0.1 μg/kg and 0.2 μg/kg nalmefene respectively, while patients in Group S were given the same volume of physiological saline. All three groups adopted the anesthesia scheme of fentanyl combined with propofol for anesthesia induction and propofol for maintenance. The primary observation indicator was the incidence of respiratory depression during the examination. Secondary observation indicators included vital signs [respiratory rate (RR), saturation of peripheral oxygen (SpO₂), mean arterial pressure (MAP), and heart rate at pre-anesthesia (T0), when the endoscope entered the esophageal inlet (T1), and upon awakening (T2)], anesthesia indicators [time to awakening, time to discharge from the procedure room, propofol dosage], satisfaction, and adverse anesthesia reactions (body movement responses, jaw thrust intervention, and nausea and vomiting). Results The incidence of respiratory depression was 18.5% (12/65) in Group S, 6.2% (4/ 65) in Group N1, and 3.1% (2/65) in Group N2, with statistically significant differences among the three groups (χ²= 10.282, P=0.006). However, the difference between Group N1 and Group N2 was not statistically significant (P> 0.05). At T1, the RR, SpO₂, and MAP in Group N1 and Group N2 were higher than those in Group S, and the RR and heart rate in Group N2 were higher than those in Group N1, with statistically significant differences (P<0.05). The time to awakening and time to discharge from the procedure room in Group S were significantly longer than those in Group N1 and Group N2, with statistically significant differences (P<0.05). Group N1 and Group N2 were superior to Group S in terms of the incidence of jaw thrust intervention and anesthesiologist satisfaction, with statistically significant differences (P<0.05). Conclusion Pre-injection of both 0.1 μg/kg and 0.2 μg/kg nalmefene can stabilize patients' RR and reduce the incidence of respiratory depression, with the 0.2 μg/kg nalmefene pre-injection showing better efficacy.