Impact of Low-Dose Sufentanil on the Effective Sedative Dose of Ciprofol for BIS-Guided Induction in Elderly Patients: An Up-and-Down Sequential Allocation Trial

Qing Han¹Chun-ming Hu²Jun-li Zheng³Xiao-dong Huang⁴Pei Chen⁵Wei-long Wang⁶Jin Zhou⁷Si-ren Shi³Zhen-feng ZHOU^8*

• ¹Department of Anesthesiology, The first People's Hospital of Linping District, Hangzhou, Zhejiang, China;, Hangzhou, Zhejiang, China
• ²Department of Anesthesiology,Hangzhou Women's Hospital,Hangzhou,China, Hangzhou, China
• ³Department of Anesthesiology, The first People's Hospital of Linping District, Hangzhou, Zhejiang, China, Hangzhou, Zhejiang, China
• ⁴Department of Anesthesiology,Hangzhou Women’s Hospital, Hangzhou, Zhejiang, China, Hangzhou, Zhejiang, China
• ⁵Department of Anesthesiology,Hangzhou Women’s Hospital, Hangzhou, Zhejiang, China;, Hangzhou, Zhejiang, China
• ⁶The Fourth School of Clinical Medicin, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China;, Hangzhou, Zhejiang, China
• ⁷The Fourth School of Clinical Medicin, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China, Hangzhou, Zhejiang, China
• ⁸Department of Anesthesiology, Hangzhou Women’s Hospital, Hangzhou, China

Objective: This study aimed to evaluate the effect of a single low dose of sufentanil on the effective dose of ciprofol required to achieve a bispectral index (BIS) <60 during anesthesia induction in elderly patients. Methods: A total of 48 elderly patients were randomly assigned to either the sufentanil plus ciprofol group (S+C group) or the ciprofol alone group (C group). A sufentanil dose of 0.1 μg/kg was administered to the S+C group (diluted to 5 mL), while the C group was administered 5 mL of normal saline. Five minutes later, the initial administration for both groups was 0.3 mg/kg ciprofol. Subsequent doses were adjusted in increments or decrements of 0.05 mg/kg according to the response of the preceding patient within the same treatment group, following two independent, arm-specific up-and-down sequences conducted in parallel. Successful sedation was defined as achieving a BIS score of <60 within five minutes following ciprofol administration. ciprofol's effective doses (ED50/ED95) were derived through probit regression. Results: A total of 23 patients were enrolled in the S + C group and 25 in the C group. The estimated ED50 of ciprofol was 0.075 mg/kg (95% CI: 0.024–0.123 mg/kg) in the S + C group and 0.267 mg/kg (95% CI: 0.159–0.361 mg/kg) in the C group. The estimated ED95 values were 0.246 mg/kg (95% CI: 0.141–14.566 mg/kg) and 0.439 mg/kg (95% CI: 0.340–67.768 mg/kg), respectively. The Pearson goodness-of-fit test of group S+C and group C were P=0.965 and P=0.615 respectively. The incidence of adverse events, including hypotension(39% Vs 64%) and respiratory depression(17% Vs 16%), did not differ significantly between S+C group and C group. Conclusion: Under BIS monitoring, the estimated ED50 and ED95 of ciprofol for induction in elderly patients were 0.267 mg/kg and 0.439 mg/kg, respectively, without sufentanil, and 0.075 mg/kg and 0.246 mg/kg with 0.1 µg/kg sufentanil. The addition of a low dose of sufentanil reduced the ciprofol requirement for BIS-targeted induction by about 44-72% without increasing the incidence of hypotension or respiratory depression. This regimen provides an effective and well-tolerated strategy for anesthesia in elderly patients, particularly in day surgery and outpatient settings.