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Background Laryngeal mask airway(LMA) have been widely used in clinical practice. Irritation to the patient during the insertion of a laryngeal mask can cause hemodynamic fluctuations, which is particularly unsafe for geriatric patients. We used probit regression analysis to determine the median effective dose of sufentanil to inhibit the response to LMA insertion in geriatric patients. Methods A total of 90 patients were selected for the study using the following inclusion criteria: age ≥ 65 years old, ASA grade I–III, and scheduled to undergo intravenous general anesthesia with LMA insertion. Each patient received a dose of sufentanil for anesthesia induction in one of six levels: 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3 μg kg−1. LMA insertion was scored with a 3-point, 6-category scale, with scores ≥ 16 indicating effective LMA insertion, and < 16 indicating ineffective LMA insertion. Mean arterial blood pressure (MAP), heart rate (HR), and bispectral index (BIS) were recorded 1 min before induction (T1), 1 min after induction (T2), 1 min after LMA insertion (T3), and 5 min after LMA insertion (T4) in each group. In addition, the plasma norepinephrine (NE) levels and adverse reactions were measured at T2 and T3 in each dosage group. Results Probit regression analysis showed that the ED50 of sufentanil inhibiting the response to LMA insertion in geriatric patients was 0.18 μg kg−1 (95% CI: 0.16–0.21 μg kg−1), and the ED95 was 0.31 μg kg−1 (95% CI: 0.27–0.38 μg kg−1), and the probit(p) = -2.34 + 12.90 × ln(Dose)($$\chi^{2}$$ χ 2  = 0.725, p = 0.948). Among all the patients, the number of effective LMA insertions was 57 (group A), and the number of ineffective LMA insertions was 33 (group B). The MAP, HR, and NE in group B were significantly higher than in group A at T3. Conclusions Sufentanil can effectively inhibit the patient’s response to LMA insertion, with stable hemodynamics and small stress response. The ED50 and ED95 were 0.18 μg kg−1 (95% CI: 0.16–0.21 μg kg−1) and 0.31 μg kg−1(95% CI: 0.27–0.38 μg kg−1), respectively. Trial registration This study was registered in the Chinese Clinical Trial Registry (Registration number: ChiCTR2100051827) on October 6, 2021.

Dexmedetomidine can effectively decrease the incidences of emergence agitation (EA) in adult patients, but there are major side effects related to increased dose of dexmedetomidine. The purpose of this study was to determine the median effective dose of dexmedetomidine in the prevention of EA among geriatric patients undergoing major open surgery with general anesthesia. A total of 50 geriatric patients were enrolled in this study. Dexmedetomidine 0.5 μg·kg−1·h−1 continuous intravenous infusion was administered to the first patient. The next dose was increased or decreased by .05 depending on the response of the previous patient, according to the Dixon up-and-down method. An “effective” or “ineffective” response was determined based on the Riker sedation-agitation score (RSAS), we defined “effective” as RSAS<5, and “ineffective” as RSAS≥5. The ED50 of dexmedetomidine in prevention of EA was .30 μg·kg−1·h−1 (95% CI, .27–.33) and the predicted ED95 was .42 μg·kg−1·h−1 (95% CI, .38–.51). The incidence of bradycardia was significantly increased in the group without EA compared to the group with EA (57.1% vs 13.6%, P = .002). The ED50 of dexmedetomidine in prevention of EA was .30 μg·kg−1·h−1 (95% CI, .27–.33) and the predicted ED95 was .42 μg·kg−1·h−1 (95% CI, .38–.51). Bradycardia was the main complication.