Abstract. The aim of this study was to calculate the median effective concentration (EC 50 ) of remifentanil (Rem) for the inhibition of laryngoscope-induced cardiovascular responses, and to observe its effects on the cardiovascular system and stress system. The study included 20 patients, who underwent time-scheduled vocal cord polyp resection with monitoring of heart rate (HR), mean blood pressure (MBP) and auditory evoked potential (AEP)-based A-line ARX Index (AAI). The Rem concentration was initially 5 ng/ml in the first patient, and the concentration selected for each subsequent patient was calculated from the previous case on the basis of whether or not cardiovascular reactions occurred. The HR, MBP and AAI at baseline, after the induction of anesthesia, and before and after the insertion of a self-retaining laryngoscope were recorded, with a change >15% recorded as a positive cardiovascular response. The EC 50 sequential method was used to calculate the EC 50 of Rem for the inhibition of laryngoscope-induced responses. Cortisol, interleukin-6 and blood glucose levels before and after laryngoscope insertion were also measured. The target-controlled concentrations for the 20 patients were as follows: 2 cases at 5 ng/ml, 6 cases at 4.2 ng/ml, 6 cases at 3.5 ng/ml, 4 cases at 2.9 ng/ml and 2 cases at 2.4 ng/ml. The EC 50 of Rem for the inhibition of laryngoscope-induced responses was 3.5 ng/ml with a 95% confidence interval (CI) of 3.47-3.60 ng/ml. A reasonable dose for inhibiting laryngoscope-induced responses was within the range 2.9-4.2 ng/ml. In conclusion, Rem exhibited an EC 50 of 3.5 ng/ml for the inhibition of laryngoscope-induced cardiovascular responses, with a 95% CI of 3.47-3.60 ng/ml, and a reasonable dose for the inhibition of such responses was 2.9-4.2 ng/ml.

BackgroundIn recent years, video-assisted thoracic surgery (VATS) has become increasingly widespread. However, the implementation of VATS requires the assistance with lung isolation techniques. Spontaneous breathing with laryngeal masks is also increasingly used in VATS. However, evidence on the characteristics of intubated anesthesia is insufficient.ObjectiveThis study aimed to explore whether intubation-free anesthesia has more advantages than other intubation methods in the clinical setting.MethodsPatients with lung tumors who underwent VATS in our hospital between June 2022 and October 2022 were included in the study. Perioperative data of patients, including basic information, intraoperative hemodynamic changes, postoperative inflammatory indicators, and adverse reactions were obtained through the electronic medical record system. According to the protocol of airway management during anesthesia, participants were divided into the following groups: laryngeal mask with spontaneous breathing group (LMSB group), laryngeal mask combined with bronchial blocker group (LM + BB group), double-lumen tube group (DLT group), and tracheal tube combined with bronchial blocker group (TT + BB group). All data were analyzed using SPSS 25.0 software.ResultsAt baseline, patients in the LMSB and LM + BB groups had a lower body weight (P = 0.024). Systolic blood pressure (SBP), diastolic BP (DBP), and heart rate (HR) were significantly higher in the DLT group than in the non-intubated group during surgery (SBP: T1 P = 0.048, T4 P = 0.021, T5 P ≤ 0.001, T6 P ≤ 0.001, T7 P = 0.004; DBP: T5 P ≤ 0.001, T6 P ≤ 0.001, T7 P ≤ 0.001; HR: T1 P = 0.021, T6 P ≤ 0.001, T7 P = 0.007, T8 P ≤ 0.001). The input fluid (P = 0.009), urine output (P = 0.010), surgery duration (P = 0.035), and procalcitonin levels (P = 0.024) of the DLT group were also significantly higher than those of the other groups. The recovery duration of the LMSB group was significantly longer (P = 0.003) and the incidence of postoperative adverse reactions, mainly atelectasis, was higher (P = 0.012) than those of the other groups.ConclusionAlthough the intubation-free anesthesia has less stimulation during operation and less postoperative inflammatory response, it has obvious adverse reactions after operation, which may be not the best anesthesia scheme for radical resection of lung cancer in VATS.Clinical trial registrationhttps://www.chictr.org.cn/showproj.html?proj=182767, identifier ChiCTR2200066180.