Study design
This randomized controlled, parallel-group study was conducted at the First Affiliated Hospital of Anhui Medical University, Hefei, China, from August 2022 to August 2023, and adheres to the applicable Consolidated Standards of Reporting Trials (CONSORT) guidelines for conducting and reporting clinical trials. Ethical approval was obtained from the Ethics Committee (PJ2022-06-56). This study was registered at the Chinese Clinical Registry Center (No. ChiCTR2200062116, https://www.chictr.org.cn/bin/project/edit?pid=168097, principal investigator: Yuanhai Li, date of registration: July 23, 2022) before the commencement of the study. All participants provided written informed consent. We informed patients that the study would not pose significant risks, though some discomfort could occur, and they were free to stop the procedure or not answer specific questions at any time. Patients were also made aware of their right to withdraw at any point without any impact on their medical care. Additionally, they were informed about alternative treatment options, including the choice of standard general anesthesia, which would not affect their overall medical treatment. We ensured clear communication to alleviate concerns and assured patients that they could pause the study at any time.
Inclusion criteria were as follows: patients between the ages of 18 and 65 years, with American Society of Anesthesiologists (ASA) physical status classes I and II, Mallampati-Samsoon upper airway classes 1 and 2, and scheduled for elective surgery under general anesthesia. Exclusion criteria were as follows: patients with severe cardiovascular and cerebrovascular diseases, suspected difficulty in mask ventilation, severe respiratory diseases, a history of related drug allergy, coagulation dysfunctions, a history of mental illness, self-reported nervousness and anxiety, or a history of susceptibility to nausea were excluded from this study.
Randomization and masking
A random allocation sequence was generated by a researcher. An anesthesiologist who was not involved in the study placed the patients’ codes sequentially into sealed and opaque envelopes. A researcher who was not in charge of patient care opened each envelope at the time of randomization. Another anesthesiologist, who was not otherwise involved in patient care, prepared the study drugs. There was no visible difference (same color, transparency, and turbidity) between the syringes of nalbuphine, dexmedetomidine. The syringes were labeled “study drug” and hand-delivered to the anesthesia team by the clinical research nurse.
Conduct of the study
Patients were randomly assigned to one of three ADL methods. The Dex group received a total dose of dexmedetomidine (0.75 μg/kg) infused for 10 min. The Nal group received nalbuphine (0.15 mg/kg) infused over 10 min. The control group received 0.9% saline solution infused over 10 min. At the same time, all patients in the three groups received airway anesthesia using nebulized lidocaine administered via a nebulizer with 10 ml of 2% lidocaine for 15 min and an oxygen flow of 5 L/min.
Upon arrival in the operating room, all patients’ vital signs were continuously monitored and recorded. Patients were then treated with one of the three different drug administration methods described above. The study subjects underwent ADL five minutes after the intravenous infusion was completed, which was immediately after atomization inhalation was finished. The degree of glottis exposure was recorded by the same anesthesiologist The ADL procedures were performed by a single senior anesthesiologist with extensive clinical experience as an attending physician in anesthesia, in order to minimize variability and potential bias. This clinician used a UE visual laryngoscope, which is a direct non-flexible visual laryngoscope, to expose the glottis as much as possible. In addition, many indicators were recorded by another anesthesiologist, including tolerance, nausea, coughing, pain, and depth of sedation during laryngoscopy, and patient satisfaction after surgery. In the event of a loss of consciousness with poor oxygenation, emergency airway equipment, including a facemask and bag, a laryngeal mask airway, oral and nasopharyngeal airways, and a transtracheal jet ventilator, was immediately available. All procedures and assessments related to this study were completed prior to the surgery. After a brief period of rest, patients were transferred for the induction of general anesthesia and the subsequent surgical procedures.
General anesthesia was induced with midazolam (0.02 mg/kg, approximately), etomidate (0.3 mg/kg, approximately), sufentanil (0.4 ug/kg, approximately), and cisatracurium (0.2-0.4 mg/kg). Maintenance included propofol (4-6 mg/kg/h) and remifentanil (0.1-0.2 μg/kg/min), with cisatracurium administered every 40-60 min for muscle relaxation. Anesthetic depth was monitored using BIS, adjusting the propofol infusion to maintain a BIS value of 45-55. Remifentanil infusion was adjusted to maintain mean arterial pressure and heart rate within ± 20% of baseline. For postoperative pain, 0.2 μg/kg of sufentanil was given 30 min before surgery ended.
Assessment method
Tolerance assessment: patient tolerance was graded using a 5-point comfort score, with 5 indicating no reaction, 4 indicating slight grimacing, 3 indicating heavy grimacing, 2 indicating verbal objection, and 1 indicating defensive movement of the head or hands (Tsai et al. 2010).
Satisfaction assessment: patient satisfaction was assessed after ADL. The patients rated their ADL experience on a visual analogue scale of 0-10, with 0 representing ‘extremely dissatisfied’ and 10 representing ‘extremely satisfied (Hanna et al. 2017; Sindhvananda et al. 2004).
Depth of sedation assessment: following medication, the patient’s depth of sedation prior to laryngoscopy was graded using the Richmond Agitation-Sedation Scale (RASS), with 0 indicating alert and calm; − 1 indicating drowsy, not fully alert but having sustained awakening for more than 10 s with eye contact to voice; − 2 indicating light sedation, briefly awakens with eye contact to voice in less than 10 s; − 3 indicating moderate sedation with any movement but no eye contact to voice; − 4 indicating deep sedation with no response to voice but any movement in response to physical stimulation; and − 5 indicating unarousable with no response to voice or physical stimulation (Otani et al. 2024).
Laryngoscopic exposure grading score: ADL glottis exposure was graded using the Cormack-Lehane (C-L) grading method as 1 for a full view of the glottis, 2 for a partial view of the glottis or arytenoids (glottis was observed with gentle pressure on the larynx), 3 for the only epiglottis being visible, and 4 for neither the glottis nor the epiglottis being visible (Won et al. 2024).
Cough severity scale: the severity of the patient’s cough was graded as “no cough” (0 points), a mild cough (an intermittent cough of 1 to 3 sounds; 1 point), a moderate cough (an intermittent cough of 5 to 6 sounds; 2 points), and a severe cough (a more obvious cough of 7 to 8 sounds; 3 points).
Pain degree assessment: the visual analog pain scale (VAS) was used to grade patient pain, with 0 indicating “no pain” and 10 indicating “extreme pain.”
Nausea rating scale:Patients were provided with a standardized diary to record severity of nausea using an 11-point numerical rating scale (with 0 = “no nausea” and 10 = “worst nausea imaginable”) (Hyman et al. 2020). The nausea rating scale was assessed after ADL.
Statistical analysis
The sample size was estimated using PASS software, version 15. According to our preliminary experiment study, the tolerance scores for the control, Dex, and Nal groups were 2.1 ± 0.7, 2.7 ± 1, and 3.7 ± 1.5, respectively, with a sample size of 18 patients per group at a power of 80% and a two-tailed α-error of 5%. Given a 10% sample loss rate, the sample size of this study was increased to 20 patients in each group.
All data were collected using Excel software (Microsoft Corporation, USA) and analyzed using the Statistical Package for the Social Sciences, version 25.0 (IBM Corporation, USA). The Shapiro-Wilk test was used to determine the normality of the data distribution. When the test results indicated that the data were normally distributed, the data were described using the mean and standard deviation (mean ± SD) and analyzed using one-way analysis of variance (ANOVA) to compare groupwise differences in outcome parameters, such as age, body mass index (BMI), baseline mean arterial pressure (MAP), baseline heart rate (HR), and baseline peripheral oxygen saturation by pulse oximetry (SpO2). Continuous data with a nonparametric dispersion were described using the median and interquartile range (IQR) and analyzed using the Kruskal-Wallis test to compare the groupwise differences in C-L scores. Repeated measures ANOVA was used to compare groupwise differences in MAP, HR, and SpO2 at T0, T1, T2, and T3. For the tolerance, satisfaction, pain, nausea, coughing, and sedation scores, if the homogeneity of variance test was satisfied, one-way ANOVA was used for group comparisons, and the least significant difference test was used for pairwise comparisons. If the homogeneity of variance requirement was not met, the Welch test was used for group comparison, and the Games-Howell test was used for pairwise comparisons. The chi-square test was used to examine the relationship between qualitative variables and independent samples (ASA I/II). A P value less than 0.05 was considered statistically significant, except for pairwise between-group comparisons. For the multiple comparisons (each group versus each other group = 3 comparisons), a Bonferroni-corrected significance level of 0.05/3 = 0.017 was used.
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