General Anesthesia; Tracheal Intubation

Cesarean section under general anesthesia requires intubation (insertion of a tube through the mouth into the breathing pipe to support breathing during the surgery). A device called a video laryngoscope is used, which has a smooth, curved, or less curved component called 'a blade' that helps the doctor gently see the voice box and guide the breathing tube safely into place during anesthesia; it is not a sharp tool blade. There are two types of video laryngoscopes blades: a Macintosh- style blade with a gentle curve, approximately 90 degrees) and a hyperangulated blade (with a more pronounced curve). Although video laryngoscopes are safe and both types have been used for around 20 years, it is not known whether one type works better that the other in patients undergoing cesarean delivery under general anesthesia. Because general anesthesia is used in only a small proportion (about 5%) of all cesarean deliveries, research in this area is limited. The main purpose of the study is to assess if a study comparing these two types of blades in the obstetric population is feasible. This is also known as a feasibility study, which aims to test the study plan and determine whether enough participants will join a larger study and accept the study procedures. The results will be used as a guide for a larger study.

This randomized, double-blind, controlled clinical study will evaluate the effects of different dose combinations of intravenous metoprolol and sufentanil on cardiovascular responses during oral endotracheal intubation under general anesthesia. Endotracheal intubation may cause transient increases in heart rate and blood pressure due to sympathetic stimulation. This study aims to determine whether metoprolol, in combination with different doses of sufentanil, can improve hemodynamic stability during and after intubation. A total of 900 adult patients aged 18 to 65 years with American Society of Anesthesiologists physical status I or II who are scheduled for elective non-cardiac surgery under general anesthesia with endotracheal intubation will be enrolled. Participants will be randomly assigned to one of 30 groups according to the combination of metoprolol dose and sufentanil dose. Metoprolol doses include 0, 0.1, 0.2, 0.3, 0.4, and 0.5 mg/kg, and sufentanil doses include 0.1, 0.2, 0.3, 0.4, and 0.5 mcg/kg. All participants will receive standardized anesthetic induction and maintenance. Hemodynamic changes will be observed for 10 minutes after intubation. The main outcome is the success rate of hemodynamic stability within 0 to 10 minutes after intubation. Secondary outcomes include the incidence of hypotension, hypertension, bradycardia, and tachycardia.