**4.2 Rapid sequence induction and intubation**

To minimize the risk of aspiration, rapid sequence induction and intubation (RSI) has become the standard induction technique in obstetric general anesthesia [2, 60–62]. The goal of RSI is to minimize the length of time between loss of consciousness and the establishment of optimal intubating condition. In the traditional RSI technique, after achieving ideal patient position, preoxygenation, and application of cricoid pressure, the administration of an intravenous induction agent is then rapidly followed by administration of an intravenous neuromuscular blocking agent; the trachea is intubated without attempts at positive-pressure ventilation (PPV) [3, 60]. The goal of avoiding PPV is to prevent gastric insufflation, as this may increase the risk of regurgitation [63]. However, OAA/DAS recommends considering the use of facemask ventilation, as the risk of regurgitation is low with correct application of cricoid pressure. Therefore, the steps in performing RSI in obstetric patient are: (1) proper patient positioning; (2) preoxygenation; (3) application of cricoid pressure; (4) administration of induction agent and neuromuscular blocking agent; (5) face mask ventilation; (6) tracheal intubation [49].

In obstetric procedures, propofol is the typical induction agent, barring hemodynamic or respiratory concerns. After the administration of induction agent, neuromuscular blocking drugs (NMDs) are then administered intravenously to facilitate optimal intubating condition. Succinylcholine or suxamethonium has historically been the most commonly used NMD for RSI in obstetric patients because of its rapid onset and short duration, allowing resumption of spontaneous ventilation in the event of failed intubation [2, 3, 64]. The optimal dose of succinylcholine is 1–1.5 mg/ kg [3, 65–67]. Although the level of plasma pseudocholinesterase decreases during pregnancy, studies show that the duration of action of succinylcholine in pregnant women remains unchanged [68]. Since the advent of sugammadex, a fast-acting reversal agent specifically for rocuronium or vecuronium, nondepolarizing NMDs (e.g., rocuronium, vecuronium) can also be used in RSI technique as the alternative to succinylcholine [64, 69, 70]. The optimal dose of rocuronium is 1–1.2 mg/kg, and vecuronium is 0.3 mg/kg [71–75]. Sugammadex (16 mg/kg) can rapidly reverse the effects of rocuronium or vecuronium to prevent the prolong duration of action. Therefore, it can achieve the same clinical effects as succinylcholine without risk of hyperkalemia, bradycardia, myalgia, increased intragastric pressure, and increased intracranial pressure [71–76].

In contrast to standard RSI, modified RSI with low-pressure ventilation (<12 cm H20) with correct application of cricoid pressure, is recommended in RSI for obstetric patients. Ventilation is carried out using a facemask with a maximum inflation pressure of 20 cm H2O. The goal of PPV is to delay the onset of hypoxemia and increase the likelihood of successful facemask ventilation in the event of difficult or failed tracheal intubation [77, 78].

In pregnant women without risk of difficult airway, direct laryngoscopy using a Macintosh blade is preferred [2, 3, 79]. However, in patients at risk of difficult airway (e.g., obese) and those who fail tracheal intubation, practitioners should use a video laryngoscope to provide a better view of the glottis and thereby increase the chances of success [80–90]. Since all obstetric patients are at a higher risk for a difficult airway, video laryngoscope should always be available in all obstetric general anesthetics [49, 79]. If the view of the glottis is not optimal during the first laryngoscopy, the anesthesiologist may reduce or remove cricoid pressure and reposition the head and neck [91, 92]. Due to capillary engorgement and edema of the mucosal lining of the

airway in pregnant women, the risk for airway obstruction and bleeding during upper airway manipulation is higher than in the general population [13, 14]. Therefore, a small endotracheal tube (e.g., size 6.5 or 7.0) is recommended to minimize the risk of trauma and increase the success rate in pregnant women. To minimize the risk of pulmonary aspiration, a cuffed endotracheal tube is used. In addition, endotracheal tube introducer (e.g., flexible stylet, bougie) can be used to improve the success rate of tracheal intubation [2, 49].
