The Technique Of Rapid Sequence Intubation
aAmong the various clinical skills regarding the airway management both in and out of the operating room (OR), safe and effective rapid sequence intubation (RSI), when appropriate, is undeniably one of the most valuable and widely used techniques (Kovacs & Sowers, 2018). In a multicenter longitudinal study of almost 9,000 ED intubations, Walls et al. reported that RSI was the method of choice in 69% of the intubations and in 84% of all cases that required any intubation medication (Walls, Brown III, Bair, Pallin, & Investigators, 2011).
The existing literature regarding RSI, for the most part, refers to pre-hospital and emergency department (ED) induction. Yet, it can be exploited in diverse healthcare environments. A RSI is critical in many emergencies when the airway is at risk, and plays a key role in anesthesia during emergency surgical interventions. RSI is indicated in situations where the patient’s airway reflexes are preserved, since, in completely obtunded or arrested patients, the placement of an endotracheal tube (ETT) can be achieved without the use of medications (Ross & Ellard, 2016).
In clinical practice, RSI involves the quick administration of an induction and neuromuscular blocking agent in order to facilitate the ETT insertion in patients that cannot or are unwilling to cooperate, that are suspected of full stomach, are hemodynamically unstable or critically ill (Kovacs & Sowers, 2018; Stollings, Diedrich, Oyen, & Brown, 2014). The “rapid” part of the RSI regards the delivery of the induction medication and neuromuscular blocker, and it by no means implies a hasty or rushed process. To date, studies have suggested that the use of RSI leads to high rates of successful intubation and low complication rates (Kim et al., 2012; Okubo et al., 2017; Walls et al., 2011).
Nevertheless, their conclusions are likely limited, as most of them lack control groups, have small sample size, do not take into consideration possible confounding factors, and their findings cannot be generalized (e.g., studies in the OP, the pre-hospital or ED setting).The primary goals of RSI is to prevent hypoxia during the induction/intubation process, to shorten the time lag between induction and tracheal intubation in cases of unprotected airway by reflexes or by the cuffed endotracheal tube and to prevent pulmonary aspiration of gastric content (Stewart, Bhananker, & Ramaiah, 2014).
The first goal is routinely obtained by pre-oxygenation. This stage, typically, involves the administration of 100% oxygen for 3-5 minutes before induction of anesthesia, in order to prevent hypoxia under apnea. The second goal is achieved through a fast-acting hypnotic agent and a rapid-onset neuromuscular blocking agent in quick succession. Lastly, the risk of aspiration is decreased by the application of cricoid pressure (CP), by avoiding positive pressure ventilation until successful tracheal intubation, and by performing laryngoscopy and tracheal intubation only when the neuromuscular blockade is accomplished (Stewart et al., 2014).
Although RSI is a necessary skill in the airway management, unfortunately, there are no consistent guidelines or at least a uniform protocol determining each step of the procedure in situations where RSI is indicated. As a basis for discussion, an algorithm of RSI, known as ‘’classic RSI’’, comprising the following key steps has been proposed: preoxygenation, induction with thiopental and consequent administration of succinylcholine, application of CP, refraining from positive pressure ventilation, and, eventually, tracheal intubation with a cuffed tube before CP removal (Stept & Safar, 1970). We should stress that there is no evidence about the preventive effect of this practice against aspiration nor its contribution to improved outcomes. Yet, traditional RSI, although seldom used, is still considered a standard of care in the UK and many other countries.
National guidelines on RSI are established only in few European countries. Therefore, this “standardized” intervention may be differentiated by country (Wetsch & Hinkelbein, 2013). Even among anesthetists in the UK, the RSI technique that is followed varies (Sajayan, Wicker, Ungureanu, Mendonca, & Kimani, 2016). In fact, the ‘’traditional’’ method is now rarely performed. Perhaps, the use of RSI variations and the departure from the classical technique can be attributed to the recently-introduced methods of pre-oxygenation, newer medications, the recognition of the importance of the oxygenation during the apneic period and the unresolved controversy surrounding the use of CP.
The term ‘’modified RSI’’ is usually used for such variations. However, this term lacks a broadly accepted definition. In a study regarding the current management of RSI in Germany, there have been reported variations in pre-oxygenation, patient positioning and the administration of neuromuscular blockers, while almost 30% of the anesthetists did not perform CP (Rohsbach, Wirth, Lenz, & Priebe, 2013). A similar survey in the USA showed that most anesthetists proceeded to lung ventilation during the apneic period in a modified RSI (Ehrenfeld, Cassedy, Forbes, Mercaldo, & Sandberg, 2012).
There is no doubt that the existing data cannot provide clear and sound guidance on which situations a RSI is indicated, nor can determine the details of each stage of the procedure, in order to constitute ‘best practice’. In specific clinical cases, an anesthetist could choose not to administer thiopental, succinylcholine or to titrate the dose of induction agent. She/he could also choose to omit CP or to purposely assist ventilation prior to intubation. Thus, further research should be encouraged in order to shed light to the decision-making process. Given the pharmaceutical advances, chronic comorbidities, and higher risk profiles of our patients, the classical RSI has been adjusted to offer an optimum benefit-risk balance. This approach can be directed by updated contextualized practice guidelines.
Efficacious pre-oxygenation is an integral part of RSI. In a recent survey, the majority of anesthetists used either 3-minute tidal volume breathing or aimed for a FEO2 ≥0.9 (Sajayan et al., 2016). Another study demonstrated that eight vital capacity breaths in one minute improves the safety profile even in double the apneic time without hypoxia when compared to 3-minute tidal volume breathing (Rajan, Prasanth Mohan, & Cherian, 2015). As far as positive airway pressure is concerned, its application seems to result in increased duration of apneic period without hypoxia in all patients, including those with morbid obesity (Sreejit & Ramkumar, 2015).
Of note, despite the fact that less than half of anesthetists use continuous positive airway pressure (CPAP) in RSI, the majority of them (80%) use it exclusively for obese patients (Sajayan et al., 2016). This highlights the need to promote this simple and beneficial method in the airway training. Since 2001, when the previous national survey about anesthesia was conducted in UK, the medications used for RSI have changed significantly. Propofol is the most common drug used instead of thiopental (Sury, Palmer, Cook, Pandit, & Mahajan, 2014). This could be because propofol is equally effective and anesthetists are familiar with its use in the elective situations.
