The Effectiveness Of Rapid Sequence Intubation In And Out Of The Operating Room
Among 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. 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.
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. An RSI is critical in many emergencies when the airway is at risk and plays a key role in anaesthesia 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. 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. 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. Nevertheless, their conclusions are likely limited, as most of them lack control groups, have a 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 are 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.
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 anaesthesia, 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.
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. 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. Even among anaesthetists in the UK, the RSI technique that is followed varies. 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 anaesthetists did not perform CP. A similar survey in the USA showed that most anaesthetists proceeded to lung ventilation during the apneic period in a modified RSI. There is no doubt that the existing data cannot provide clear and sound guidance on which situations an 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 anaesthetist could choose not to administer thiopental, succinylcholine, or to titrate the dose of the 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 on 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 anaesthetists used either 3-minute tidal volume breathing or aimed for a FEO2 ≥0. 9. Another study demonstrated that eight vital capacity breaths in one minute improve the safety profile even in double the apneic time without hypoxia when compared to 3-minute tidal volume breathing.
As far as positive airway pressure is concerned, its application seems to result in increased duration of the apneic period without hypoxia in all patients, including those with morbid obesity. Of note, despite the fact that less than half of anaesthetists use continuous positive airway pressure (CPAP) in RSI, the majority of them (80%) use it exclusively for obese patients. This highlights the need to emphasize and promote this simple and beneficial method in the airway training.
Since 2001, when the previous national survey about anaesthesia was conducted in the UK, the medications used for RSI have changed significantly. Propofol is the most common drug used instead of thiopental. This could be because propofol is equally effective and anaesthetists are familiar with its use in the elective situations. CP is considered a standard of care in many areas of the world, especially in the UK, North America, and Australia. However, it is not a standard practice elsewhere and maintains a controversial issue. Its performance seems to be in decline in Europe, and some pre-hospital organizations do not approve its use. CP may also not be common practice in regions where there are not skilled healthcare providers to assist the anaesthetist. In general, concerns in the implementation of CP include difficulties in laryngoscopy, lack of solid evidence of its effectiveness, potentially increased reflux risk and deterioration of unnoticed trauma in larynx or cervical spine. Moreover, concerns about the accurate cricoid force application, patient discomfort, and increased physical and cognitive workload on the part of the healthcare professionals make CP anything but a “simple maneuver that can be taught to an assistant in a few seconds, ” as once perceived. In recently released guidelines by various international societies, including the 2015 Guideline on Airway Management by the Board of the German Society of Anesthesiology and Intensive Care Medicine, and the 2015 European Resuscitation Council Guidelines for Resuscitation, the routinely use of CP is no longer recommended. It is clear that these guidelines reflect the skepticism of the corresponding medical societies regarding the safety and efficacy of this technique. This could have significant medicolegal implications since a physician could not anymore be accused of not having used CP. Based on results of non-RCT trials, a recent Cochrane systematic review concluded that CP may not be essential to perform RSI safely.
It is acknowledged that there are two schools of thought on the benefits of CP. It is true that there are no randomized controlled trials that prove the favorable results of CP in patient safety and efficacy, and the level of evidence to encourage the application of CP is poor. Due to ethical constraints, such trials are highly unlikely to gain approval. Even if such a study was conducted, it would not reveal much information because of practical issues. Thus, the efficiency of CP should be evaluated through other means. On the other hand, reports of the preventive role of CP in gastric insufflation make it difficult to safely argue against its efficacy. We recognize that the use of CP could impede some aspects of airway management, especially when it is poorly applied; however, any complications are reversible as soon as it is removed. One of the principal issues in assessing the overall efficiency of CP is to investigate whether CP successfully fulfills its primary goal of reducing the risk of gastric regurgitation and pulmonary aspiration. It is evident that CP cannot completely eliminate that risk. In a number of studies, regurgitation still occurred even with the application of CP. We cannot deny that, ideally, the regurgitation situations should be eliminated. Yet, it is not necessary such high expectations to be met in order to prove the efficacy of CP. As long as CP can be proved to result in decreased incidence of regurgitation without causing any complications, this approach may continue to be considered a beneficial maneuver.
Fundamentally, CP is a technique that completely occludes the hypopharyngeal lumen, thus impeding the passage of gastroesophageal content. The rationale behind CP has been verified by advanced imaging techniques. Eventually, this fact is one of the most cogent arguments supporting CP. The evident, tangible effect of the compression of the esophageal entrance provides substantial credibility to the procedure. At this point, critics and doubters might wonder why, then, there are so much evidence against effectiveness of CP and objections to its application. The answer could lie in the nature and history of CP research. Since its first publication in 1961 and not until the 21st century, a safe and widely-accepted CP protocol was lacking. For almost forty years, the efficacy of CP was under debate in absence, though, of a standardized procedure. In their attempt to build on previous literature, researchers usually used imprecise magnitude of cricoid force, followed invalid start/stop times, and applied CP on patients who nowadays would be unsuitable for this technique. Thus, early trials on CP should be dissected to warrant the accuracy of the conclusions.
If CP is to be used during RSI, the maneuver must be performed in a safe and standardized manner, minimizing the risk of harm. This goal could be best achieved by reviewing the various differentiations in CP protocols and creating uniform guidelines. In the past, physicians argued over many details of the procedure. Nevertheless, after years of research, there is a general agreement about some of the more critical points. Regarding the cricoid force, it is now commonly accepted that 10 N of CP should be used just before induction in conscious adult and adolescent patients. On loss of consciousness, the cricoid force should be raised to maximum 30 N and maintained until successful intubation. However, this is a general guidance that cannot address individual or situational issues. Therefore, the safe implementation of CP should also factor in the patient’s health conditions. Moreover, clinicians should not scruple to refrain from CP if it is suspected to hinder intubation. Finally, there is a large number of other issues that lack extensive research, like the proper CF for morbidly obese patients or the combination of CP with other anaesthetic procedures.
Yet, the establishment of a standard protocol for CP does not ensure per se the clinical safety and efficacy of the procedure. Good practice must be secured by the dissemination of knowledge to the relevant healthcare professionals through training programmes and ongoing education. The majority of the current instructions referring to CP have been available in the literature for more than a decade. Nevertheless, frontline physicians still apply CP with inconsistent, even inappropriate, modifications in the maneuver. As an example, concerning the timing of CP, it is established that light pressure should be applied before induction. A survey, however, showed that almost 50% of the healthcare providers waited to perform CP until the patient was completely unconscious. More worrying is that over 30% of the anaesthetists reported that they removed CP precipitously before the confirmation of successful intubation.
Correspondingly, theoretical knowledge concerning cricoid force has not always led to practical implementation among physicians. It has been well evidenced that a significant proportion of fully licensed and certified airway management providers are not aware of the appropriate amount of cricoid force. Even among those who know, many do not often calibrate their technique to make sure that the generated force is accurate. Such misapplications are not approved by existing protocols.
As it has been demonstrated, apart from the importance of an RSI consensus, the human factor plays an equally key role. RSI is not a one-man procedure, neither should it be treated as such. Teamwork contributes to success and nursing staff are an integral component of it. Among the stages of the process, an anaesthetist nurse is mostly involved in preparation, protection, positioning and post-intubation management.
The nurse is expected to check and have available the equipment for the intubation, including this for failed or difficult airway situations. To this end, the nursing staff should check and prepare the drugs and monitoring, and ensure the intravenous access, preferably by two lines. They should also prepare two functioning laryngoscopes, stylet, bougie, and a suction device, as well as test the cuff inflation of the ETT and have smaller sizes accessible. During the maneuver, CP is mainly applied by the nurse and it should not be released until instructed by the intubator otherwise. In case of suspected cervical spine injury, the anaesthetic nurse could be called on to perform in-line stabilization. Moreover, in a failed intubation, the assistant’s priority is the sufficient patient’s oxygenation, as well as to predict the subsequent steps and to provide the operator with the necessary equipment. Finally, as soon as ETT placement is confirmed, the tube is tied or taped in place. At this point, blood pressure is measured and reported to the team leader, and mechanical ventilation is initiated.
As it can be assumed, the most active and vital contribution of the nursing staff in the RSI regards the drug preparation and administration and the CP application. And, although drug errors, including mislabelling, syringe swaps, failure to mix drugs, are recognized as serious but rare contributors to RSI complications, the most alarming evidence regard the CP implementation by the nurses. In a recent study, the nursing assistants could poorly state correctly (9. 3%) and apply (20. 9%) the appropriate pressure. This substandard level of knowledge is also reported in several other studies whereby only 1. 3-17. 8% of the perioperative nurses correctly stated the required amount of CP. Another study showed that anaesthetic nurses are not aware of the correct cricoid anatomy and pressure as well as the ability to apply correct force. Among staff members, though, the highest overall knowledge level about the technique, although still inadequate, is reported in perioperative nurses. Given those facts, it is hardly surprising that 52% of anaesthetists check whether their assistants are trained in applying CP. Checking of competency to apply CP is essential when an RSI is performed outside an operating theatre, or when a new provider is assisting with RSI. A missaplication could not only lead to increased chance of regurgitation and pulmonary aspiration, but could also impede laryngoscopy. Correct application of CP can be taught with an in-service, hands-on training that includes information about the anatomy of the area, the appropriate amount of force, and the right timing for the initiation and release of pressure. It is reported that, after training, nurses substantially increase their knowledge and feel more confident as airway assistants. However, although such training of providers performing CP seems reasonable, since it would have to be provided for a great number of healthcare professionals every 2 weeks to 3 months, it might not be feasible.
RSI remains an important component of induction of anaesthesia under certain circumstances. The development of new medications and the revalidation of the existing ones may improve the efficacy and ensure the safety of RSI. Regarding CP, we have not yet reached a point where we can give a definite answer as to whether or not the potential benefits of CP outweigh the potential risks such that CP could constitute a mainstream practice. Nevertheless, is this question even approachable? Perhaps. Yet, as the medical profile of the patient becomes more complex, protocols and algorithms can never entirely replace an actively engaged healthcare professional, and must rather be considered a guide for best practice.
