All About RSI: A Primer
Introduction
Rapid sequence intubation protocol adoption is growing in EMS. While statistics on the number of adopting agencies are sparse, it has become a focal point of education in recent years. At the same time, academic and research interest in prehospital intubation is growing. Doing RSI well and training for success has never been more important.
Sedating and paralyzing someone, in effect taking their airway, is one of the most invasive procedures that clinicians can do. While it can have great clinical benefits and save lives, practitioners must also understand the gravity of their efforts and the potential risks it carries.
This article aims to provide EMS providers with a basic explanation of the most pertinent aspects of RSI and intubation in general. It is not intended to be an exhaustive discussion of every recent RSI development or the minute details of RSI; rather, the goal is to give any provider, new or veteran, an overview of the RSI process.
Definitions & Indications
Rapid sequence intubation, or rapid sequence induction, involves the consecutive administration of a sedative and paralytic to remove a patient’s protective airway reflexes and facilitate endotracheal intubation. Additional medications such as lidocaine and atropine can also be used to help blunt the body’s physiological responses to stress and avoid complications.
Classic indications include:
Severe head injury with loss of consciousness
Unconscious patients post-head injury have a high risk of aspiration, apnea, and hypoxia. In addition, these patients run the risk of seizure onset as ICP rises.
Respiratory failure
Patients who are obtunded, fatigued, or otherwise severely weakened secondary to respiratory distress should be considered for RSI.
A patient with a decreasing respiratory rate that was otherwise tachypneic and restless should make you consider RSI.
Shock states
Patients in any shock state can sometimes benefit from intubation. Patients who become severely obtunded or have declining respiratory status should be considered for RSI.
Airway burns
Patients with severe airway burns run the risk of laryngeal and upper airway edema worsening their respiratory status and eventually occluding their airway entirely. It is important to engage in proactive, aggressive airway management for these patients before they decline to the point of being unable to breathe at all and needing a surgical airway. We will discuss this more below.
The Biggest Decision - The Decision to Not
I want to address this early in this article; the biggest decision around RSI is the decision to not do it. RSI is an invasive, dangerous procedure that involves taking away a critical part of patient autonomy - their literal airway - and also comes with significant hemodynamic effects. RSI should not be frightening, but it should be practiced judiciously with respect for the gravity of it. The vast majority of critical patients that you come across in the field (or the ED) will not require RSI, even if they initially appear obtunded or in respiratory distress.
Do your best to exhaust every possible method of airway management before resorting to an RSI or intubation scenario. For instance, many obtunded patients who are unresponsive due to drugs or alcohol will respond well to manual airway positioning. We don’t want to be tubing every opioid overdose, do we? These same patients may appear critical (and often are) at first but are better suited to less invasive interventions with less overall risk. In addition, make sure that you resuscitate before you intubate (covered more in full below).
Understand the gravity of what you are doing, and understand that your role as an RSI provider in EMS helps pave the way for the rest of the field. RSI is a relatively new tool to the EMS world, and we must yield it responsibly if we’re going to continue to make advancements.
Anatomy Review
The airway is divided into two sections - the upper and lower airways.
The upper airway is composed of the oropharynx, nasopharynx, and hypopharynx. Running from top to bottom, the nasopharynx includes the nasal sinuses and runs down until it meets the oropharynx. The oropharynx is made up of the mouth itself and connects the hypopharynx with the nasopharynx. The hypopharynx is the lowest part of the upper airway and runs from the oropharynx down to the glottis.
The epiglottis is a flappy soft tissue structure that sits above the glottis. This is a critical structure to be familiar with and be able to locate during any airway procedure. It sits above the glottis and is withdrawn during breathing and at rest. It drops down onto the glottis and closes during swallowing to protect the lungs from aspiration. During laryngoscopy, this glottis is manipulated or lifted to allow for the vocal cords to be viewed. Intubations that do not allow for direct visualization of the vocal cords are more difficult and may require more intensive airway management.
View of the glottis. Not visible: The vocal cords are directly beyond the glottis, and should be visible during an intubation attempt.
The trachea is part of the lower airway and is a soft tissue tube that runs down into the bronchi and the lungs themselves. It is anterior to the esophagus and is normally guarded by the C-shaped cricoid cartilage. The vocal cords are attached to the wing-shaped arytenoid cartilage that sit around the trachea opening. These will serve as critical landmarks for intubation.
Ideal view of anatomic landmarks during laryngoscopy.
Procedure Details
Positioning - Do your best to prepare for successful intubation by focusing on early airway repositioning. Positioning of the patient allows for optimal views of the glottis and vocal cords during laryngoscopy. The traditional most optimal position is the sniffing position in which the patient’s head is tilted slightly back and the chin is extended slightly upwards. The midpoint of the ears should align with the sternal notch (Alvarado & Panakos, 2023). Use padding or blankets as needed to obtain this alignment. A hyper-angulated blade may be beneficial as it reduces the amount of ramping necessary to achieve a good view.
Clinical Pearls to Maximize Success
Maximizing first-pass success rates is paramount to avoiding adverse events and making your RSI go smoothly. We will cover the best practices to ensure success on the first attempt in this section.
Bougies are flexible, skinny plastic introducers that can be used to anchor an intubation attempt. The intubator is able to place the bougie into the airway and hold it in place to slide the endotracheal tube down into place. While there is no definitive evidence showing that bougies increase first-pass success rates, a meta-analysis found that it can be helpful in difficult airways and helps with success to the point that it should likely be part of first-line intubation attempts (Von Hellmann et al., 2023).
Image of a bougie curled for use. Endotracheal tubes can also be preloaded and slid over the bougie before placement into the airway.
Tidbit: Bougies can also be used as a form of secondary (albeit soft) confirmation. The cartilage lining of the cricoid is made up of several ring shapes. Dragging the tip of the bougie along the rings can produce palpable vibrations that would not be felt if the bougie was in the soft esophagus tissue.
SALAD is an acronym for suction-assisted laryngoscopy & airway decontamination (EMCrit, 2021). SALAD is a method used to maximize first-pass success rates and avoid hypoxia and aspiration. While video laryngoscopy is known to improve first-pass success and should be the first line in most instances, it can fail with gross airway contamination (Trent et al., 2021). It is especially relevant with massive pulmonary edema, gastric distention, and vomiting, or the case of a patient eating just before going down and requiring RSI.
Image sourced from Wikipedia.
SALAD begins by placing the suction catheter (preferably a DuCanto or other large-bore suction catheter) into the right side of the mouth (EMCrit, 2021). It can remain there passively to remove erupting contaminants from the esophagus/trachea or be moved by the intubator to target specific areas in the airway.
Preoxygenation is the practice of providing oxygenation in the time leading up to RSI/intubation proceeding to ‘buy time’ before the patient desaturates. You can achieve this with 3 minutes of 100 percent oxygen or approximately 8 full BVM ventilations with 100 percent O2 (Barbosa & Mosier, 2024).
Every RSI has an apneic period during which they receive less oxygen and are not ventilated as the tube is placed and secured; preoxygenating gives the patient oxygen reserves to survive this period. It is also important to use apneic oxygenation, commonly achieved by placing a nasal cannula at 15 LPM in the nose during airway attempts, to reduce desaturation during airway intervention (Barbosa & Mosier, 2024).
Crew dynamics are the last but perhaps the most critical best practice that we will mention. An RSI is an inherently stressful scenario - these patients are already critical, and we are making an active intervention to stop someone who is breathing independently. RSIs should be rehearsed and trained regularly, with each member of the team knowing their role before any actual airway interventions occur. RSIs should be slow and deliberate, not crash interventions, if possible. Always have a set specific leader with pre-defined roles amongst the crew members. If airway attempts are not successful, do not allow ego or pride to drive you to continue airway attempts - hand it off to another person, preferably the most experienced intubator.
Backup Methods & A Surgical Airway
As mentioned above, it’s important not to let your ego get in the way of your care. Knowing when to exhaust endotracheal intubation attempts and move to alternative methods is as important as RSI. It is critically important that we achieve an airway by any means possible when we RSI and endotracheal intubation is not the only means to do so.
Always have a backup method available when you decide to RSI. The most common backup is a “rescue” airway - a supraglottic airway. Supraglottic airways are airways that sit above the glottis and do not extend downwards into the trachea. They work by seating themselves around the trachea and at least partially occluding the esophagus. Common examples include the iGel and KING-LT supraglottics (pictured below). These are quick and easy ways to establish a secured airway but are not definitive. They are particularly not helpful in preventing aspiration or in the case of intratracheal damage such as airway burns that are becoming edematous. Ventilators will also require an endotracheal tube for long-term care.
Example of an iGel supraglottic airway device.
Surgical airways involve making an incision into the airway to establish a definitive airway - otherwise known as a cricothyrotomy. It is an emergency procedure that is to only be done in an emergent scenario where an airway is unable to be established. The common mantra for deciding on a surgical airway is that it should be performed in any can’t intubate, can’t ventilate scenario. Examples include:
Severe airway burns with edema to the upper airway
GSW patients with severe maxillofacial trauma and loss of anatomical landmarks (think shotgun or rifle wounds to the jaw)
Repeated blunt trauma victims
Severe anaphylaxis with progressed, obstructing airway edema/angioedema
Cricothyrotomy is a relatively simple procedure involving making an incision into the neck through the cricothyroid membrane. The cricothyroid membrane, as the name suggests, is a thin membrane located anteriorly on the neck between the cricoid and thyroid cartilages. It is palpable with one finger over the front of the neck. It is the thinnest section of the neck and allows direct access when cut to the trachea lumen for airway placement.
Locating the membrane involves finding the endpoint of the superior thyroid cartilage and the beginning point of the cricoid cartilage. It is a small depression felt in the junction of these two sections. Shifting the different cartilages from either side in a “laryngeal handshake” can help expose the cricothyroid membrane as the non-moving section (Drew & McCaul, 2018). Practice finding it on yourself, and assess for it in patients that you think may be heading for a difficult airway scenario. It is more difficult to find on patients with significant neck fat.
The basic steps of a cricothyrotomy procedure include:
Locating the membrane and then making a vertical incision running downwards.
This exposes the cartilage and soft tissue to allow for easier access.
A second, smaller horizontal incision is then made directly into the now-exposed cricothyroid membrane.
This allows for the introduction of a bougie and endotracheal tube.
Use suction and pressure to manage any bleeding present.
Insert a bougie into the open incision, sliding it downwards towards the torso.
Feeling the cricoid rings can be a good indicator of correct placement. Avoid placing the bougie into a false lumen in the subcutaneous tissue.
Slide the endotracheal tube over the bougie until the balloon is no longer visible.
Inflate the cuff once placed.
Follow regular airway confirmation procedures and ventilate the patient.
ETCO2 still works on a cric patient.
Image courtesy of EMCrit Project.
While surgical airways are, for most scenarios, an absolute last resort, it is important to be ready and willing to perform rapidly when needed. Surgical airways are a procedure that you should be intimately familiar with and train on regularly to build the muscle memory necessary for performing it under real stress conditions. Make every effort to avoid it, but also do not delay if it is needed. Being competent at RSI must go hand-in-hand with surgical airway competence.
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https://www.tecom.marines.mil/Portals/120/Docs/Student%20Materials/FMST%20Manual/CricothyroidotomyFMST1418.doc
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RSI Pharmacology Basics
There are three main categories of RSI medications: sedatives, induction agents, and additional agents. We will cover the basics of each class and the common examples below.
Paralytics, also known as neuromuscular blockers, are medications that are used to induce paralysis and allow for successful airway placement. There are two major classes: nondepolarizing and depolarizing paralytics. The term nondepolarizing versus depolarizing refers to their action on the neuromuscular junction; depolarizing polarizes and thus causes fasciculations while nondepolarizing merely block these junctions (Cook & Simons, 2023). They work on acetylcholine to either block acetylcholinesterase from reducing acetylcholine or blocking
Common paralytics include:
Succinylcholine (Depolarizing)
Depolarizing paralytic that works by blocking the action of acetylcholine on neuromuscular junctions (Hager & Burns, 2023)
Stops muscular movement
Causes fasciculations - watch for these to know when the drug has taken effect (Hager & Burns, 2023).
Major risk: hyperkalemia
Succinylcholine causes a transient rise in potassium levels that can cause clinical symptoms
Avoid with burn patients, chronic kidney disease patients, and those with crush injuries (Hager & Burns, 2023)
Malignant hyperthermia
Rare but life threatening complication involving excessive and unending stimulation of skeletal muscles resulting in hyperthermia and hyperkalemia (Hager & Burns, 2023b)
Hyperkalemia is secondary to rhabdomyolysis and acidosis
Usually the first sign is a sudden spike in ETCo2 readings followed by temperature rise (York, 2019)
Treatment
Prehospital: Active cooling, supportive care, maximize oxygenation
In-hospital: Large boluses of dantrolene sodium (York, 2019)
Sedatives are used in RSI to help blunt the patient’s stress response and avoid conscious paralysis. Remember: paralytics do not have any inherent anesthetic effect - these patients are fully awake if you only give a paralytic. Conscious paralysis is a horrific, traumatizing event that we must avoid at all costs. Always sedate before you paralyze.
Common sedatives include:
Midazolam (Versed)
A GABA agonist benzodiazepine that produces anterograde amnesia (in other words, high doses make patients not remember events and render them unconscious). Medication of choice for procedural sedation (Bounds & Patel, 2024).
Can be given via IV, IM, IN routes.
Usual duration of effects 60-120 minutes but can be shorter depending on patient profile (Prommer, 2020).
Etomidate
Short acting non-barbituate hypnotic that works as a GABA agonist. Useful for hemodynamic instability due to its minimal cardiovascular effects. (Williams et al., 2023).
Has NO analgesia properties (Williams et al., 2023).
Make sure to add analgesics. The process of RSI can be painful.
Avoid in the case of adrenal suppression (ex: Addison’s disease patients) (Williams et al., 2023).
This also applies to septic patients (Williams et al., 2023).
Propofol
Non-benzo, non-barbiturate anesthetic that works as a GABA agonist to produce profound sedation. Rapid onset with strong amnesia properties (Platnick & Chatterjee, 2023).
Not as common in prehospital realm
Major side effect: hypotension
16 percent of patients had SBP below 90 post-propofol (Platnick & Chatterjee, 2023).
Ensure adequate fluid resuscitation and vasopressors are available.
Requires constant infusion for prolonged sedation due to short duration of effects (Platnick & Chatterjee, 2023)
Wears off quickly, allowing neuro checks more often
Ketamine
Dissociative anesthetic medication that works as an analgesic at low doses and can induce unconsciousness at high doses
Resuscitate Before You Intubate
RSI medications are not without deleterious effects - we are both paralyzing the patient and taking away their respiratory drive with paralytics while suppressing the catecholamine response that was likely keeping them alive with sedatives and analgesics. We are taking away or at least suppressing the compensatory mechanisms that the body was previously using to try to stay alive. Therefore, ensuring that the patient’s body can sustain a drop in vitals before performing RSI is critically important.
A 2023 meta-analysis found that at least 1 in 3 patients - 33 percent - of hospitalized RSI patients experience at least some adverse event during their RSI. (Downing et al., 2023) Keep in mind that these statistics are for patients in the hospital with more resources at hand and often in less immediately emergent scenarios; prehospital statistics are likely even more worrisome.
The cornerstone of pre-RSI resuscitation is to get the patient to a point of relative hemodynamic stability with some buffer room for the damage you will be doing to their vitals. One way to do this is to calculate the patient’s shock index. Shock index is calculated by dividing the patient’s HR by their systolic BP = shock index (Behgam, 2020). A 2013 study found that a shock index over 0.9 is correlated with a higher risk of peri-intubation cardiac arrest (Heffner et al., 2013).
Therefore, support the vitals:
Correct hypovolemia as necessary with the use of crystalloids or blood products.
Providing blood products may eliminate the need for RSI in the first place. If we can correct a patient in hemorrhagic shock, we may not need to intervene with the airway.
Hypotension kills
Multiple robust studies have found pre-intubation hypotension to be the biggest risk factor for post-intubation cardiac arrest. (Rezaie, 2020)
Aim for the highest blood pressure obtainable before performing RSI.
We want wiggle room before we give medications that will inherently suppress hemodynamics. Paralytics, for one, can blunt vascular tone and drop blood pressure. They can undo the vasoconstriction patients need to stay alive. Sedatives, of course, can also cause vasodilation and reduce cardiac output. The body relies on catecholamines to stay alive - don’t take them all away without a buffer!
Use vasopressors and wide-open fluid boluses to obtain a solid blood pressure (Rezaie, 2020).
Push dose pressors such as push dose epinephrine offer an easy and controllable way to manage hypotension during RSI (Weingart, 2023).
Avoid RSI if hypoxic (even if that sounds counterintuitive).
Some desaturation is expected during RSI to start.
Aim for a saturation goal of at least 94 percent ideally before beginning RSI (Aguilar & Davis, 2012).
Make use of BLS adjuncts and other airway interventions as necessary
Obtain access early and aggressively
The more access available, the better. Patients experiencing RSI are likely to need multiple infusions in the future and will benefit from multiple access points.
References
Aguilar, S. A., & Davis, D. P. (2012). Latency of Pulse Oximetry Signal with Use of Digital Probes Associated with Inappropriate Extubation during Prehospital Rapid Sequence Intubation in Head Injury Patients: Case Examples. Journal of Emergency Medicine, 42(4), 424–428. https://doi.org/10.1016/j.jemermed.2011.06.127
Behgam, B. (2020, August 3). Resuscitate before you intubate – CriticalCareNow. https://criticalcarenow.com/resuscitate-before-you-intubate/
Bounds, C. G., & Patel, P. (2024, January 30). Benzodiazepines. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK470159/
Cook, D., & Simons, D. J. (2023, November 13). Neuromuscular blockade. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK538301/
Downing, J., Yardi, I., Ren, C., Cardona, S., Zahid, M., Tang, K., Bzhilyanskaya, V., Patel, P., Pourmand, A., & Tran, Q. K. (2023). Prevalence of peri-intubation major adverse events among critically ill patients: A systematic review and meta analysis. The American Journal of Emergency Medicine, 71, 200–216. https://doi.org/10.1016/j.ajem.2023.06.046
Drew, T., & McCaul, C. (2018). Laryngeal handshake technique in locating the cricothyroid membrane: a non-randomised comparative study. British Journal of Anaesthesia, 121(5), 1173–1178. https://doi.org/10.1016/j.bja.2018.07.034
Facep, R. M. L. M. (2015, June 8). Tips and tricks for performing cricothyrotomy - Page 3 of 3 - ACEP Now. ACEP Now. https://www.acepnow.com/article/tips-tricks-performing-cricothyrotomy/3/
Hager, H. H., & Burns, B. (2023a, February 20). Succinylcholine chloride. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK499984/
Hager, H. H., & Burns, B. (2023b, February 20). Succinylcholine chloride. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK499984/
Heffner, A. C., Swords, D. S., Neale, M. N., & Jones, A. E. (2013). Incidence and factors associated with cardiac arrest complicating emergency airway management. Resuscitation, 84(11), 1500–1504. https://doi.org/10.1016/j.resuscitation.2013.07.022
McKenna, P., Desai, N. M., Tariq, A., & Morley, E. J. (2023, February 4). Cricothyrotomy. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK537350/
Platnick, C., & Chatterjee, D. (2023, August 8). Propofol. OpenAnesthesia. https://www.openanesthesia.org/keywords/propofol/
Prommer, E. (2020). Midazolam: an essential palliative care drug. Palliative Care and Social Practice, 14. https://doi.org/10.1177/2632352419895527
Pulling the Trigger on the Surgical Airway with Dr. Chizmar. (2020, January 21). Apple Podcasts. https://podcasts.apple.com/gb/podcast/pulling-the-trigger-on-the-surgical-airway-with-dr-chizmar/id1498516253?i=1000465193997
Rezaie, S. (2020, April 13). Critical care updates: Resuscitation sequence intubation – hypotension kills (Part 1 of 3). REBEL EM - Emergency Medicine Blog. https://rebelem.com/critical-care-updates-resuscitation-sequence-intubation-hypotension-kills-part-1-of-3/
Weingart, S. W. M. (2023, August 28). EMCRIT 6 – Push-Dose pressors. EMCrit Project. https://emcrit.org/emcrit/bolus-dose-pressors/
Williams, L. M., Boyd, K. L., & Fitzgerald, B. M. (2023, June 26). Etomidate. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK535364/
York, B. C. (2019, January 18). Malignant hyperthermia: an overview. US Pharmacist. https://www.uspharmacist.com/article/malignant-hyperthermia-an-overview#:~:text=ABSTRACT%3A%20Malignant%20hyperthermia%20is%20a,succinylcholine%20(a%20muscle%20relaxant).
