Continuing Education Activity

Facilitated intubation, also known as medication- or sedation-assisted intubation, involves using a sedative or anesthetic induction agent during intubation without a paralytic agent (neuromuscular blocking agent). In contrast, rapid sequence intubation uses both an induction and a paralytic agent. Intubation with a sedative medication alone requires an awareness of the difference in physiological and anatomical responses that may occur in the absence of a paralytic agent, such as laryngospasm and increased intracranial pressure due to the stimulation of the laryngeal reflex. Understanding the nuances of facilitated intubation is crucial, especially in the prehospital setting, where the availability of paralytics is service-dependent, and in many cases, paralytics may not be available, particularly in ground emergency medical services (EMS). This activity reviews the indications, contraindications, complications, and techniques for intubation without a paralytic agent, emphasizing the vital role EMS providers play in the chain of survival of critically ill patients. 

Objectives:

• Assess the criteria for evaluating the need for intubation.

• Identify the indications for intubation without paralytic agents.

• Compare the different available induction agents for medication-assisted intubation and rapid sequence induction intubation. 

• Communicate the importance of effective care coordination among the interprofessional team to improve outcomes for patients requiring intubation without paralytics.

Introduction

Facilitated intubation, also known as medication- or sedation-assisted intubation, refers to using a sedative or anesthetic to decrease consciousness, muscle tone, and protective airway reflexes to improve visualization during laryngoscopy. In contrast, rapid sequence intubation uses both an anesthetic and a paralytic agent to quickly induce decreased mental status, complete muscle paralysis, and apnea, aiming to create optimal intubating conditions. Emergency medical services (EMS) agencies perform both medication-assisted intubation and rapid sequence intubation throughout the United States and Europe.

Geographic Variation

Drug-assisted intubation protocols, including regulations for both sedation-assisted intubation and rapid sequence induction, vary between states and, in many cases, between regional and local EMS agencies. Although rapid sequence intubation and medication-assisted intubation are included in the paramedic's national scope of practice, each state, region, and local EMS agency establishes airway management protocols that may vary significantly.

A study found that 18 states (35.3%) have statewide drug-assisted intubation protocols. Of these, only 1 state (5.6%) has a protocol for sedation-assisted intubation,[1] with the remaining 17 states (94.4%) using rapid sequence intubation. Regional and local rates of medication-assisted intubation and rapid sequence intubation are difficult to ascertain, as there are no published studies or surveys at the local level.

Anatomy and Physiology

A key component of drug-assisted intubation is the identification of a potentially difficult airway. Before induction, the patient should be assessed for signs indicating that intubation may be challenging:

• The presence of upper front teeth
• History of difficult intubation
• Mallampati status difference from class 1 (2.55) to class 4

The likelihood of difficult intubation increases with the number of risk factors present.

• No risk factor is present = 0%
• 1 risk factor present = 2%
• 2 risk factors present = 4%
• 3 risk factors present = 8%
• More than 3 risk factors present = 17%

The Mallampati score alone is insufficient to determine the ease of intubation and requires the patient to follow basic commands. The presence of vomitus or foreign bodies in the airway and surgical alterations complicate intubation, even with a normal Mallampati score. Basic anatomy evaluation may be limited if the patient cannot participate in the assessment due to altered mental status or unresponsiveness. If medication-assisted intubation is being considered, the patient is typically semi-comatose (or in extremis) and often unable to follow directions. In this situation, direct visualization in the mouth and external landmark assessment such as interincisor, hyoid-to-mental, and thyroid-to-hyoid distance (3-3-2 rule) can help identify a potentially difficult airway. [2][3]

Indications

A position statement on drug-assisted prehospital intubation published by the National Association of Emergency Medical Service Physicians (NAEMSP) refers specifically to sedation-assisted intubation. The organization recommends that EMS agencies performing sedation-assisted intubation adopt the same training, monitoring, and quality assurance standards as those performing rapid sequence intubation. The NAEMSP also states that since the drugs used as induction agents are often used by EMS for other indications—such as midazolam for treating seizures—training should focus on ensuring that healthcare providers understand the role of these agents in airway management.[4][5]

The indications for medication-assisted intubation are comparable to those for rapid sequence induction intubation. Typically, it involves a patient with decreased mental status—usually with a GCS less than 8—without a readily reversible cause, a patient with poor or absent respiratory effort, or a concern for impending airway compromise, such as a burn or traumatic injury. In hospitals where paralytics are available, some clinicians opt for medication-assisted intubation while performing laryngoscopy or intubation out of concern for a difficult airway. This strategy preserves a component of the patient's muscle tone and respiratory effort, allowing for prolonged laryngoscopy—whether direct, video, fiber optic, or nasopharyngeal—before desaturation occurs.

Contraindications

A primary contraindication to using a specific medication to facilitate intubation is an allergy to the medicines used. Secondary contraindications include disease states or conditions that may make some medication contraindicated or intubation itself relatively contraindicated, such as:

• Profound metabolic acidosis
• Neuromuscular diseases
• Hyperkalemia (specifically depolarizing paralytic agents)

In the prehospital setting, the most significant relative contraindication for medication-assisted intubation is the delayed time to definitive care and the risk of incorrectly placing an endotracheal tube in an uncontrolled environment.

Equipment

The equipment required for advanced airway management in the prehospital setting is similar to that used in hospitals or emergency departments. Essential equipment includes:

• Patent and adequate intravenous (IV) access for medication administration
• Oral and nasal airways
• Ambu bag and face mask for ventilation and oxygenation before and after intubation
• Oxygen supply
• Suction equipment
• Intubation kit, including various sizes of endotracheal tubes and Mac and Miller blades

Peri- and post-intubation monitoring devices, including continuous pulse oximeter, continuous electrocardiography, and waveform capnography, should also be used to ensure patient tolerance of the procedure and confirm successful intubation. Healthcare providers should anticipate complications before the intubation procedure and have extra materials present to manage anticipated complications. One common complication is post-intubation hypotension, which requires IV fluids and vasopressors. Another common cause of post-intubation hypotension is the failure to predict the effect of the patient's rate of respiration pre-intubation, whether there is respiratory compensation for metabolic acidosis, and setting the ventilatory rate too low. The result of a low ventilatory rate in this situation is the potentiation of metabolic acidosis, which can negatively affect cardiac function and cardiac contractility and decrease vascular tone. 

If the advanced airway is unobtainable, healthcare providers should be prepared with rescue options such as a supraglottic or a surgical airway.

Personnel

In the pre-hospital setting, one or more paramedics often perform medication-assisted intubation. Some protocols require a second paramedic for assistance, whereas others allow for a solo provider. Depending on the EMS system and the nature of the call, additional personnel such as EMTs, firefighters, pre-hospital nurses, or EMS physicians may assist in treating critically ill or injured patients. In many parts of the United States, the healthcare providers performing medication-assisted intubation or rapid sequence intubation most frequently include air medical personnel staffed by flight nurses, flight paramedics, or clinicians.

Preparation

Once the appropriate patient is selected, the healthcare provider must ensure it is safe to proceed with medication-assisted intubation. The necessary intubation equipment, including primary and backup devices, should be checked for functionality before the procedure and kept readily available. Most importantly, the healthcare provider should be prepared to implement a well-practiced difficult airway algorithm in case of visualization challenges or an unsuccessful first intubation attempt.

If possible, sufficient time should be spent on pre-oxygenation of the patient to facilitate denitrogenation and prolong safe apnea time for the procedure. The patient's heart rate, blood pressure, and pulse oximetry should be continuously monitored. Before administering the induction agent, the healthcare provider should ensure the patient's blood pressure is adequate to tolerate the anticipated peri-intubation decrease in blood pressure. IV fluids and vasopressors should be readily available if the patient becomes hemodynamically unstable.

Technique or Treatment

Induction Agents

The most commonly used induction agents in the United States include etomidate, midazolam, and ketamine, depending on statewide and EMS agency-specific protocols. 

Benzodiazepines such as midazolam can cause hypotension when administered in doses high enough to facilitate endotracheal intubation. Benzodiazepines also have a relatively slow time of onset and can have an unpredictable level of sedative effect, depending on the population.[6] Even though EMS providers may be comfortable with midazolam, its adverse effect profile precludes it from being a primary agent in medication-assisted intubation. 

Etomidate and ketamine are considered better choices as an induction agent for medication-assisted intubation.[7] Etomidate has a favorable hemodynamic profile and a predictable sedative effect. Although both etomidate and ketamine have unique induction properties and adverse effect profiles, the superior agent has not been well-established, leading to many studies. One meta-analysis concluded that etomidate causes less post-induction hypotension without impacting first success pass rate or mortality. [8] Conversely, Koroki et al suggest that when compared to etomidate, ketamine may decrease mortality when intubating the critically ill patient. [9] 

Current NAEMSP guidelines recommend against the use of midazolam and advocate for either etomidate or ketamine as induction agents.

Complications

Limited data exist regarding the success of sedation-assisted intubation using current induction agents. Two studies show different endotracheal intubation success rates that are less than ideal, 85% and 67.5%.[10][11]  Success intubation rates reported with rapid sequence intubation tend to be higher than medication-assisted intubation. A study conducted in an aeromedical setting reported a significant difference between rapid sequence intubation and medication-assisted intubation success rates. In this study, the success rate when etomidate was used alone was only 25%, compared to a 92% success rate when the same dose of etomidate was combined with the paralytic agent succinylcholine.[12] Studies conducted by anesthesiology in the operating room setting show similar results.

Rapid sequence induction has been chosen over medication-assisted intubation in the emergency department setting due to its lower risk of complications.[13] A study conducted in a large urban emergency department found that the absence of a neuromuscular blocking agent was associated with a higher incidence and severity of complications, including aspiration (15%), airway trauma (28%), and even death (3%).[14] The risk of these complications was much reduced when rapid sequence intubation was performed instead of medication-assisted intubation. The same study showed a lower rate of intubation attempts, esophageal intubations, and cases of intubation failure when the healthcare provider used rapid sequence intubation.

Clinical Significance

EMS agencies in the United States perform both rapid sequence induction and medication-assisted intubation in accordance with their statewide and local EMS service protocols. When comparing rapid sequence intubation and medication-assisted intubation, some experts advocate for the use of rapid sequence intubation when available rather than medication-assisted intubation.[15] However, further EMS-specific studies are needed to determine which technique is the safest and most effective.

Rapid sequence intubation is the standard of care in most emergency departments, whereas medication-assisted intubation, in any form, is infrequent in the hospital setting.

Enhancing Healthcare Team Outcomes

Intubation is performed in many different settings. More resources are available to ensure success when intubation is performed in a controlled environment, such as the operating room, intensive care unit, or emergency department. In contrast, the prehospital setting is an uncontrolled and variable environment where this intubation may have to be performed with or without access to paralytic medications and minimal backup resources. To optimize patient outcomes and increase the chance of successful intubation in the prehospital setting, selecting the appropriate patient, identifying potential difficult airways early, and performing the procedure without harming the patient or delaying transport to definitive care are essential. Clinical judgment is also required; in some cases, the patient should only have basic airway maneuvers and bag-valve-mask ventilation performed while being transported rapidly to the nearest emergency department. Avoiding failed intubation is critical, as it is associated with high morbidity and mortality.