Facilitated intubation, also known as medication-facilitated intubation (MFI) or sedation-facilitated intubation, refers to intubation performed using a sedative or anesthetic drug as an induction agent, without the use of a paralytic (neuromuscular blocking agent). In comparison, rapid sequence intubation (RSI) employs both an induction agent and a paralytic drug. Both procedures are performed to a varying degree by emergency medical service agencies across the nation.
Drug-facilitated intubation protocols, including regulations for both medication-facilitated intubation and rapid sequence intubation, vary between states and in many cases, between regional and local emergency medical service agencies. One recent study found that eighteen states (35.3%) have statewide drug-facilitated intubation protocols. Of those states, only one (5.6%) has a protocol for sedation-facilitated intubation. The remaining seventeen states (94.4%) with drug-facilitated intubation protocols use intubation with sedation and a neuromuscular blocking agent. Regional and local use of medication-facilitated intubation and rapid sequence intubation is harder to ascertain, as there are no published studies regarding the extent of the use of drug-facilitated intubation other than on a statewide level.
Utilization of medication-facilitated intubation compared to rapid sequence intubation also varies based on the need of the patient and safety of the procedure.
The patient should be evaluated for signs that intubation may be difficult: the presence of upper front teeth, history of difficult intubation, any Mallampati status different from 1 (2.55) or equal to 4, and mouth opening less than 4 cm. The likelihood for a difficult intubation increases continuously from 0 (when no risk factor is present) to 2, 4, 8 and 17%, when one, two, three and more than three factors are present.
The Mallampati score alone does not offer complete coverage in ascertaining the ease of intubation. The presence of vomitus or foreign bodies in the airway and surgical alterations can make intubating very difficult, even with a normal Mallampati score. The basic anatomy evaluation is also limited due to the ability, or lack thereof, of the patient to participate. If one is considering medication-facilitated intubation, the patient is already semi-comatose or in extremis and may not be able to follow directions. Direct visualization in the mouth along with external landmarks are needed to assess the risk/benefit ratio of attempting to intubate with medication-facilitated intubation versus rapid sequence intubation or to simply continue with non-invasive methods of ventilation.
A position statement on drug-assisted prehospital intubation published by the National Association of Emergency Medical Service Physicians (NAEMSP) refers specifically to sedation-facilitated intubation. The organization recommends that the same training, monitoring, and quality assurance standards be adopted by emergency medical service agencies performing sedation-facilitated intubation as those performing rapid sequence intubation. NAEMSP also notes that since the drugs used as induction agents are frequently used for other indications by emergency medical service (e.g., midazolam used to treat seizures), that training should emphasize providers’ understanding of the role of these agents in airway management.
Allergy to medications is the primary contraindication to use of medications to facilitate intubation. Other contraindications include disease states and conditions that may make some drugs typically used contraindicated.
NAEMSP also offers a consensus recommendation that benzodiazepines and opioids not be used as induction agents in sedation-facilitated intubation, as their safety profile is less than ideal. Etomidate is more promising but more studies are needed.
Typical equipment is used that would be needed for any airway management situation. Intravenous (IV) access to deliver sedation and, if part of the protocol, neuromuscular blockade, is critical, as are oral and nasal airways, a bag-valve mask (BVM), oxygen supply, suction, and an intubation kit, including various sizes of endotracheal tubes and Mac and Miller blades. The provider should anticipate complications while intubating and have extra materials on hand, for example, IV fluids for hypotension caused by some induction agents, and airway adjuncts such as laryngeal mask airways (LMA) or King tubes for patients who cannot be intubated.
Various descriptions of sedation-facilitated intubation performed by prehospital agencies in the United States cite the use of drugs such as etomidate, midazolam, and ketamine as induction agents.
Benzodiazepines such as midazolam are known to cause hypotension when used in dosages high enough to facilitate endotracheal intubation. Benzodiazepines also have a relatively slow onset and unpredictable efficacy in some patients.
Etomidate has a better profile as a possible induction agent for sedation-facilitated intubation. It has a favorable hemodynamic profile, it is not likely to cause hypotension, and it causes a more predictable sedative effect. Studies, however, do not show an increased intubation success rate with etomidate compared to midazolam. One study showed an equivalent success rate (83% for either agent alone, and 85% for the two used together), and another study found no real significant difference between the two agents (82% for etomidate and 75% for midazolam). Etomidate can cause myoclonus, but the effect of this on intubation success rates has not been studied.
Other induction agents have not been adequately examined for their use during sedation-facilitated intubation.
There is limited data regarding the success of sedation-facilitated intubation using these agents, but several studies do indicate an endotracheal intubation success rate which is less than ideal – 85% in one study and 67.5% in another. Success rates reported with rapid sequence intubation tend to be higher. One aeromedical study reported a very large difference, a success rate of only 25% when only etomidate was used, compared to 92% when the same dose of etomidate, plus succinylcholine (a neuromuscular blocking agent), was used. Several studies carried out by anesthesiologists in the operating room environment show similar results.
Rapid sequence intubation has been chosen over medication-facilitated intubation in the emergency department setting due to its lower risk of complications. One study carried out in a large urban emergency department showed a greater number and severity of complications when a neuromuscular blocking agent was not used; these complications included aspiration (15%), airway trauma (28%), and even death (3%). None of these complications were noted when rapid sequence intubation was utilized. The same study showed a lower rate of multiple intubation attempts, esophageal intubations, and cases where the provider was unable to intubate, for rapid sequence intubation compared to medication-facilitated intubation.
Rapid sequence intubation is the standard of care in most emergency department intubations. Both rapid sequence intubation and medication-facilitated intubation are carried out by emergency medical service agencies in the United States, and more studies are needed to determine if rapid sequence intubation should be the standard of care in the prehospital environment as well. As discussed, limited studies thus far indicate an improved intubation success rate when rapid sequence intubation is performed compared to medication-facilitated intubation for emergency airway management.