EMS Facilitated Intubation Without Paralytics

Anatomy and Physiology

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 of difficult intubation increases continuously from 0 (when no risk factor is present) to 2, 4, 8, and 17% when 1, 2, 3, and more than 3 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 patient's ability, or lack thereof, 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 and external landmarks are needed to assess the risk/benefit ratio of attempting to intubate with medication-facilitated intubation versus rapid sequence intubation or simply continuing with non-invasive ventilation methods.

Indications

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 (eg, midazolam used to treat seizures), training should emphasize providers’ understanding of the role of these agents in airway management.[2][3][4]

Contraindications

The primary contraindication to using medications to facilitate intubation is allergy to medications. Other contraindications include disease states and conditions that may make some drugs 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.

Equipment

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.

Technique or Treatment

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 can 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.[5]

Etomidate has a better profile as a possible induction agent for sedation-facilitated intubation[6]. It has a favorable hemodynamic profile; it is not likely to cause hypotension, causing 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 2 used together). Another study found no significant difference between the 2 agents (82% for etomidate and 75% for midazolam.[7] 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.

Complications

There is limited data regarding the success of sedation-facilitated intubation using these agents. Still, several studies indicate an endotracheal intubation success rate of less than ideal – 85% in 1 study and 67.5% in another.[8][9] 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.[10] Several studies conducted 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.[11] 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%).[12] 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 could not intubate for rapid sequence intubation compared to medication-facilitated intubation.

Clinical Significance

Rapid sequence intubation is the standard of care in most emergency department intubations. Emergency medical service agencies in the United States carry out both rapid sequence intubation and medication-facilitated intubation. More studies are needed to determine if rapid sequence intubation should also be the standard of care in the prehospital environment. As discussed, limited studies thus far indicate an improved success rate when rapid sequence intubation is performed compared to medication-facilitated intubation for emergency airway management.

Enhancing Healthcare Team Outcomes

Intubation is usually performed in controlled settings like the operating room and ICU. However, in the field, it may be performed by EMS, nurse anesthetists, and surgeons without access to paralytic drugs. The key is to perform the procedure without harming the patient. Clinical judgment is required; in some cases, the patient should be bagged and transported quickly to the nearest ED. Failed intubations are associated with high morbidity and mortality.