Airway control is a critical skill for the prehospital healthcare provider. The prehospital provider must be skilled in various methods of airway support ranging from simple airway positioning to the establishment of a definitive airway with an endotracheal tube. Drug-assisted intubation (DAI) is a term used for any use of medications to facilitate endotracheal intubation (ETI), with or without neuromuscular blocking agents. ETI with the use of neuromuscular blockade is known as rapid-sequence intubation (RSI). ETI without the use of neuromuscular blockade is known as sedation-facilitated or medication-facilitated ETI. RSI is the most common type of prehospital DAI performed. Some studies indicate that RSI is more successful than intubation with sedation alone both in the prehospital setting and the emergency department. The use of DAI by emergency medical services (EMS) systems varies throughout the United States. In general, ETI refers to the placement of an endotracheal tube orally. Although nasotracheal intubation is possible, it has largely fallen out of favor in the urgent care setting. In brief, indications for emergency ETI include:
Airway and ventilatory control in patients with intact airway reflexes. Situations in which DAI may be indicated include respiratory distress, decreased level of consciousness, intoxication, traumatic injury, and noncompliance with noninvasive ventilation attempts. Having DAI available in these situations could be life-saving. All of the indications for ETI in the emergency department are relevant to the prehospital setting. For non-arrest patients, drug-facilitated intubation and RSI have been associated with increased ETI success rates.
Addition of a critical life-saving tool to the prehospital provider’s armamentarium. Many prehospital providers already perform ETI as part of their scope of practice. DAI can be seen as an expansion of skills that paramedics and other advanced prehospital providers already possess. Paramedics with more extensive training and experience have been shown to have higher DAI success rates. In general, aeromedical EMS providers have been shown to have higher success rates with DAI. Although the need for DAI is infrequent in most EMS systems, having it available to adequately skilled and trained providers can save lives.
DAI provides the most optimal intubating conditions. A 2003 study by Wang et al. identified five factors associated with ETI failure: trismus, inability to pass the tube through the cords, inability to visualize the cords, presence of gag reflex, and increased weight. Except for increased weight, DAI can potentially resolve or improve all of these factors.
There is a lack of evidence showing a mortality benefit. The majority of research on outcomes and mortality has been in trauma patients. The bulk of the literature has shown an association between prehospital RSI and poor outcomes, particularly in head-injured patients. However, a 2010 randomized controlled trial by Bernard et al. did demonstrate more favorable neurological outcomes compared to patients intubated once they got to the hospital.
There is a risk of the inability to ventilate after sedation and paralysis. It is possible that the prehospital provider will be unable to place an endotracheal tube and unable to ventilate the patient with a rescue device or bag-valve mask. This is a worst case scenario which can potentially lead to worse outcomes than the patient would have had without DAI. Having a plan for failed airways is critical.
On-scene DAI delays transport to the hospital which can be detrimental, especially in trauma patients. The San Diego Paramedic RSI Trial noted that DAI added approximately 15 minutes of on-scene time.
Unfamiliarity or infrequent use of DAI medications may lead to dosing or administration errors. However, this risk could be minimized by frequent practice and the use of checklists.
There are adverse effects of pharmacological agents used for DAI. Many of the medications used for sedation and paralysis have unique side effects which can complicate or worsen a patient’s clinical status. The main adverse effect of sedatives used for DAI is hypotension, for which propofol and benzodiazepines are the most notorious. The National Association of EMS Physicians currently recommends against the use of benzodiazepines and opioids to facilitate ETI. Some studies indicate that etomidate administration can lead to adrenal suppression, but this is of questionable clinical significance. Succinylcholine is associated with an increased serum potassium concentration, which can be detrimental or life-threatening in certain situations. Ketamine is associated with increased salivation, laryngospasm, and possibly increased intracranial pressure. Additionally, patients may suffer arrhythmias or cardiac arrest after administration of DAI medications.
The absolute number of patients requiring DAI will be small. It is questionable whether it is worth the required time and resources. The majority of patients who are intubated in the prehospital setting are cardiac arrest patients.
There are several pitfalls which are common to ETI in general but should be considered in the discussion of DAI. These include tube misplacement, failure to recognize tube misplacement, providers being out of practice or inadequately trained, interrupting or delaying other critical actions to intubate, hyperventilation, and peri-procedural and post-procedural hypoxia. Hypoxia and hyperventilation have been shown to be devastating, particularly in trauma patients.
The decision to incorporate drug-assisted intubation into any EMS system must be individualized based on the needs of the community and the resources available to the EMS organization. In addition to the above pros and cons, factors unique to each EMS system such as training, staffing, and transport times must be considered. Additionally, the pros and cons of DAI for each patient must be weighed carefully. Knowing when not to do something is just as important as being proficient at it. A policy statement by the American College of Emergency Physicians, American College of Surgeons Committee on Trauma, and the National Association of EMS Physicians advocates neither for nor against prehospital DAI. The statement acknowledges that prehospital airway management is extremely important, and that “the scope of prehospital care may include drug assisted intubation (DAI) to facilitate ETI,” if EMS systems have “a specific need for the procedure and possess adequate resources to develop and maintain a prehospital DAI protocol.” There are many pros and cons of DAI in the prehospital setting, both literature-based and theoretical. Overall, the preponderance of the literature has not shown an outcome or mortality benefit to prehospital DAI. Much of this data focuses on traumatic brain injury patients. More research is needed to specify in which clinical situations DAI will provide a benefit.