Awake Tracheal Intubation in the Emergency Department

Abstract

Awake tracheal intubation is a valid and highly recommended option for any situation where significant anticipated difficult intubation is expected. Despite expert recommendations and available video assisted device it’s not a common practice and it still underuse because it seems as a very complex procedure. With a well-structured protocol, education and training, most health care personnel in the emergency department could perform it in a matter of minute, without delaying urgent care and maintaining a patent airway for adequate oxygenation.

1. Introduction

1.1 Awake tracheal intubation definition

Awake tracheal intubation (ATI) is define as a technique where the patient is intubated without the need of sedative or paralytic agent, but instead with the use of local anesthetics the airway is numb to maintain an adequate ventilation and oxygenation [1, 2].

1.2 History and evolution throughout time

First described by Sir William MacEwen, a Scottish surgeon, in 1880 of a patient suffering from obstruction of a tumor from the base of the tongue [3]. Soon after in 1881, ATI under topical anesthesia with cocaine, was first describe by Franz Kuhn, a German surgeon. Since then, orotracheal intubation trough the mouth as suffered several modifications, from external, digital palpation of the pharynx and upper tracheal structure to the visualization of the vocal cords by direct laryngoscopy [4, 5]. In 1967 a year before the introduction of fiberoptic bronchoscopy (FOB) in clinical practice by Kensuke Ikeda of Japan, an English anesthetist, Peter Murphy used it to aid in the nasal intubation of a patient with Still’s disease [6]. Since the 90’s ATI with FOB has been recognized as a standard of care by different airway society practice guideline for the management of difficult airway, reporting a success rate of 88 to 100% in anticipated difficult airway patients [7].

1.3 Indications and contraindications

It is the standard of care for the management of anticipated airway in many practice guidelines, and it is recommended anytime there is suspected difficult laryngoscopy or facemask ventilation [8]. But there are some specific pathologies that are common practice for patient requiring ATI in the emergency department and are not limited to morbid obesity with a body mass index (BMI) of 40 or higher, pathology of the head and neck (large tumor, angioedema, obstructive sleep apnea) and a history of difficult intubation in the past. The only valid contraindication is a patient not accepting the procedure or not able to cooperative because of nonresponsive or altered mental status.

1.4 Incidence and statistics (difficult intubation and awake tracheal intubation)

The incidence of ATI in the emergency department is low (0.4%) [9] and it is lower than the incidence of difficult laryngoscopy in trauma patient in the emergency (between 12 and 14%) [10]. Reports suggest lack of familiarity and experience are the most common reasons.

1.5 Implementation in the emergency room settings. Controversies and discussions

This cause underutilization in those emergency department where other techniques like rapid sequence intubation (RSI) are more common [11]. This in part because of a strong believe that patient will not accept the procedure if asked. A qualitative, descriptive study in Sweden demonstrate that most patient undergoing ATI when tailored information and breathing instruction are giving during the procedure would not hesitate to undergo awake intubation again in the future if needed. The information provided should not overwhelm the patient with details about technical issues, instead it should cover basic knowledge of a stepwise approach and anticipate expected event like the discomfort if the nasal route if selected or possible complication like bleeding and how can it be corrected [12].

1.6 Benefits of awake tracheal intubation

There are several benefits with ATI, mostly because it permit and secure a patent airway to avoid the risk of low blood oxygen (hypoxemia) or high blood carbon dioxide (hypercapnia) [11] or the risk of food aspiration in the bronchi because protective laryngeal reflexes are preserved [8], and also to avoid the risk associated with induction agent commonly use in RSI like low blood pressure (hypotension) and slow heart rate (bradycardia) that could impended hemodynamic stability and increase morbidity and mortality.

2. Preparation

2.1 Patient selection

Selecting the right patient for ATI is the most difficult part. There is no evidence that support any individual method developed specifically for ATI and overall difficult airway predictions methods are unreliable, making all intubations potentially difficult in the emergency room [2, 13]. Despite these steps back emergency doctor most perform in a timely manner an in-depth history, targeting past difficult airway problem and how there were managed, followed by a thorough examination of the airway.

2.2 Cognitive aids

The use of cognitive aid can accelerate this process and it is highly recommended by difficult airway international guidelines [2]. Checklist and visual maps can help on decision making in environment such as the emergency room, who needs a rapid response, team collaboration and assurance that those who participate have a specific set of tasks.

2.3 Clinical and physical evaluation

Sign and symptoms could help in the decision making when it comes to perform intubation in a conscious patient with neck tumor or mass [14]. Some of these could be and not limited to acute change in voice, history of difficult breathing (dyspnea), difficult swallowing (dysphagia) with or without salivation, dyspnea not tolerated when lying flat only in the seated position. A physical examination could reveal difficult airway parameter (e. g. a Mallampati scale III or IV), large front of neck mass or tracheal deviation by visualization or palpation.

2.4 Imaging analysis and labs test

In an environment like the emergency room imaging evaluation at the bedside could facilitate airway assessment and safe time without the need for transporting the patient to the MRI or CT scan room. Two techniques have demonstrated high sensitivity and specificity and can be used for decision making. These are ultrasound and transnasal endoscopy or nasopharyngoscopy [7, 15]. Ultrasound could help in the assessment of tracheal deviation or obstruction in the presence of large front of neck mass or tissue. Also, it has been used in the emergency room for visualization of the cricoid membrane for urgent cricoidectomy to maintain ventilation if needed [15].

Above (Table 1) we use several patient characteristics to help guide clinicians in the emergency room in decision making and patient selection in case of awake tracheal intubation if needed.

Table 1.

Cognitive aid for decision making for the selection of patient when considering awake tracheal intubation.

3. Equipment and materials

3.1 Video assisted devices

Fiberoptic intubation (FOI) has been the standard method for many years in the management of difficult airway and it is the mainstay in awake tracheal intubation, either nasally or orally [16]. The advancement of the technology as incorporated high quality video recording, increase the suction power and single use disposable devices which decrease the incidence of cross contamination, among others.

Videolaryngoscopy (VL) has gain in recent years more attention because it is more available, easier, and safer to use than FOI [8]. Familiarity has increased his use in non-operating room environment like the emergency area. The main limitations are with patient with limited mouth opening and large obstructive tumors that impairs visibility. The lack of a suction channel may cause difficulty in patient with increase secretion or blood making it impossible to visualize supraglottic structure. There is no evidence that show superiority over FOI [17].

Other devices like direct laryngoscopy and optical stylets have been used and evidence has not shown significant differences in time and success rate, therefore could also be considered as a valuable alternative [18]. One of the mayors causes in selecting one device over a another may be familiarity and availability [8, 17]. The use of cognitive aid like the table above (Table 1) could help in selecting the right equipment. For example, in cases where the risk is low the emergency physician could start with Videolaryngoscopy, direct laryngoscope or flexible stylet, when the difficulty increases, and the risk is high the main choice should be fully awake fiberoptic intubation in a seated position with a front of neck approach.

3.2 Setup/arrangement

Ergonomics study the interaction of the environment and its impact on performance and safety [2], when it comes to airway management in the emergency room, time constraints and lack of adequate space could make it challenging to meet adequate standard and performance. But still, we must maintain the same standard as in the operating room (sterile gloves and gown, facemask, and continuous vital sign monitoring) [7].

Several factors should be considered before starting the procedure and everyone who is participating should be notify, these include patient position (seated, semirecumbent or lying down), the route of tracheal intubation (oral or nasal), visualization device (FOI or VL) and type of tracheal tube (reinforce or standard) [2]. If intubation is in the seated position a front of neck approach is the optimal choice, with the operator and assistant facing the patient, video monitor, patient vital sign monitor must be separate and in an adequate visible site for continuous monitoring. If the patient could tolerate lying down or semirecumbent position the operating physician could stand at the head of the patient and the assistant, other health personnel, video monitor and vital sign monitor on the opposite side towards the patient extremities. This approach is helpful and can be perform by the assistant in case head tilt or sniffing position it’s needed because of obstruction from oversedation or increase secretion. We discussed before which video assisted device is adequate base on patient characteristics and underlying pathology (see above). Tracheal tube size is normally selected base on patient age group (pediatric, adults) and internal diameter (ID) but in patient with sign of important obstruction a smaller size or ID than needed should be selected. Comparison of reinforce tube versus standard polyvinylchloride (PVC) tube as shown that the first have superior outcome in terms of ease of tracheal intubation, railroading (advancing the tracheal tube over the flexible bronchoscope) and decreasing laryngeal impingement [2].

3.3 Medications

The three main objectives of premedication are: (1) Airway preparation, (2) Aspiration prophylaxis, (3) Anxiolysis and sedation. Airway preparation can be accomplished by application of antisialagogues, which are medication that decrease secretion in the mouth, pharynx, and bronchi, the most used are the antimuscarinic, and they also facilitate local anesthetics absorption allowing better absorption conditions. Commonly used clinical practice are atropine, glycopyrrolate and scopolamine. Table 2, summarize dosing regimen and principal characteristics of antimuscarinic drugs [13, 19].

Drug	Dosing	Onset	Tachycardia	Antisialagogue	Sedation
Atropine	0.4–0.6 mg IV or IM; 7 to 10 μg/kg IV	1 min (IV),; 15–20 min (IM)	++++	++	+; Delirium (elderly)
Glycopyrrolate	0.2–0.3 mg IV or IM; 7 to 10 μg/kg IV	1–2 min (IV), 20–30 min (IM)	+++	+++	—
Scopolamine	0.4 mg IV or IM	5–10 min (IV), 30–60 min (IM)	+	+++	+++

Table 2.

Summary of commonly used antimuscarinic drugs and they principal characteristics.

Abbreviation: IV, intravascular; IM, intramuscular; Min, minutes.

If planning on using the nasal route, risk of bleeding is high because of highly vascular nasal mucosa and nasopharynx. Therefore, must be prepared with vasoconstrictor nose spray such has Phenylephrine 0.5% and Oxymetazoline 0.05%, which are applied topically 15 min before the procedure [13, 19].

Airway preparation with local anesthetics is a crucial part and an essential skill that should be dominated by physicians in the emergency room. The most commonly use drugs are lidocaine (2%) and tetracaine (1%) solutions or prepared canned spray [20]. Local anesthetics can be applied via topical or nerve block techniques. Topical administration could be applied by several ways, direct application using solution-soaked sponge or gauze, spraying directly to the oropharynx, or nebulizing the entire airway mucosa.

At our institution we prefer a combine technique that include nebulize local anesthetic with lidocaine 5% for 15–20 min beforehand and “spray as you-go” via the Fiberoptic bronchoscope working channel once the supraglottic structures are visible then wait another 1–3 min before intubation. This technique could be use via nasal or oral route.

Nerve block is the fastest way to achieve adequate airway anesthesia if time is a concern and it need smaller volume of local anesthetic. Using ultrasound guided technique could accelerate even more the process and success rate but it is a technique that need to be learned and master before trying it in the emergency room. Description of this technique it is beyond the objective of this chapter and can be available in several books and publications.

The mayor risk of local anesthetic is systemic toxicity, and it could lead to cardiovascular or neurologic impairment that also could be affected in these patients. Some authors are limited the total dose to 9 mg • kg [8] but we recommend that dose should be kept between 3 and 5 mg • kg, especially in the critically ill but with stable conditions.

Gastric reflux is another mayor concern in these patients and can lead to bronchial aspiration and pneumonitis [19]. Medications like Histamine H2 blocker, Proton pump inhibitor and gastrointestinal tract (GI) pro-kinetics are commonly used. H2 receptor blocker routinely used are cimetidine 300 mg and ranitidine 50 mg and work by decreasing gastric acidity and volume, with a peak effect within 30–60 min [13, 19]. At our institution they have been stop used routinely because of side effect like gynecomastia (cimetidine) or risk of gastric cancer (ranitidine). Proton pump inhibitor such as omeprazole (40 mg iv) may have the same mechamism as H2 receptor blockers and has gain popularity and replace H2 receptor blocker at our institution, GI track pro-kinetics increase gastric emptying by increasing motility and can also increase lower esophageal sphincter tone, Metoclopramide 10 mg IV is the drug of choice, the risk of extrapyramidal syndrome has limited is use in Parkinson disease patients.

Sedation and hypnosis have become an essential part, same as local anesthetics in the preparation of awake tracheal intubation. Allowing a less traumatic experience for the patient by decreasing the level of stress also for the operator. Not all patients would tolerate some of the recommended medication, even with smaller doses, and could increase the incidence of undesirable side effects like bradycardia, hypoxia, dyspnea and cardiac or ventilatory failure. It’s important to select the right patient and start at the minimal required dose of the medication titrated to adequate condition based on clinical signs [19]. These drugs are divided in several groups base on their clinical effects, anxiolysis (decrease anxiety), hypnosis (causes sleep or sedation) and analgesia (inhibit pain), they can be use alone or in combination. For anxiolysis the drugs of choice are Benzodiazepines and are the most popular used one in the emergency room, sometime there are the only medications used in preparation of awake tracheal intubation. Midazolam 0.5–1 mg IV or 0.07–0.1 mg · kg IM [19] have a rapid onset of time and shorter duration of action if administered intravascularly. Diazepam and Lorazepam are other drugs commonly but have a slower onset time and longer duration of action. Hypnosis could be accomplished by intravenous medication like Propofol and alpha 2 agonist like Dexmedetomidine. Propofol is a GABAergic central hypnotic, mostly popular among anesthesiologist but less used in other areas like the emergency department. Starting at a low bolus 30–50 mg and repeatedly over a period of 3–5 min until clinical effect, when combine with local anesthetic and analgesics and topicalization, could set the patient in good intubating condition with out overdosing. This will depend on clinical status and it’s does not recommend if patient is unstable cardiopulmonary. Ketamine is another intravenous hypnotic and lately as gained popularity in emergency room awake intubation because of some advantages over Propofol. It causes hypnosis, but also increases blood pressure and heart rate by increasing blood catecholamines, it also has analgesics effects. Despite all these effects, caution should be taken when using this drug because of common side effect like increase intracranial pressure, increased salivation and bronchi reactivity leading to airway closure laryngospasm and bronchospasm [21]. Recommendations are to start with low dose boluses, 50 mg, titrated to clinical effects, also in combination of antisialagogues, more potent analgesics like opioids and bronchodilator like Salbutamol inhaled [2, 21]. We do not recommend infusion dose of Ketamine because of increased risk of mentioned side effects.

Alpha 2 agonist like Dexmedetomidine an imidazole compound as become the sedative/hypnotics of choice when performing an ATI outside the operating room in ambulatory seatings [8]. This because in a couple of minutes could cause adequate intubating conditions without compromising the respiratory system. It also has low analgesics effect, and in combination of other analgesics could potentiate this effect. Cautions should be taken because of reported severe bradycardia which has led to cardiac arrest. Recommended doses are an initial boluses 0.7–1 mcg · kg over a period of 10–15 min followed by a continuous infusion at a rate of 0.2–0.6 mcg · kg · h [8].

Opioids have been excellent adjuvant in controlling pain and anxiety during ATI, they principal mechanism is blocking opioid receptors in the central and peripheral nervous system [13]. Fentanyl and Remifentanyl are commonly used because of rapid onset and shorter duration of action. Remifentanyl it is metabolized by nonspecific plasma esterases, making it a good agent for continuous infusion during the procedure [19]. Recommended regimes vary, a dosing strategy could be as fallow a bolus of 0.5 μg/kg followed by an infusion of 0.1 μg/kg/min then gradually titrated by 0.025 to 0.05 μg/kg/min. The authors favor target control infusion using the Minto or Eleveld pharmacokinetics models, targeting a site effect concentration between of 0.15–0.25 ng/mL [19].

Combination of various drug is a common practice; at our institution we use a combination of Dexmedetomidine and ketamine. Finally, when selecting a drug always consider it’s benefit base on patient individual clinical situation and hemodynamics.

4. Step by step approach

Clinical practice guidelines are a set of expert’s recommendations and consensus often divided in related topics. They are not recipes and are subject to be accepted, modify, or rejected [22]. They must be adapted to local situation and available resources. Checklists are step-by-step approach that accelerate and facilitate repetitive processes, providing an outline for each participant.

The Difficult Airway Society guidelines for ATI are an excellent example [2], it provides an evidence-based summary of some of the relevant topics mentioned above in this chapter. It uses cognitive aid like visual aid infographic and pneumonic like the sTOP technique, which consist of several steps define by letters.

The first letter, the ´s´ mean sedation and can use any of the drugs mentioned earlier in the equipment and materials section of this chapter, it is written in lower case because it is an “optional” step and can be avoided or use at any time before the procedure.

The second letter ´ T ´ stand for Topicalization and it’s the process of applying local anesthetics to numb the airway mucosa and allow procedure with mild discomfort for the patient. Most of the time we assess effectiveness based on patient report of heaviness or numbness of the oropharynx, but guideline recommend introducing object like suction or aspirations oral cannula to adequate good topicalization before procedure.

The third letter ´O´ it’s an essential part and it’s stand for oxygenation; comparison has demonstrated that of high flow nasal oxygen (> 30 L · min) have more effectiveness based on low desaturation incidents and expert recommendations. Use of supplemental oxygen is highly recommended by expert around the world and should be continue through the process of ATI.

The last letter ´P´ stand for the procedure of introducing the endotracheal tube and it finish once confirmation is assessed by two steps; visualize above the carina and capnography [8].

5. Complications

A traumatic procedure with or without bleeding, multiple attempts and failure to intubate can increase anxiety for the patient and the operator. Popular recommendation is to stop and analyze what step is the most difficult one and what changes should be made before attempting another try. If difficulty is the procedure itself, then it is better to handle it to a more experienced clinician.

Remember that the more attempt, this my cause mucosal edema that can lead to more obstruction. Attempt should be limited to three and advancing to another technique or equipment should be considered, like the use of supraglottic device, like laryngeal mask airway (LMA) and surgical airway front of neck airway (FONA), to maintain adequate ventilation and oxygenation.

6. Postprocedural care

Once confirmation that the endotracheal tube is in the right place and appropriately secure to the face; preparation for transferring to another area should be planned before. Patient should be anesthetized or deepen the sedation level and the administration of muscle relaxant should not delay; except they are contraindicated. Hemodynamic should be stable and monitoring like oxygen saturation (O2 sat), electrocardiogram (EKG), capnography and non-invasive blood pressure (NIBP).

7. Conclusions

Successful ATI should not be attempted alone, success is based on teamwork, good communication and patient cooperation.

A stepwise approach may reduce the incidence of failure and can assist the operator in finding difficult step.

Complication can occur and all emergency physicians should be prepared; calling for help in advance and maintain surgical doctor close by in case awake tracheostomy is need.