Difficult Airway Management in Adult Coronavirus Disease 2019 Patients

Airway Management Barriers (Plexiglass box and Plastic Covers)

In addition to PPE availability and use,^[34,35] barrier methods have been developed to protect HCWs from contamination with biohazards and viral particle spread during AGPs. Protective shields and barrier-enclosure systems were approved by the US Food and Drug Administration (FDA) in May 2020 to be used in addition, not as alternatives to proper PPE to decrease the spread of viral particles associated with the care of COVID-19 patients.^[36] Concerns about safety performance prompted the FDA to revoke the permit in August 2020. Barrier enclosures without the possibility of additional negative pressure are no longer recommended.^[37]

The effectiveness of barriers in decreasing viral transmission to HCW during airway management remains unclear in part due to the lack of proper scrutiny and research. Transmission of SARS-CoV-2 viral particles can still occur with barrier use via aerosolized viral particle escape through the existent operative holes or when the box is removed.^[38,39] In addition, barriers deviate from standard practice, potentially worsening performance, and may increase the complexity and duration of the intubation process. They limit the use of airway management devices that require space and impair the use of a second pair of hands to assist during the procedure. During an emergency, when rescue airway procedures are required, barriers may prevent an effective response. Simulation experiences have demonstrated that aerosol boxes for intubation are associated with higher failure rates and prolonged intubation times.^[40] These limitations are concerning during the intubation of routine airways and extubation, and in case there is a difficult airway.^[41]

Recommendations:

1. Risk factors for the physiologically difficult airway should be weighed before formulating an intubation plan. In COVID-19 patients, these include hypovolemia from aggressive diuresis, chronic oxygen desaturation, pulmonary hypertension, myocardial dysfunction, and cardiovascular collapse.

2. If feasible, the intubation team for difficult airway management should consist of 4 providers: a provider experienced in advanced airway management techniques, a second assistant also familiar with airway management, a respiratory therapist, and a spotter (who remains outside the room).

3. Use PPE as described in COVID-19 airway management guidelines for nondifficult airways.

4. If available, we recommend the use of a PAPR device as the first line of PPE for emergent intubations.

5. A difficult airway cart, which remains outside the patient room, should include disposable equipment, when possible.

6. An intubating "box" or barrier device is not recommended for management of the difficult airway in the known or suspected COVID-19 patient.

Preintubation Oxygenation

COVID-19 patients with respiratory distress due to hypoxemia may require tracheal intubation and mechanical ventilation.^[42,43] Preoxygenation increases the time to oxygen desaturation after induction/relaxation and may reduce the likelihood of cardiorespiratory arrest due to severe hypoxemia. In the COVID-19 patient with the difficult airway, preoxygenation is critically important due to the high likelihood of hypoxemia and because the duration of difficult airway management may be longer than in a nondifficult airway.

Preoxygenation Before Induction. Preoxygenation in COVID-19 patients with a known or suspected difficult airway is similar to that in a COVID-19 patient without a suspected difficult airway. In both circumstances, an appropriate facemask with a tight seal and attached to a high-efficiency particulate absorbing filter (HEPA) filter provides optimal preoxygenation in a spontaneously breathing patient. The goal is to achieve an end-tidal O₂ (EtO ₂) level of 90% as measured by a gas analyzer or for 3 minutes if an analyzer is not available. In the physiologically difficult airway where cardiorespiratory arrest may be imminent, neither goal may be possible, and attempts to deliver oxygen should continue throughout the intubation process.

In patients with respiratory insufficiency due to COVID-19, HFNO or noninvasive positive pressure ventilation (NIPPV: continuous positive airway pressure [CPAP]/bilevel positive airway pressure [BIPAP]/inhalation positive airway pressure [IPAP]) is commonly used.^[44–46] These strategies do not preoxygenate as effectively as a well-sealed facemask.^{[4,32,47–54]} In addition, EtO ₂ cannot be measured with HFNO and the risk of aerosolization/contamination may be higher than when preoxygenation is delivered by facemask. Particularly for the difficult airway, facemask oxygenation if possible is likely to deliver better preoxygenation.

Oxygenation During the Period Between Muscle Relaxant Administration and Successful Intubation. During the apneic period between induction and successful intubation, patients may desaturate due to lack of ventilation.^[53] In patients with COVID-19, desaturation can be rapid and persistent. The optimal method to deliver oxygen during this period is unclear. Evidence supporting the efficacy of apneic oxygenation during intubation with either HFNO or low flow nasal oxygenation (5–15 L/min) is mixed.^[54–63] Additionally, apneic oxygenation may increase the risk of droplet aerosolization.^[17,46] In patients with COVID-19 and a difficult airway, in light of the limited efficacy of apneic oxygenation to prevent oxygen desaturation after induction/muscle relaxation, and potentially increased risk of aerosolization, when hypoxemia is present or imminent, we recommend BMV with a well-sealed face mask.^[1,64] If BMV results in a significant mask leak, an SGA could be inserted to improve seal and facilitate ventilation.^[65] A second-generation intubating SGA could also serve as a conduit for flexible scope-guided tracheal intubation. Apneic nasal oxygenation may be considered; however, if the nasal cannula is adversely affecting the BMV seal, it should be removed. HFNO should not be used in conjunction with BMV due to concern of gastric insufflation.^[66,67]

Recommendations:

Preoxygenation before induction:

1. Deliver FIO ₂ 1.0 using a well-sealed facemask with a HEPA filter.

2. Target EtO ₂ 90% if possible (when a gas analyzer is available).

3. HFNO/NIPPV may be considered as an alternative technique, but end-tidal gas analysis is not available, and it may increase aerosolization risk.

Oxygenation after induction:

1. When hypoxemic, perform BMV with a well-sealed facemask.

2. When BMV is ineffective or results in a significant leak, insert a SGA, preferably a second-generation intubating SGA, to facilitate ventilation.

3. Consider the application or continuation of apneic nasal oxygenation.

Pharmacology for Airway Management

Clinical characteristics of COVID-19 patients requiring intubation include hypoxemia, tachypnea, hypotension, tachycardia, pulmonary hypertension, and altered mental status.^[19] Acute kidney injury and hypercoagulability are also features of severe COVID-19 infection.^[6,7]

Thus, the presence of the previous risk factors in critically ill COVID-19 patients thus increases the risk of a physiologically difficult airway. Precautions for such patients have been published previously, with recommendations about choice of induction agent and use of lower doses to avoid exacerbating hemodynamic instability, and ready availability of vasopressor infusions and resuscitation tools.^[5,19] Muscle relaxants should be selected to provide optimal intubating conditions and may require redosing for repeated attempts or reversal to facilitate reestablishment of spontaneous breathing. Succinylcholine should be used with caution in COVID-19 patients who present with acute kidney injury, as they may have elevated potassium levels.^[6,7]

In combative or delirious patients who will not cooperate with awake intubation, the use of ketamine in small increments or dexmedetomidine may be considered because each is less likely to cause respiratory depression.^[5]

Recommendations:

1. Review patients for risk factors for physiological difficulty.

2. Consider lower doses of induction agents.

3. Ready availability of vasopressor infusions and resuscitation tools.

4. Succinylcholine should be used with caution.

Awake Tracheal Intubation

Awake tracheal intubation (ATI) is often used to manage the difficult airway patient when routine induction of anesthesia, with or without neuromuscular relaxation, may result in a cannot intubate–cannot ventilate situation or other complications. The decision to use ATI is based on an assessment that weighs the risk of routine induction of anesthesia against the likelihood of awake intubation success, the ability of the patient to cooperate with the procedure, and the consequences of this more prolonged intubation technique. In patients with COVID-19, the extended time needed to perform ATI may increase the risk of severe oxygen desaturation and cardiorespiratory arrest and prolong HCW exposure. Additionally, preparation of the patient for ATI, as well as inadequate airway analgesia during airway management, may be associated with cough and gag, which likely result in increased airway secretion aerosolization. These COVID-19–related patient and HCW risks can temper the decision to proceed with ATI.^[68,69]

Decision to Proceed With ATI

As noted earlier, few absolute indications exist for awake intubation. Importantly, any decisions regarding the approach to securing an airway must be made by the particular clinician tasked with caring for that patient and be based on variability in experience, availability of devices and skilled aid, and the context in which airway management will take place. When evaluating a patient at risk of having a difficult airway, 3 airway findings may trigger a decision to perform ATI: (1) tracheal intubation and facemask or SGA ventilation are not expected to be rapidly and efficiently achieved; (2) tracheal intubation is not expected to be rapidly and efficiently achieved and the patient is at significant risk of aspiration of gastric contents; (3) tracheal intubation is not expected to be rapidly and efficiently achieved and the patient may not tolerate the period of apnea that would accompany routine or complicated induction of hypnosis and airway control (Figure 1).

Because of the risk to both the patient and HCWs described earlier, alternatives to ATI may be considered. These options include consultation with a more experienced clinician, if available, whose risk assessment or assistance may allow routine management, or, in the case of medical consultation for airway management in an ICU setting, explore options for medical intervention that do not involve tracheal intubation.^[52] The need for tracheal intubation and the assessed need to use an ATI technique are independent. When the risk of ATI (to both the patient and HCW) is high, seeking an alternative to tracheal intubation may be warranted.

Specific Issues With ATI

A provider experienced in advanced airway management techniques should evaluate the patient and decide whether ATI is needed.

Options to provide supplemental oxygen during the procedure include use of respiratory masks that allow endoscope passage (eg, endoscopy mask; Figure 2), use of low or high flow nasal cannula, and use of bronchoscope adaptors (when using a SGA as a conduit). As noted previously, HFNO/NIPPO increases the risk of aerosolization and may increase the risk of disease transmission.

If needed, sedation should be administered judiciously. As the patient may be physiologically compromised, the clinician should use their clinical judgement during titration. The goal of sedative use should be to alleviate patient anxiety while maintaining adequate spontaneous ventilation and cooperation. Small amounts of opioids (eg, 25–50 μg fentanyl intravenous [IV]) may reduce coughing. Antisialogogues, such as glycopyrrolate, can be administered before ATI to facilitate topical blocks and decrease airway secretions.

Because the nasal cavity may have a high viral particle load, nasal tracheal intubation may increase the risk of disease transmission.^[70,71] However, if contextual conditions (eg, patient condition, operator experience, etc) favor this route, then nasal tracheal intubation is a viable alternative.

Topical anesthesia is needed for ATI and administration should be routine as per the practice of the operator. In difficult airway patients with COVID-19, procedures with a high risk of coughing such as transtracheal (translaryngeal) injection of local anesthetics should be avoided. Using techniques such as injecting local anesthetics into the larynx and trachea via a flexible bronchoscope or encouraging the patient to aspirate viscous or solutions of local anesthetic delivered to the hypopharynx can be used (eg, holding the patient's tongue with a gauze pad as a local anesthetic is trickled into the pharynx.)

Possible Intubation Techniques

Flexible Intubation Scope. If an FIS is used, then a remote screen (video image) should be used if possible as it moves the operator's face away from the patient's airway and reduces the chance of infectious exposure during coughing and other aerosolizing patient reactions. The gap between the outer diameter of the FIS and the inner diameter of the tracheal tube should be minimized to reduce the likelihood of difficulty passing the tracheal tube past the vocal cords and thus limit aerosol spread during intubation. Single-use FIS is preferable due to difficulties in cleaning reusable devices. Properly secured suction through the working channel is unlikely to increase infection risk. In contrast, oxygen insufflation may increase the likelihood of aerosolization. An endoscopy mask (Figure 2) may be used to enclose the patient's mouth and nose during the procedure.

Videolaryngoscope. If a videolaryngoscope is used for ATI, then a detached screen will allow the operator to move his/her face away from the path of coughing and other aerosolizing patient reactions.

Recommendations:

1. A provider experienced in advanced airway management techniques should determine and perform ATI if it is required.

2. Take steps to minimize aerosolization during airway topicalization whenever possible, and weigh risks and benefits of atomizing nebulizing and transtracheal injection techniques.

3. Consider oral intubation as a first-line approach whenever possible.

4. When feasible, performing the ATI through the access ports on a full-facemask device (eg, endoscopic mask) may reduce operator exposure to respiratory secretions.

Anesth Analg. 2021;133(4):876-890. © 2021 International Anesthesia Research Society