is suspected.
In the setting of an anticipated difficult airway, additional tools such as video laryngoscopes, fiberoptic bronchoscopes as well as additional providers with the ability to provide surgical airway access should be immediately available prior to induction.
If intubation and mask ventilation are predicted to be difficult, airway topicalization with local anesthetic and fiberoptic intubation while awake with minimal sedation is the gold standard. This should be performed with an open emergency tracheostomy set nearby as well as a provider capable of performing a surgical airway procedure. One may also attempt an ‘awake look’ by titrating small doses of a non‐apnea‐inducing hypnotic‐like ketamine until a brief exam under video or direct laryngoscopy is tolerated. If this view is acceptable, one can then induce as usual and intubate the patient with the particular device.
In the undesirable scenario where intubation is found to be difficult after induction (unanticipated difficult intubation), an attempt should be made to mask ventilate the patient and assistance should be called. If mask ventilation is easy, one can then attempt another method of intubation while confirming proper positioning and bed height. If mask ventilation is difficult, one should attempt the two‐handed mask ventilation technique or placement of an oral airway. If still difficult, supraglottic airway placement such as an LMA should be considered. If ventilation remains poor, emergency invasive airway placement is likely required.
Cervical spine disease
Cervical spine injury, whether due to trauma, previous cervical fusion resulting in limited mobility, or inflammation from rheumatoid arthritis can present challenges for airway management. The presence of a cervical collar can also make airway management difficult. Evaluation of cervical flexion and extension is prudent, and, in the case of trauma, discussions with spine surgeons regarding cervical spine stability should take place.
In the setting of an unstable cervical spine injury, intubation with a fiberoptic bronchoscope should take place. Alternatively, direct laryngoscopy while an assistant performs inline stabilization (holding the head firmly with both hands so as to not allow unintentional cervical flexion or extension by the laryngoscopist) may be attempted.
Extubation
While the decision to extubate is partly driven by objective data, it also relies upon clinical judgment.
Patients should have stable vital signs, an SpO2 of at least 90% or an FiO2 of 40% or less, PaCO2 <50 mmHg unless there is known chronic CO2 retention, adequate tidal volumes on minimal pressure support, intact airway reflexes, and baseline mental status.
One should also consider the specific situation such as difficulty of intubation, barriers to reintubation (e.g. jaw wired shut after maxillofacial surgery, significant airway edema), fluid balance, and acid–base balance.
If there is any question of airway patency, one may consider performing a leak test (deflating the ETT cuff and listening for air movement around the ETT and observing a decrease in tidal volume) or extubating over an ETT exchanger with a backup ETT available in case reintubation becomes necessary.
Patients with baseline pulmonary dysfunction may benefit from being extubated to BIPAP or HFNC.
Complications of intubation
Airway trauma
Instrumentation of the airway can cause trauma to soft tissues as well as to teeth and lips.
Although less common with modern ETTs, overinflation of cuffs (typically greater than 30 mmHg) can cause tissue ischemia, leading to inflammation and possibly tracheal stenosis as well as vocal cord paralysis from compression of the recurrent laryngeal nerve. Vocal cord paralysis can produce hoarseness and susceptibility to aspiration.
Physiologic effects of airway instrumentation
Hypotension is a common response to induction and should be anticipated, especially in critically ill patients.
Hypertension and tachycardia can be seen if inadequate anesthetic is provided.
Laryngospasm, an involuntary closure of the laryngeal muscles, is a response to airway stimulation in the setting of light anesthesia. Severe hypoxia, from the inability to mask ventilate through the closed larynx, can result. Treatment includes gentle positive pressure with a mask. If this fails, deepening the plain of anesthesia as well as giving succinylcholine will typically relax the musculature.
Aspiration
Critically ill patients often require airway management in the undesirable setting of a full stomach, or mechanical or physiologic motility disorders, making aspiration of gastric contents a feared complication.
If suspected, the patient should be placed in the Trendelenburg position, the pharynx and trachea (if possible) suctioned, and the airway secured with an ETT as soon as possible.
Therapy is typically supportive and antibiotics and bronchoscopic lavage are usually not necessary unless particulate aspiration is suspected or if signs of infection occur.
Reading list
1 Butterworth JF, Mackey DC, Wasnick JD. Morgan and Mikhail’s Clinical Anesthesiology, 5th edition. New York: McGraw‐Hill Education, 2013.
2 Cook TM. A new practical classification of laryngeal view. Anesthesia 2000; 55:274.
3 El‐Orbany M, Woehlick H, Ramez Salem M. Head and neck position for direct laryngoscopy. Anesth Analg 2011; 113:103.
4 Langeron O, et al. Prediction of difficult mask ventilation. Anesthesiology 2000; 92:1217.
5 Miller RD. Miller’s Anesthesia, 7th edition. Philadelphia: Churchill Livingstone/Elsevier, 2009.
6 Robitaille A, Williams SR, Trembaly MH, Guilbert F, Thériault M, Drolet P. Cervical spine motion during tracheal intubation with manual in‐line stabilization direct laryngoscopy: direct laryngoscopy versus GlideScope videolaryngoscopy. Anesth Analg 2008; 106:935–41.
7 Tanoubi I, Drolet P, Donati F. Optimizing preoxygenation in adults. Can J Anesth 2009; 56:449.
8 Watson CB. Prediction of a difficult intubation: methods for successful intubation. Respir Care 1999; 44:777.
Images
Figure 1.1 Mallampati classification.
Additional material for this chapter can be found online at:
