Lung Isolation in Patients With a Difficult Airway in Thoracic Anesthesia




Lung Isolation in Patients With a Difficult Airway in Thoracic Anesthesia



Javier H. Campos



Abstract


Patients who present with a difficult airway and require one-lung ventilation represent a challenge for the anesthesiologist. During the preoperative period, review of the posterior-anterior chest radiograph is necessary to measure the tracheal width and appreciate the pattern of the tracheobronchial anatomy to determine what device and size to use. Also a multidetector computed tomography scan of the thorax, with particular interest in tracheobronchial anatomy, must be reviewed as part of the preoperative assessment. The left-sided double-lumen tube is the most common device used for lung isolation because of its greater margin of safety. The use of bronchial blockers is indicated in patients who present with difficult airways and require lung isolation. Patients with a tracheostomy in place requiring lung isolation are best managed with the use of an independent bronchial blocker and flexible fiberoptic bronchoscopy. Flexible fiberoptic bronchoscopy is the recommended method to achieve optimal position of lung isolation devices, first in supine position, later in lateral decubitus, or whenever a malposition occurs.


Keywords


preoperative assessment; upper and lower airway abnormalities; lung separation; double-lumen endotracheal tubes; bronchial blockers; flexible fiberoptic bronchoscopy; multidetector computer tomography scan of chest



Introduction


One-lung ventilation (OLV) in the thoracic surgical patient who presents with a difficult airway can be achieved with the use of a single-lumen endotracheal tube with a bronchial blocker or with the use of a double-lumen endotracheal tube (DLT).1–4 It is estimated that between 5% and 8% of the patients who presented for thoracic surgery for primary lung carcinoma also have carcinoma of the pharynx, usually in the epiglottic area. Many of these patients have undergone extensive surgery of the airway or neck.3 In addition, some of these patients had previous radiation to the neck or previous airway surgery, such as hemi-mandibulectomy or hemi-glossectomy, making intubation difficult in general, and particularly for achievement of OLV because of distorted upper airway anatomy. The distorted anatomy can be located at or beyond the tracheal carina, such as descending thoracic aortic aneurysm compressing the left mainstem bronchus or an intrabronchial or extrabronchial tumor near the tracheobronchial bifurcation that make the insertion of a left-sided DLT difficult or impossible.5



Preoperative Assessment of the Difficult Airway


An airway is termed difficult when conventional laryngoscopy reveals a class III view (just the epiglottis is seen) or class IV view (just part of the soft palate is seen). Fig. 17.1 displays the airway anatomy and class III and IV according to the modified Mallampati classification. Once the airway is recognized as being potentially difficult, a careful examination of the patient should follow. Previous anesthesia records, if available, should be examined for a history of airway management of the patient. Patients should be asked to open their mouths as wide as possible and extend their tongues. The length of the submental space should also be noted. Patients should be evaluated from side to side to assess any degree of maxillary overbite and their ability to assume the sniffing position. Also the patency of the nostrils must be assessed in patients who cannot open their mouths because a nasotracheal approach might be considered.6 For patients who have a tracheostomy in place, the inlet of the stoma and the circumferential diameter must be assessed when considering replacing the tracheostomy cannula with the device selected to achieve OLV.7 Furthermore, depending on the type and the length of surgery, the degree of fluid shift during surgery, an airway that initially was not classified as difficult may become difficult secondary to airway edema, the presence of secretion, and laryngeal trauma from the initial intubation. In addition, 10% of the patients who can be intubated with a single lumen tube can be difficult to insert a DLT into depending on the degree of the mouth opening, the size of the tongue and the composition of the teeth.


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• Fig. 17.1 Modified Mallampati classification for difficult laryngoscopy and intubation. (A) Normal airway anatomy, (B) class III, just the epiglottis is seen, and (C) class IV, where just part of the soft palate is seen.

Another group of patients considered to have a difficult airway during OLV are those who have distorted anatomy from compression or intraluminal tumor at the orifice of the mainstem bronchus.5 Such anomalies can be recognized by reviewing chest radiographs and multidetector computed tomography scans to determine the main stem bronchus diameter and anatomy to exclude the presence of distortion or compression.8 In some cases, the use of flexible fiberoptic bronchoscopy will be necessary to evaluate the degree of distorted anatomy of the airway before the selection of a specific device to achieve OLV. Box 17.1 displays the patients at risk of potentially having difficult intubation during OLV.3



• Box 17.1


Patients With Potential Risk of Having a Difficult Airway During One-Lung Ventilation


Upper Airway


Short neck and increased neck circumference >42 cm


Prominent upper incisors with a receding mandible


Limited cervical mobility and compression of spinal cord


Limited jaw opening, that is, chronic trismus


Radiation therapy to the neck region


Hemi-glossectomy/hemi-mandibulectomy


Large tumor of the tongue, mouth, and epiglottis


Lower Airway


Existing tracheostomy in place


Distorted anatomy within trachea or bronchus


Compression at the entrance of right or left mainstem bronchus



Difficult Airways and Lung Isolation: Primary Objective to Secure the Airway


In patients who require OLV and present with a difficult airway, the primary initial goal is to establish an airway with a single-lumen endotracheal tube. Any concern regarding the possibility of losing control of the patient’s airway during the induction of anesthesia mandates an awake fiberoptic intubation, following an adequate topicalization of the airway. In selected patients who seem easy to ventilate, this may be performed after induction of anesthesia with the use of a bronchoscope or with one of several clinically available video laryngoscopes such as the C-MAC blade, GlideScope, King Video laryngoscope, or the Airtraq. All these devices have been shown to facilitate the view of epiglottis and vocal cords.9–11



Upper Airway Abnormalities and Lung Isolation


Patients requiring OLV can be identified during the preoperative evaluation to have a potentially difficult airway from distorted airway anatomy caused by previous surgery, radiation therapy with stiff tissues or both. Various methods are available to provide OLV under these circumstances. As mentioned previously, the first step is to establish an airway with a single-lumen endotracheal tube placed orally when the patient is awake, using a flexible fiberoptic bronchoscopy.


During the preparation for an awake fiberoptic intubation, the patients should receive oxygen via a nasal cannula and be fully monitored with electrocardiogram, blood pressure, and pulse oximetry. All local anesthetics used via spray or aerosolizer should be quantified to avoid complications from overdose of local anesthetic, such as seizures. Also, these patients should receive an antisialagogue medication, such as glycopyrrolate.


A simple approach to anesthetize the posterior part of the tongue is to apply lidocaine 5% ointment to a tongue blade depressor, and let the patient hold this in the mouth for 5 minutes. After the tongue blade depressor is removed, a mucosal atomization device to spray a local anesthetic with lidocaine 4% directly to pharynx, larynx, and vocal cords should be used. When the patient experiences a cough reflex, it is very likely that the anesthetic has entered the vocal cords.


The next step is to suction all residual secretions that were accumulated in the airway. To test that the gagging reflex is abolished, a Berman intubating pharyngeal airway impregnated with lidocaine 5% ointment at the posterior tip end of the cannula is advanced in the middle of the tongue until it is completely inserted in the oral cavity. The advantage of using the Berman cannula is that it facilitates a view of the epiglottis and allows the direct passage of the fiberscope followed by a single-lumen endotracheal tube. Also, the rigid cannula protects the fiberscope against potential damage from the patient’s teeth. The fiberscope must be positioned in the midline such that the single-lumen endotracheal tube faces posteriorly during the attempt for intubation. In some cases, retracting the single-lumen endotracheal tube in a 90-degree counterclockwise rotation will disengage the tip of the tube from the vocal cord and facilitate passage of the tube into the trachea.


Following placement of the fiberoptic bronchoscope and the single-lumen endotracheal tube within the patient’s trachea is the direct visualization of the tracheal rings and the tracheal carina with the fiberscope, along with the view of the tip of the single-lumen endotracheal tube inside the trachea.12 After the patient is intubated with a single-lumen endotracheal tube, then an independent bronchial blocker should be used to achieve OLV.


Common independent bronchial blockers used through, or extraluminal to, the single-lumen endotracheal tube include: a wire-guided endobronchial Arndt blocker sizes 5.0, 7.0, and 9.0 Fr, the Cohen Flexitip blocker size 9.0 Fr, the Fuji Uniblocker sizes 4.5 and 9.0 Fr, or the EZ-Blocker size 7.0 Fr.13 An alternative for securing the airway if a patient cannot open the mouth because of previous surgery and cannot be intubated orally, is an awake nasotracheal intubation, which can be performed taking all precautions of a nasal intubation, including the application of a vasoconstrictor, followed by a local anesthetic, and the passage of a single-lumen endotracheal tube. Once the airway is established, then an independent bronchial blocker can be advanced under direct fiberoptic view to the selected main bronchus.14


When an independent bronchial blocker is used, specifically, size 9.0 Fr, (the smallest acceptable single-lumen endotracheal tube size recommended is 8.0 internal diameter (ID) mm), it is important to have enough space between the bronchial blocker and the flexible fiberoptic bronchoscope so that navigation can be achieved with the single-lumen endotracheal tube. If only a 7.0- or a 7.5-mm single lumen tube was able to be placed, the 9.0 Fr blockers can still be positioned. Following an extensive lubrification of the blocker, it should be passed first blindly to have the blocker cuff beyond the tip of the single lumen tube. Then, the insertion of the fiberoptic bronchoscope will follow for proper positioning. That will avoid having the blocker cuff, which is the limiting factor, and the bronchoscope together in the narrow single lumen tube. An advantage of the Cohen Flexitip, Fuji Uniblocker, or the EZ-Blocker over the Arndt wire-guided endobronchial blocker is that while advancing it to a desired bronchus, the distal tip of the blocker can be seen by the bronchoscope while being directed to the selected bronchus. With the Arndt blocker, the distal tip is looped into the fiberscope and cannot be visualized until disengagement occurs. Because this blocker is advanced blindly, it can be caught in the Murphy eye of the endotracheal tube or at the carina. One of the advantages of the use of a blocker in a patient with a difficult airway, in addition to providing OLV with insertion of a single-lumen endotracheal tube, is that the independent bronchial blocker is simply removed at the end of the procedure if postoperative ventilatory support is needed.15 The blocker balloon should be inflated only once the patient is turned to the lateral decubitus position. The amount of air needed to achieve a complete seal within the bronchus in an adult varies between 5 and 8 mL. The EZ-Blocker requires higher amounts of air to achieve a seal.16 It is best to inflate the blocker cuff under direct vision with the bronchoscope.


The optimal position of a bronchial blocker in the left or right bronchus is when the blocker balloon’s outer surface is seen at least 10 mm below the tracheal carina inside the blocked bronchus and a proper seal is achieved. Fig. 17.2 shows the optimal position of the Fuji Uniblocker through a single-lumen endotracheal tube. Fig. 23 in Chapter 16 shows the optimal position of an EZ-blocker. Following the inflation of the blocker cuff, the blocker lumen can be attached to a suction while observing the ventilator bellows. If the bellows fail to fill up, it is an indication that the inflated bronchial cuff is not adequately sealing the main bronchus lumen and the tidal volume is being lost.


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• Fig. 17.2 The optimal position of the Fuji Uniblocker through a single-lumen endotracheal tube. (A) Fully inflated balloon of the Fuji Uniblocker in the right mainstem bronchus. (B) Fully inflated balloon of the Fuji Uniblocker in the left mainstem bronchus.


Use of Laryngeal Mask Airway and a Bronchial Blocker During Difficult Airways


An alternative to achieve OLV in a patient with a difficult airway is with the use of a laryngeal mask airway in conjunction with the use of an independent bronchial blocker. The ProSeal laryngeal mask airway has been used with a bronchial blocker in patients in whom the airway was deemed difficult and who required OLV during thoracoscopic surgery.17,18

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Oct 6, 2021 | Posted by in ANESTHESIA | Comments Off on Lung Isolation in Patients With a Difficult Airway in Thoracic Anesthesia
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