Stents

If primary removal or correction of airway lesions is not possible, other means of assuring an airway must be found. These include tracheostomy tubes, T tubes, and stents.34,35

Tracheostomy. The standard tracheostomy should be familiar to all practitioners. It can be performed under topical anesthesia in impending airway obstruction, or on a patient with an endotracheal tube in place. The management is similar to reconstructive surgery, except that extubation, neck flexion, and concerns about upper airway obstruction are not present.

The indications for tracheostomy include facilitating controlled ventilation, protection of the airway against aspiration and bleeding, and allowing airway access distal to an obstructed or damaged portion. Tracheostomy is also commonly performed in patients requiring prolonged intubation since it is more comfortable and less injurious to vocal cords than orotracheal or nasotracheal intubation. There has to be special consideration of gas humidification since the function of the nasopharynx is bypassed. If no humidification and cleaning is done, then the tube will eventually become obstructed with secretions. Voice can be preserved via a number of tube modifications, including choosing not to use a cuff or choosing a tube with a special fenestration.

figure 18-4 Endobronchial tube made from a modified endotracheal tube. The tracheal lumen is removed from the distal portion of the tube. The endobronchial design is excellent, but different for right and left bronchi.

When presenting for another procedure, a patient with a tracheostomy tube can either be ventilated through the existing tube, or the tracheostomy tube can be exchanged for a cuffed endotracheal tube passed through the tracheostomy stoma. It is unwise to remove a fresh tracheostomy tube since the stoma has not yet healed and the replacement tube can easily enter another tissue plane. If a tube is placed, attention must be paid to the depth of insertion, since the length to the carinal bifurcation can be deceptively short. The effectiveness of ventilation will also depend on whether there is a cuff in place, or whether the inner can-nula that covers the fenestration of a fenestrated tube is in place.

T Tube. The T tube is an uncuffed tube that sits in the trachea, and is held in place by the sidearm through a tracheostomy stoma. It is designed to bridge any diseased portion of the trachea, allowing full voice and mouth breathing. The tracheostomy segment is typically capped, but can be opened if there is a proximal obstruction, and for suctioning (see Chapter 39, "Tracheal T Tubes").

Placement is done in an anesthetized patient, with the folded tube placed through the stoma and springing into proper position. Evaluation via flexible bronchoscopy through the sidearm, and rigid bronchoscopy from above, will also show adjustments that need to be made. The procedure can take many iterations to find the optimal size and length for each segment. At times, the tube may lie in a folded state in the distal trachea, completely obstructing the airway. The anesthesiologist needs to recognize this promptly and provoke correction or removal. There will be extensive apneic periods during placement and manipulation, requiring coordination between the anesthesiologist and the surgeon. In the interlude, a small endotracheal tube can be placed in the stoma, or the stoma can be covered and ventilation accomplished through the rigid bronchoscope.

At the end of the procedure, the patient should be ready to resume spontaneous ventilation. Blood and secretions can precipitate an acute obstruction, so close observation, suctioning, and even removal of the tube may be needed. Although the goal is to cap the sidearm, there may be enough swelling of the larynx after all this manipulation to delay capping for a few hours. Humidified oxygen applied to the stoma will be needed.

If a patient with a T tube in place comes for unrelated surgery, there are several options. Regional techniques, where appropriate, will avoid airway manipulation. An LMA can be placed, and the sidearm left capped. The tube will then perform its function as a tracheal stent. The sidearm can be accessed by removing its cap and placing the adapter to an appropriately sized endotracheal tube. In this case, the trachea is open above, and ventilation will depend on the relative resistance of the two arms. The upper arm can be obstructed by a blocker, placed via laryngoscopy or placed via the sidearm, and cajoled into sitting in the proximal lumen. Finally, the T tube can be entirely removed and replaced with a tube through the tracheostomy. The choice of method should depend on the nature of the procedure and the predicted postoperative course.

Endoluminal Stents. Endoscopically placed stents can be silicone tubes or expanding wire devices (see Chapter 40, "Tracheal and Bronchial Stenting"). The stents are placed directly via a rigid bronchoscope, or using a flexible guidewire placed with a flexible bronchoscope. Rigid bronchoscopy allows ventilation through the bronchoscope, whereas flexible bronchoscopic techniques require intermittent ventilation with a mask, tube, or jet catheter.36 The major anesthetic considerations, besides the underlying tracheal pathology, is the chance that a poorly positioned stent will completely obstruct the airway. As with T tubes, the stent, once deployed, may need minor corrections to improve its function, so an anesthetic of unpredictable duration ensues. On emergence, patients tend to find the stent irritating, and can cough it out of position. The patient will need to be reinduced and the process restarted. Assessment of the adequacy of air movement, and maneuvers to improve the airway, such as nebulized epinephrine and a short course of steroids, may be needed.

When a patient with a stent presents for unrelated surgery, many of the considerations for patients with T tubes pertain. Regional techniques and the LMA will avoid tracheal manipulation. If it is necessary to secure the airway, all the information available on the stent and the underlying tracheal lesion should be collected (probably a wise precaution even if intubation is not planned). The location of wire stents can be seen on an x-ray. If the stent is relatively distal, then a tube placed in the proximal trachea may not impinge. The tube should be placed under fiber-optic guidance, and care must be taken not to allow it to move during patient positioning. Although it is possible to intubate into or beyond the stent, there is the real risk of dislodging the stent, either by pushing it distally and causing obstruction, or by inadvertently removing it on extubation and leaving a vulnerable trachea. With time, wire stents become embedded into the tracheal wall, and potentially become more secure, but the extent and safety of this is not yet known.

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