The article describes an anesthetic management strategy for resection of the cervical trachea due to benign stenosis without using an endotracheal tube. The strategy includes: (1) insertion of an airway stent in the stenotic area, (2) insertion of a supraglottic airway device (SGAD), and (3) advancing a jet ventilation catheter through the SGAD. The stent is removed during surgery together with the resected part of the trachea. The technique of nonintubated tracheal resection allows the surgeon to work most comfortably and helps the anesthesiologist properly maintain the patient’s vital functions in the operating room.
The cervical trachea can be resected without endotracheal intubation (nonintubated resection) under jet ventilation performed via a catheter advanced through the supraglottic airway device.
Supraglottic airway device have several advantages compared with endotracheal tubes in the anesthetic management of patients with benign stenosis in the upper part of the trachea.
The use of metal stents for temporary airway recanalization, followed by tracheal resection, is an alternative to traditional methods (eg, bouginage or dilatation), which helps avoid the use of an endotracheal tube.
Preliminary airway stenting and usage of supraglottic airway device makes the formation of tracheal or laryngotracheal anastomosis more convenient compared with traditional endotracheal intubation.
Tracheal resection with direct tracheal or laryngotracheal anastomosis is the best method of radical treatment of benign tracheal stenosis. This approach (especially when stenosis is located in the cervical trachea) is quite simple and, when performed by an experienced surgeon, provides satisfactory immediate and long-term results. Up to 50% of the trachea, whose average total length is 9 to 12 cm, can be safely resected. If a longer part of the trachea needs to be removed, the risk of anastomotic failure and stenosis recurrence increases considerably. That is why numerous surgeons do not consider such resections a feasible option. However, surgery should remain the method of choice for managing the tracheal stenosis that involves less than 50% of the organ length.
Particular attention should be given to lung ventilation during tracheal surgery. Because airway integrity is compromised during surgery, adequate lung ventilation becomes a challenging issue. Intubation, traditionally used during resections, does not seem to be the best option for several reasons.
This article describes an anesthetic management strategy for resection of the cervical trachea due to benign tracheal strictures. The proposed strategy includes the following steps: (1) insertion of an airway stent in the stenotic area, (2) insertion of a supraglottic airway device (SGAD), and (3) advancing a jet ventilation catheter through the SGAD. Owing to the proposed approach, the tracheal patency and ventilation can be maintained during surgery without using an endotracheal tube (ETT).
Conventional methods of anesthetic management in tracheal surgery
Patient preparation for tracheal surgery starts with a thorough consideration of possible outcomes associated with the condition that required prolonged endotracheal intubation or tracheostomy (eg, brain injury, severe myocardial infarction), which led to the tracheal stenosis. Also, limitations arising from concomitant conditions and their management should be taken into account.
Usually, premedication includes mild sedation (anxiolysis) because most patients are very eager to proceed with the surgery and have their airway patency restored as soon as possible. The choice of anesthesia presents hardly any difficulties. Total intravenous anesthesia is commonly used, which uses a combination of agents that helps avoid opioid-induced respiratory depression and agitation. Different general anesthesia techniques may be used at different stages of the surgery; for example, an inhalation anesthetic while the breathing circuit remains airtight and an intravenous anesthetic once the airways have been opened to the outside. Such muscle relaxants should be used during surgery that provide the possibility of safely reversing neuromuscular block when the surgery is finished. Proper ventilation to ensure adequate oxygenation is probably the most challenging issue to address after the tracheal lumen has been opened. Traditionally, this is achieved by the use of intubation anesthesia. An ETT is usually placed in the trachea itself or passed further, to one of the mainstem bronchi. The tube can be introduced in the caudal part of the trachea through the incisional wound (bypass breathing) to maintain convective ventilation, or it can be inserted in the cranial part of the trachea with a thinner tube (catheter) advanced through it to the resection area to perform intermittent jet ventilation once the airways have been opened. Tracheal resection may also be performed under so-called apneic oxygenation. This refers to a technique that, after the airway has been opened, supplies a constant oxygen flow through a thin catheter inserted in the ETT whose distal end is placed right above the resection area. This technique, however, cannot ensure proper elimination of carbon dioxide. Over the last few years, another method of intraoperative oxygenation, extracorporeal membrane oxygenation, has become increasingly scarce in tracheal surgery. Each of the above-mentioned approaches has its benefits and drawbacks.
Benefits and drawbacks of endotracheal intubation
The main advantage of intubation is that it helps successfully control the airway until its integrity has been breached. The end of the ETT is positioned beyond the stenotic area. A flexible endoscope can easily be passed through the tube to the distal part of the trachea to perform airway lavage or correct the position of the tube. After the surgeon has entered the tracheal lumen, a sterile armored ETT is introduced through the incisional wound and passed to the distal part of the trachea; then the tube cuff is inflated and the tube is attached to the ventilator. After that, all manipulations in the surgical area are performed around the tube. Abrupt, rough movements of the surgeon or assistant surgeons may disrupt ventilation airflows. The presence of the ETT at the surgical site makes the work of the surgical team rather inconvenient because it complicates separation of the trachea from the surrounding scar tissue and formation of anastomosis. The tube can be removed from the distal part of the trachea during the most complicated steps of the operation; however, ventilation can be disrupted for 1 or 2 minutes only, and oxygen saturation should be constantly monitored during this period (with the saturation value not dropping below 80%). The use of intubation in tracheal stenosis has still other drawbacks.
When intubation is used during surgery for benign stricture of the cervical trachea, the ETT has to be vigorously pushed through the stenotic area. This is the main drawback of intubation because such pushing inevitably traumatizes the tracheal wall in the area of the future anastomosis. Quite often, intubation requires preliminary dilation of the stenotic area with a rigid bougie; this may result in additional damage to the organ, bleeding, or tear of healthy mucosa. Sometimes, most often in high stenosis, the correct placement of the ETT turns out to be a rather complicated task. Also, the pressure of the inflated cuff may lead to impaired blood flow in the tracheal mucosa, which, in its turn, may affect the anastomosis healing. Although the ETT provides the surgeon with the possibility to easily pass instruments to the distal parts of the trachea and bronchi, the size of these instruments is limited by the internal diameter of the tube, which cannot be very wide because it is used in the stenotic trachea. Also, endoscopic examination of vocal cords cannot be performed while the tube is inside the trachea, even though such examination is sometimes necessary during surgery in the cervical trachea and larynx. Also, the removal of the ETT is not an utterly safe procedure when the anastomosis has already been formed because the anastomotic area may be damaged during extubation. Therefore, it is advisable to prevent the most common drawbacks of intubation so that good immediate and long-term results can be achieved after surgery. Despite the above-mentioned disadvantages of the method, an overwhelming number of surgeons accept the use of intubation during tracheal surgery.
Jet ventilation refers to the delivery of high-pressure ventilation gas into the airway through a thin transtracheal catheter. During jet ventilation, the airway is open to the outside, and the respiratory gas is administered under pressure that is considerably higher than usual. There are several types of jet ventilation; for instance, small tidal volumes may be delivered at high frequencies (high-frequency jet ventilation), or greater volumes may be administered at a substantially lower frequency (normal-frequency jet ventilation). The jet ventilation catheter is usually passed into the trachea through the previously inserted ETT. This anesthetic technique provides adequate ventilation of the lower airways and lungs even when the tracheal lumen is open to the outside. Moreover, the diameter of the jet ventilation catheter does not exceed 3 mm, so its presence in the divided trachea (ie, between the cranial and caudal edges of the diastasis after the stenotic part of the trachea has been resected) causes much less interference with required manipulations and allows the surgeon to bring together the tracheal ends and construct an airtight anastomosis. The jet ventilation catheter can be removed from and reintroduced between the ends of the divided airway without any complications because the tracheal lumen can be quite easily accessed via the ETT.
However, jet ventilation requires intubation of the trachea; therefore, all the drawbacks of intubation previously described are also applicable to jet ventilation.
It should be noted that the use of jet ventilation requires an adequate expiratory pathway; that is, adequate gas evacuation from the distant parts of the trachea and lungs. If the air cannot be properly evacuated, the gas can be trapped in the lungs, which may lead to barotrauma; that is, pulmonary overdistention resulting in a unilateral or bilateral pneumothorax. Also, adequate oxygenation may be hard to achieve in patients with decreased lung compliance. Jet ventilation is often associated with hypercapnia.
The device that uses all the advantages of jet ventilation but lacks the drawbacks associated with intubation is an SGAD.
Supraglottic airway devices
SGADs brands include Laryngeal Mask Airway (LMA) (The Laryngeal Mask Company Ltd., Le Rocher, Victoria Mahe, Republic of Seychelles) and i-gel supraglottic airway (i-gel) (Intersurgical Uab ARNIONI g 60/28-1. LT-16170. PABRADE LITHUANIA), as well as several other devices.
The LMA is a device consisting of an oropharyngeal airway connected to a mask with an inflatable cuff. The air is supplied into the cuff through a nonreturn valve. The LMA is designed in such a way that it forms an airtight seal around the laryngeal inlet, which ensures a secure airway for both spontaneous respiration and mechanical ventilation during general anesthesia.
The LMA was developed by British anesthesiologist Dr A.I. Brain in 1981. The device concept was based on the idea of maximum control with minimum unwanted effects. The i-gel is an analog of a traditional LMA but is equipped with a soft, gel-like, noninflatable cuff that accurately mirrors the perilaryngeal anatomy. The device is inserted into the hypopharynx. A smooth, atraumatic, thin wall cuff forms an airtight seal and reduces the risk of mucosal damage, allowing a safe access to the larynx. The SGAD does not affect vocal cords, which restore their function under spontaneous breathing.
The SGAD is more easily inserted compared with the ETTs because a less reflexogenic area is involved, local anesthesia may not be used, and the patient may be brought back to consciousness sooner. Table 1 compares the use of the ETT and the SGAD in tracheal surgery.
|Proper ventilation||Correct placement is nearly impossible in high stenosis||Achieved regardless of the stenosis location|
|Cough reflex||Elicits||The trachea is not irritated|
|Local effects in pathologic area||ETT cuff affects the blood flow in the tracheal wall||Does not affect the prognosis for anastomosis healing|
|Appropriate endoscopic control of vocal cords and tracheobronchial tree||Limits||Allows|
|Endoluminal passage and control of equipment||Limited by the ETT diameter||Allows|
|Removal after surgery||Requires thorough control||Safer |
Reduces the risk of prolonged mechanical ventilation