Anesthesia for Tracheobronchial Surgery

Abstract

The airway is a crucial dynamic structure that spans different anatomical zones, including the intrathoracic, extrathoracic, tracheal, bronchial, and alveolar zones. Because of its vital role as the sole oxygen-conducting pathway to the alveoli, and hence to the human body, surgery involving any portion requires careful and specific planning by both the surgeon and the anesthesiologist. The review covers essential management points for proximal and distal tracheal procedures, including a discussion of tracheal stenting and tracheoplasty.

Keywords

thoracic surgery analgesia noncardiac surgery oxygen delivery intraoperative assessment

Introduction

Airway surgery represents a challenge to the surgeon, the anesthesiologist, and the intensivist. There are few other surgical areas that require such close planning and communication between these 3 teams because any miscalculation requires immediate resolution to avoid catastrophic consequences for the patient. For example, surgeons are often present at induction in case an emergent surgical airway is needed. Additionally, multiple airway control techniques may be needed in a single case, such as when a flexible fiber-optic exam is performed through an LMA (laryngeal mask airway) prior to the definitive surgical repair. Postoperatively, the intensivist should have a detailed understanding of the new airway anatomy and options for reestablishing an airway in the event of airway compromise. In this review, we will outline several airway management techniques often used in thoracic anesthesia as well as the anesthetic considerations for some less-common airway surgeries. The techniques will be divided into considerations based on the location of the pathology from proximal to distal. The goal is to outline a practical approach to these complex operations and provide an overview of the most commonly used techniques. Following the main discussion, Appendices A to D provide detailed information on management techniques suggested in the text, including single-lung ventilation, cross-field ventilation, jet ventilation, and intermittent apnea.

Proximal Tracheal Surgery

Tracheal resection is most often performed for postintubation stenosis or tumor resection. Risk factors for postintubation stenosis include duration of intubation, endotracheal tube cuff overinflation, repetitive movement of the endotracheal tube, low perfusion states, infection, and comorbid conditions such as diabetes.^1,2 Other etiologies for stenosis include congenital lesions, tracheoesophageal fistula, and infectious/inflammatory pathology. Tracheal stenosis generally becomes symptomatic at a tracheal diameter of 5 to 6 mm.² Patients are often initially misdiagnosed as having adult onset asthma. One should have clinical suspicion when a patient with previous instrumentation of the trachea develops exertional dyspnea without parenchymal pathology, stridor, or wheezing.^1,2

Classically, tracheal resections involve the extrathoracic trachea. The surgical approach is through a midline neck incision, with the 2 edges approximated. This essentially results in part of the intrathoracic trachea becoming extrathoracic. Keeping tension off of the new suture line is an essential part of the healing process and, therefore, of operative success. Less commonly, if the resected section is the intrathoracic trachea, the approach may be through thoracotomy.

Preoperative evaluation should include a detailed conversation about symptoms related to the stenosis, airway exam, and radiographic findings. An important part of the preoperative assessment that can significantly affect anesthetic planning is to seek answers to the following questions:

Can the patient clear secretions? If not, this could suggest weakness of respiratory muscles or increased risk of airway plugging from potentially viscous secretions.

Is the patient stridulous just with activity or also at rest? If the patient is stridulous at rest, this suggests a more clinically relevant degree of obstruction.

Are there any symptoms when supine? Symptoms when supine suggest a greater risk of complete airway obstruction when supine with induction. If there is concurrent concerning radiographic data, this may point toward an awake fiber-optic intubation. Make an airway plan with the surgeon.

How is the neck mobility? Patients must remain with the neck flexed postoperatively. This could be problematic if they are limited preoperatively.

What did the 3D tracheal reconstruction and bronchoscopy show? This can be helpful for understanding the severity of obstruction in patients who are poor historians or physically inactive.

Are there any additional data from pulmonary function tests (PFTs), spirometry, or chest X ray? Are all their symptoms a result of their tracheal obstruction, or do they have coexistent parenchymal disease as well? If there is coexistent obstructive or reactive lung disease, is the patient well controlled? Is there suggestion of need for postoperative mechanical ventilation, and would this cancel surgery?

PFTs may be used early to differentiate airway pathology from primary lung pathology; however, direct examination by flexible bronchoscopy and possible rigid bronchoscopy provides the definitive surgical information. A complete review on PFT utilization in lung resection surgery was recently presented in this journal by Bernstein and Deshpande³ and serves as a complete review for both airway lesions and thoracic lung masses requiring resection. Additionally, the review by Blasberg and Wright that accompanies this article provides the surgical approach and discussion of airway lesions, including methods in preoperative planning for tracheal resection.⁴

Patient education is critical. The patient must understand why they must keep their neck flexed, that they will awake with a chin stitch, and that they will most likely feel some difficulty breathing regardless of how well they are oxygenating. Care should be taken in giving preoperative anxiolysis because of the risk of respiratory depression, and this is best held until the patient is actually in the operating room. Preoperative discussion with the surgeon regarding the degree of obstruction and airway management plans is essential.² If the surgical approach is through a thoracotomy, a thoracic epidural catheter for postoperative pain control should be discussed.

The anesthetic setup should include multiple, sterile endotracheal tubes, cuffed and uncuffed, regular length and long, and regular and flexible armored, from size 4 to 8 mm. A sterile anesthesia circuit with a sterile carbon dioxide monitoring line is prepared for cross-field ventilation (Figure 1.). Arterial monitoring is placed for arterial blood gas analysis both intraoperatively and postoperatively. As both arms are tucked for this procedure, a second intravenous line should be considered.

Induction medications should be chosen based on the patient’s comorbidities, and despite the stenosis, awake fiber-optic intubation is usually not necessary. A “difficult airway” can make visualization via emergent rigid bronchoscopy difficult. If there is concern for or knowledge of a difficult airway, then an awake flexible bronchoscopy can be performed for sizing of the airway. If this approach is taken, the airway should be well topicalized and the patient not induced until the appropriate sized endotracheal tube has been passed through the obstructed area. Maintenance of anesthesia should be through a total intravenous approach in either case.

After induction, if the above awake procedure is not performed, an LMA is often placed, through which the surgeon will perform a flexible bronchoscopic exam. The purpose of the bronchoscopy is to size the airway. After the tracheal size has been ascertained, the trachea is intubated with a cuffed, standard-length, appropriately sized endotracheal tube. Intraoperative management involves a true “sharing of the airway” and thus requires meticulous communication between the surgeon and the anesthesiologist. After the trachea is opened, the distal trachea is intubated on the surgical field by the surgeon with a flexible armored endotracheal tube (Figure 2.) A sterile anesthesia circuit with a sterile CO₂ line is passed through the drapes for cross-field ventilation (Figure 3). Close communication between the anesthesiologist and the surgeon is critical at this phase. The oral endotracheal tube is pulled back from the operative area but left below the vocal cords. The oral endotracheal tube will be used for airway management later. Additionally, if a different-sized endotracheal tube is needed at the end of the case, it can function as a conduit for exchange. Often a suture or a rubber string is attached through the eye to avoid accidental extubation.

During the tracheal anastomosis period, intermittent apnea is generally the preferred method of ventilation. Jet ventilation is an option at this phase but because of the potential for airway barotraumas, it is usually avoided. During intermittent apnea, clear communication with the surgeons is essential. After completion of the anastomosis, the oral endotracheal tube is advanced and passed through the anastomosis site with the discontinuation of cross-field ventilation. Please see appendices A, B, and D for further discussion of cross-field ventilation, intermittent apnea, and jet ventilation, respectively.

Positive-pressure ventilation can cause significant tissue trauma by putting tension on the suture line; thus, extubation at the end of the case is critical. Controlled emergence is necessary, which can be achieved either with an opioid wake up or with a dexmedetomidine infusion. Gagging, coughing, and neck extension during emergence needs to be minimized. Intravenous lidocaine prior to emergence may mitigate coughing. Pillows and the chin stitch help minimize neck extension. The patient should be completely awake and following commands prior to extubation. After extubation, vocal cord function can be assessed by asking the patient to phonate.⁵

In the immediate postoperative period, a calm, normally breathing patient is desirable. Anxiety if present needs to be monitored and carefully controlled. If respiratory distress develops postoperatively, the surgical team should be notified immediately. In terms of the etiology of respiratory distress, the diagnosis is most commonly differentiated between anxiety, vocal cord dysfunction, and/or obstruction from airway edema. An arterial blood gas can help differentiate anxiety from a true problem with oxygenation and/or carbon dioxide retention. In the event of respiratory compromise following extubation, reintubation should be the last resort because of concerns of trauma to the anastomosis site. Bronchospasm should be treated with a bronchodilator. Airway edema can be treated with a racemic epinephrine nebulizer. Distress from persistent coughing or airway irritation may be mitigated with a 4% lidocaine nebulizer. If efforts to avoid intubation fail, then fiber-optic bronchoscopy is preferred for reintubation. An uncuffed endotracheal tube is the first choice because it minimizes contact with the anastomosis. When a cuffed endotracheal tube must be used, it should be positioned with the cuff distal to the anastomosis. During reintubation, the vocal cords and anastomosis site should be visually examined. Postrecovery room disposition should always be the intensive care unit.

Surgery Involving Long Tracheal Segments: Tracheal/Endobronchial Stenting and Posterior Splinting Tracheoplasty

The most common indication for tracheal surgery involving long segments is acquired or idiopathic tracheomalacia or tracheobronchomalacia. Acquired tracheomalacia/tracheobronchomalacia can be focal or diffuse. Loss of integrity in the anterior cartilaginous rings or the posterior wall leads to dynamic obstruction.⁶ Focal lesions tend to be secondary to mechanical insults such as goiter, vascular abnormalities, tracheostomy, endotracheal intubation, chest trauma, postsurgical state (eg, pulmonary resection), and malignancy. Diffuse tracheal lesions or tracheobronchomalacia can be caused by chronic irritation and inflammation.⁷ There is also an association with tracheomalacia/tracheobronchomalacia and chronic obstructive pulmonary disease.^6,8 Tracheomalacia/tracheobronchomalacia can also occur without identifiable etiology.

MRI, CT, and PFTs have all been used to attempt diagnosis of tracheomalacia/tracheobronchomalacia. Despite attempts with these modalities, bronchoscopy with spontaneous respiration remains the gold standard. Dynamic MRI or CT may show expiratory collapse of the airway and rule out other causes. PFTs may show abnormal flow volume loops.⁹ With bronchoscopy, severe, moderate, and mild tracheomalacia/tracheobronchomalacia are defined as a meeting of the anterior and posterior walls, loss of 75% of the original lumen size, and loss of 50% of the original lumen size, respectively. Airway narrowing usually occurs with expiration.^6,8

Tracheomalacia and tracheobronchomalacia can be palliated or surgically corrected. Posterior splinting tracheoplasty is an operative technique used to increase the airway diameter. Tracheal stenting can be palliative or part of the presurgical evaluation of tracheomalacia/tracheobronchomalacia. After diagnosis of tracheomalacia/tracheobronchomalacia and prior to tracheoplasty, a silicone stent is placed with a rigid bronchoscope under general anesthesia. If the patient has symptomatic improvement with stenting, this suggests that they will benefit from tracheoplasty. The stent is removed prior to tracheoplasty, and the patient is allowed recovery time prior to surgical intervention.

When performing preoperative evaluation of patients with tracheomalacia/tracheobronchomalacia, ask the patient what factors exacerbate their airway collapse. Unless there are contraindications, a thoracic epidural should be placed pre-operatively for post-operative pain control if posterior splinting tracheoplasty is planned. Posterior splinting tracheoplasty also warrants 2 large-bore intravenous lines, an arterial line, and type and screen (see below for further description of posterior splinting management).

Premedication should be used judiciously as avoidance of respiratory distress prior to airway control is essential. There is nothing unique regarding the method of induction because both positive-pressure mask ventilation and endotracheal intubation with positive pressure ventilation minimize the collapse of the affected segments. However, prior to induction, the need for bronchoscopy and spontaneous ventilation should be discussed with the surgeon. Though the patient most likely will have undergone bronchoscopy prior to coming to the operating room, the surgery team may want to repeat it in the operating room prior to surgical correction. If flexible bronchoscopy is performed, it is generally through an LMA. The surgical team may actually need the patient to cough in order to see the full degree of airway obstruction.

Tracheal and Endobronchial Stents

Endobronchial stents have been used in both surgical evaluation for and treatment of tracheomalacia/tracheobronchomalacia. Though endobronchial stents are not generally considered definitive therapy for tracheomalacia/tracheobronchomalacia, the use of expandable metal stents has been described in patients not physically fit for operative repair. These can be placed with a flexible bronchoscope under conscious sedation.¹⁰ Complications of airway stents include infection, granulation tissue formation, mucociliary transport arrest, and migration. Metallic stents can fracture, and if this occurs, they must be removed. There is less migration with metallic stents than with silicone stents.⁹ The dynamic nature of tracheomalacia/tracheobronchomalacia makes stent migration a larger issue than when stents are used in static lesions.

Endobronchial stents may be placed with a flexible or rigid bronchoscope depending on the type of stent being placed. If a rigid bronchoscope is to be used, then a general anesthetic with intravenous maintenance is necessary. One can manage the airway through the rigid bronchoscope with intermittent ventilation and apneic oxygenation. If a flexible bronchoscope is used, then the procedure can be performed under conscious sedation, and no further airway management may be required. If general anesthesia is used, maintenance should be through a continuous intravenous approach.

External tracheal stenting uses synthetic materials to act as surrogate anterior tracheal rings in malacic segments, ideally to expand the trachea without opening it.¹¹ External tracheal stenting has been described with multiple materials, including silastic rings, ceramic rings, and titanium plates. This replacement of the anterior rings appears most amenable to the extrathoracic trachea. Complications include damage to the recurrent laryngeal nerve and erosion into abutting blood vessels.¹¹ If titanium plates are used, emergent tracheostomy may be difficult because the rings are not easy to remove. The ceramic rings can be broken and removed without significant problems.¹¹ External tracheal stenting is extrathoracic and extratracheal, and as such, management with a standard single-lumen endotracheal tube and anesthetic is appropriate. Bronchoscopy may be performed prior to operative repair. Neuromonitoring may be used secondary to proximity of the recurrent laryngeal nerves and operative field.¹¹

Posterior Splinting Tracheoplasty

Posterior splinting tracheoplasty is a method of surgical correction for tracheomalacia or tracheobronchomalacia. It involves sewing the redundant posterior wall tissue to a splinting material. The splinted areas usually include the intrathoracic trachea, both mainstem bronchi, and the bronchus intermedius. Repair is carried out with 3 pieces of material—first placed at the thoracic inlet to the carina, then the left mainstem to the carina, and followed by the bronchus intermedius to the carina. At this point, the ends of the grafts meeting at the carina are sewn together. The surgical approach is via a right posterolateral thoracotomy and involves ligation of the azygous vein and division of the right vagus nerve and its branches. Endobronchial stenting is performed prior to surgical correction to determine if the patient will benefit from tracheoplasty.¹² A complete discussion on the surgical approach for tracheomalacias is presented in the accompanying article by Damle and Mitchell.¹³

Posterior splinting tracheoplasty can be a challenging case of airway management and lung isolation. One-lung ventilation (left) facilitates surgical exposure because the surgical approach entails sewing into the posterior wall of the trachea and bronchus. A standard double-lumen endotracheal tube is too large, resulting in significant anatomical distortion, making surgical repair difficult. Bronchial blockers can be used to deflate the right lung during exposure; however, this approach also creates distortion in the right bronchus, complicating the procedure. An extralong, small-diameter, single-lumen endotracheal tube is ideal because it allows suturing the mesh to the membranous posterior wall while allowing lung isolation by inserting the tube into the left main bronchus. Long, very flexible tubes of small diameter but sufficient length (>31 cm) to reach the bronchus are newly available and marketed by Fuji systems, and are available with internal diameters of 5.5, 6.5, and 7.5 mm (Table 1). Note that the tip design in endobronchial tubes is important. The Fuji tube has a very small cuff designed for endobronchial applications (Figure 4). This endobronchial tube is positioned under fiber-optic guidance. The long, flexible design of these tubes as well as the extensive surgical manipulation of the region causes frequent tube malposition. Fortunately, because the surgical field is at this site, the surgeon can manually direct the tube into position should this occur during the procedure. A fiber-optic scope should be constantly at hand because the anesthesiologist will be required to make frequent corrections throughout the operation. Please see Appendix C for further discussion of single-lung ventilation.

Table 1.

LMA Product, Fuji Systems, Japan^a

ID (mm)	Product Number
5.5	1200824
6.5	1200828
7.5	1200831

Abbreviations: LMA, laryngeal mask airway; ID, internal diameter.

From LMA North America, http://www.lmana.com/files/product_catalog_july_2011.pdf (page 2).

Jet ventilation is an alternative; however, there are significant disadvantages to this technique. High-frequency jet ventilation can cause barotrauma. Low-frequency jet ventilation can result in significant desiccation of the tracheal mucosa. Intermittent apnea may be used for posterior splinting tracheoplasty. With this technique, the patient’s airway is secured with a single-lumen tube in the trachea. When the surgeon is ready to commence sewing on the airway, the single-lumen tube is retracted to the thoracic inlet, and intermittent apnea ensues. This is somewhat cumbersome for the surgeon because during times of ventilation, the lung needs to be held out of the way, but it does allow for optimal sewing conditions on the airway. Please see Appendices D and B for further discussion of intermittent apnea and jet ventilation, respectively.

Maintenance of anesthesia should be with total intravenous anesthesia. Oxygenation and ventilation should be monitored via arterial blood gas sampling. Thoracic epidural is an excellent and preferred choice for pain control, and if present, it should be dosed prior to emergence (Please see section on postthoracotomy pain below).Unless individual patient factors preclude it, extubation should be done in the operating room. Note that tracheomalacia may extend past the region surgically corrected, so be prepared for airway obstruction to be present to some degree postoperatively. The patient should be watched in the intensive care unit postoperatively.

Distal Tracheal Surgery: Carinal Resection and Reconstruction

Lesions near the carina add some new challenges to the process of tracheal resection and reconstruction discussed above.^14,15 Carinal lesions are generally secondary to trauma, lung cancer, or intrinsic tracheal tumors. Diagnostic and preoperative considerations are similar to those for patients undergoing tracheal resection, although the importance of imaging and coordination is increased for planning the surgical approach and airway management. Because these lesions may involve lung resection and need for 1-lung ventilation, PFT testing serves as a useful predictive tool and has been described in detail previously.³ The procedure is intrathoracic, usually approached from a thoracotomy or median sternotomy, and the lungs cannot be treated as a single entity. As in all thoracotomies, arterial monitoring is prudent, and methods of postoperative analgesia, such as thoracic epidural catheters, are indicated (Please see section on postthoracotomy pain below). Otherwise, the room setup is similar to tracheal resection. Cross-field ventilation is standard, and it may be necessary to ventilate each lung independently.

The considerations for induction of anesthesia are similar to surgery for higher lesions, although it is even more clear that surgical access to the airway in the case of complete obstruction (ie, rescue tracheostomy) is not an option. Some authors suggest venovenous bypass as a fallback technique.¹⁶ Once the bronchoscopic examination is completed, it is time to intubate the trachea. There are several options. If the degree of airway compromise is minimal, the tube can be placed above the lesion. The trachea will often be approached via thoracotomy and the airway entered. Exposure cannot be assisted by collapse of the lung unless a blocker is passed into the surgical side. If the bronchus is already damaged, a blocker would be unwise, so small tidal volumes and lung compression in the field are required. Once the trachea is entered, a tube is passed on the field into the opposite mainstem bronchus, and single-lung ventilation is used.

Some lesions are better addressed by distal intubation from the start. Because the lesion is at or beyond the carina, the only option is endobronchial intubation. An endobronchial tube is chosen instead of a standard double-lumen tube because the double lumen tube is too bulky to permit tracheal surgery. As discussed above, the long, flexible tube, now available from Fuji systems, is of small diameter but sufficient length (>31 cm) to reach the bronchus (see Table 1). Note that the tip design in endobronchial tubes is important. There is no long segment of bronchus for the cuff and distal portion to sit in, so a shorter cuff-to-end design is preferable. Trimming the end of an endotracheal tube will make the cuff incompetent because the cuff air channel runs beyond the cuff. The endobronchial tube is positioned under fiber-optic guidance; however, frequent tube malpositioning occurs because of surgical manipulation as well as the flexible design of the tube.

With endobronchial intubation, 1 lung will not be ventilated, and the degree of shunt and desaturation is variable.^17-19 A full discussion of hypoxia and shunt physiology in 1-lung ventilation is beyond the scope of this article; however, standard management of hypoxia during 1-lung ventilation includes suctioning, confirming the position of the endotracheal tube by fiber-optic bronchoscopy, increasing FiO₂, and varying the ventilatory patterns. Please see Appendix C for further discussion of single-lung ventilation. Unlike a typical lung resection, it is not as easy to administer ventilation to the deflated lung. While the airway is intact, deflating the endobronchial cuff, blocking the mouth and nose, and delivering longer, larger tidal volumes can help. Alternatively, placing another endotracheal tube high in the trachea can allow differential ventilation or at least constant positive airway pressure (CPAP). Another approach is to place an LMA after the endobronchial tube, and if it seals sufficiently, CPAP can be administered. Finally, a jet catheter can be placed in the trachea. Indeed, a technique using 2 jet catheters has been described.²⁰ The jet catheter has the advantage of not requiring a seal but may not be effective if there is substantial distal obstruction. In extreme circumstances, blood flow to the pulmonary artery can be restricted, lessening shunt.

Once the airway is open, CPAP cannot be administered from above. A second tube can be placed from the field into the deflated lung, or a jet catheter can be used. The jet catheter has the advantage that it is small enough to allow surgery to proceed; it does not require an entire circuit, and the length that needs to be placed in the trachea is very small. Because large tidal volumes are not needed on the surgical side, low driving pressures are possible. In the conduct of 1-lung ventilation for carinal surgery, all the considerations for conventional pulmonary resection should be taken into account. Care with airway pressures and avoidance of overdistention is important. In cases where a pneumonectomy is performed, there are also the issues of thoracic volume and shift of the mediastinum as well as the need for careful fluid management, lower FiO₂, and gentle surgical manipulation.^21,22

Emergence from anesthesia in carinal surgery is very similar in nature to that in tracheal surgery, and all the same precautions should be used. Cord swelling is less likely, but obstruction from blood and secretions are more common. Pain control will be a bigger factor, so selection of techniques that do not suppress respiratory drive is preferable. The patient should be monitored in the intensive care unit postoperatively.

Patients with previous carinal surgery who present for unrelated surgery should not, in general, present particular anesthetic problems. It would be prudent to avoid pushing an endotracheal tube too distal and risk injuring an anastomosis. Most anesthesiologists at centers with experience with these patients would confirm good tube position and an undamaged distal airway with bronchoscopy after intubation. If lung isolation is required for the surgical procedure, the considerations are more involved. As much as possible, it is wise to avoid instrumenting and especially inflating a cuff in a repaired region. The carinal anatomy will be abnormal, with possibly shorter bronchial lengths and different angles of departure for the bronchi. The use of an endobronchial tube may be necessary. In any case, all tube positioning should be done under fiber-optic guidance to avoid the risks of malpositioning.

Surgery on the Bronchus: Sleeve Resection

Sleeve resection is the resection of discrete circumferential sections of the bronchus. It has become a popular choice for centrally located, bronchi-involving pulmonary mass removal. The technique may be used for benign or malignant lesions and allows for preservation of healthy lung parenchyma. It involves dissection of the mass away from the hilum and resection of the affected part of the bronchus, with subsequent reanastomosis. It is sometimes used as an option for those with cardiopulmonary reserve insufficient for pneumonectomy. Sleeve resection can be performed via thoracotomy or video-assisted thoracoscopic surgery, though the former is more common. If there is invasion of the surrounding large vessels, then vascular reconstruction may be performed as well. The sleeve can also be extended to involve more than 1 lobe if needed.²³

Initial diagnosis of bronchial masses is generally via radiographic imaging. By the time the patient comes to the operating theater for resection, the disease process has usually been confirmed by histopathological evaluation. Often, it is a cancerous etiology. As part of further evaluation for operative intervention, the patient may have undergone pulmonary function studies, lung ventilation/perfusion scanning, and possibly VO_2max testing.

During preoperative evaluation, medical issues specific to cancer patients should be considered, including implications from any previous chemotherapy or radiation, metabolic effects of paraneoplastic syndromes, location of and physiological derangement from metastatic lesions, and mass effects from the tumor itself. Mass effects can include tracheal anatomical distortion (airway management concern), superior vena cava syndrome, recurrent laryngeal nerve palsies, and phrenic nerve palsies.²⁴ As discussed in the previous section, PFTs may be useful in predicting the degree of hypoxia on initiation of 1-lung ventilation and should be carried out prior to surgery.³ The biggest utility in PFT testing including V/Q scanning is to establish if adequate lung function will remain following surgical resection and predict long-term outcomes caused by respiratory morbidity.^3,25 Informed consent should include a discussion about transfusion, adequate intravenous access, arterial monitoring, and postoperative pain control. Coordinated planning should be carried out with the surgical team and based on planned operative procedure. The surgical approach to sleeve resections is discussed in detail in an accompanying article by Yu and Weyant.²⁶ If an open approach is planned, a thoracic epidural should be offered to help control postoperative pain. If the procedure is to be done by video-assisted thoracoscopic surgery, one could consider paravertebral blocks.

Anesthetic induction can be safely managed using standard induction agents, unless there is significant airway obstruction from the mass. Airway management is conventionally 1-lung ventilation. Additional maneuvers for management of hypoxia in this setting include differential ventilation, jet ventilation of the operative lung, and vascular clamping as noted above. Note that CPAP to the operative lung is not an option for maintenance of oxygenation when the bronchus is open. Selective jet ventilation of bronchi not involved in the sleeve resection has been performed successfully.²⁷ Maintenance may be with inhaled anesthetic or intravenous anesthesia. An epidural catheter, if present, should be dosed prior to emergence. Emergence generally involves extubation in the operating room. Postoperative care should involve the intensive care unit.

Postthoracotomy Pain

Though the complexities of postoperative pain manin thoracotomy patients is beyond the scope of this article, pain management does deserve a brief discus Chronic postthoracotomy pain is defined as constant or intermittent pain along the thoracotomy scar line greater than 2 months after surgery. A recent review sugthe rate of chronic postthoracotomy pain to be 30% to 50%.²⁸ There have been multiple studies suggesting that chronic postthoracotomy pain has multiple etiologies. It is generally accepted that intercostal nerve injury plays a role. There are conflicting data as to whether or not generalized hyperresponsiveness plays a role.^29-31 Chronic pain has far-reaching consequences. It results in loss of work productivity, a strain on health care resources, increased cost to patients and society, decreased quality of life for patients, and increased mental health problems.³² Thoracic epidural anesthesia has been shown to decrease the rate of postthoracotomy pain syndrome, though the effect of timing of epidural dosing is unclear.²⁸ Celecoxib has been shown to improve pain control when used in conjunction with thoracic epidural after thoracotomy; however, there have been no studies to date evaluating the efficacy of Celebrex in the prevention of postthoracotomy pain syndrome.²⁸

Conclusions

Surgical intervention on the airway poses multiple challenges for anesthesiologists, surgeons, and intensivists, with different concerns for different parts of the airway. A detailed understanding of the surgical plan will help develop appropriate airway management strategies as well as intraoperative and postoperative management strategies. In addition, a thorough understanding of the pathophysiology that accompanies these unique medical conditions facilitates perioperative care and ensures best practice. Comfort with multiple approaches to airway management in these procedures is key because, often, the original plan may not work for reasons associated with anatomical abnormalities. Communication with the surgical team throughout the case is essential for a successful operation and optimal patient care.

Footnotes

Appendix A: Cross-field Ventilation

Cross-field ventilation involves sharing ventilation management with the surgical team. It is used in situations where the trachea is interrupted, and ventilation therefore cannot be achieved from above. A sterile circuit and CO₂ line are passed from the surgical field, over the drapes, to the anesthesiologist. It is important to test the integrity of the sterile circuit prior to depending on it, as one would do for our standard circuit prior to induction. The sterile circuit is placed in the airway by the surgeons, and ventilation is managed by the anesthesiologist. Often, with this type of ventilation strategy, the sterile endotracheal tube is actually in the surgical site and obstructs the repair, so ventilation is intermittent. This requires strong communication between the surgical and anesthesia teams. The endotracheal tube is removed, and surgery proceeds under apnea until the pulse oximeter indicates desaturation, at which time the surgery is paused, the surgical team replaces the endotracheal tube, and ventilation is resumed. This pattern progresses until the repair is complete.

Appendix B: Intermittent Apnea

Intermittent apnea can be a valuable tool when the surgical field involves the airway. It can be used with cross-field ventilation as discussed above or with conventional ventilation from above. It is quite useful during posterior splinting tracheoplasty. This tool is limited by the individual patient’s functional residual capacity, diffusion capacity, baseline oxygenation, oxygen delivery, and oxygen consumption. Time to hypoxemia can be lengthened by apneic insufflation.³³

Individuals who have conditions that cause chronic baseline hypoxemia would not be a good choice for this ventilation strategy because their time to hypoxemia may not be long enough for adequate surgical intervention. Additionally, patients who cannot tolerate periods of hypoxia, such as those with significant coronary artery disease, should be excluded from this ventilation strategy. Obesity is not an absolute contraindication to intermittent apnea. Apneic insufflation prolongs time to hypoxia in obese patients.³⁴ Obese patients will simply have a smaller functional residual capacity. As with cross-field ventilation, strong communication with the surgical team is essential.

Appendix C: Single-Lung Ventilation

Single-lung ventilation is another option for oxygenation and ventilation during airway procedures. Lung isolation assists surgical exposure in operations such as carinal and sleeve resections. Other indications for single-lung ventilation include pulmonary hemorrhage, preventing spillage of infected contents from 1 lung to another, and bronchopleural fistula. A lung may be isolated by a double-lumen tube, a single-lumen tube guided into a mainstem bronchus, or a bronchial blocker.

Single-lung ventilation can be challenging from the standpoint of both oxygenation and ventilation. Keys to successful management include identifying those at risk for hypoxemia, minimizing intrapulmonary shunting, and calculating a rough estimate of how much hypoxemia that individual’s physiology will allow. Right-sided operations, supine positioning, baseline hypoxemia, and more perfusion to the nonventilated lung are all risks for hypoxemia.³⁵ Controversy exists as to whether obstructive lung disease is protective or harmful in 1-lung ventilation. Factors related to tolerance of hypoxemia include cardiac output, hemoglobin concentration, and oxygen consumption. If, based on the above-mentioned factors, you surmise that the patient is at risk for significant hypoxemia during 1-lung ventilation, then a modified 1-lung strategy should be discussed with the surgeon prior to induction.

In general, during single-lung ventilation, the goal should be to minimize the shunt fraction. This can most easily be divided into controlling ventilation and controlling perfusion. Controlling ventilation starts with ensuring proper positioning of whatever airway device you are using. The rest focuses on avoiding/decreasing atelectasis in the dependent lung while avoiding overdistention and therefore increasing shunt by collapsing regional capillaries. There are multiple strategies to consider. Large tidal volume strategies probably do not improve oxygenation. Moderate tidal volume strategies may result in less barotrauma. The decision to use positive end-expiratory pressure (PEEP) should be based on each individual situation. If the patient has intrinsic PEEP (based on their physiology, the ventilation strategy, or both), then further PEEP may not be beneficial. One should also consider FiO₂ in a ventilation strategy. An FiO₂ of 100% may increase atelectasis via absorption.³⁵

There are limited ways in which an anesthesiologist can control differential lung perfusion. Overall, our anesthetic choice does not seem to play a role in clinically relevant hypoxemia during 1-lung ventilation. There are some studies showing the combination of almitrine and nitric oxide can improve PaO₂ during 1-lung ventilation; however, this is not recommended as an early intervention because of toxicity concerns. Increasing hemoglobin concentration in those who are anemic may decrease the shunt fraction.³⁵

Hypoxemia during single-lung ventilation needs to be addressed by simultaneously correcting the hypoxemia and finding the cause. Clinical reasoning should be applied, and if the patient is quickly progressing to an unsafe state, then 2-lung ventilation should be resumed. If there is time, then the following steps may be taken. First, if possible, increase the FiO₂. One can also apply PEEP to the ventilated lung or increase the current PEEP if applicable. The position of the endotracheal tube should always be investigated, and the tube should be repositioned if appropriate. Suctioning of airway secretions may be beneficial. Recruitment maneuvers can also be applied to the ventilated lung. If these measures fail and the patient has reached an intolerable level of hypoxemia, then 2-lung ventilation should be resumed. Administration of CPAP to the operative lung can be very beneficial; however, this only works on an expanded lung. Therefore, it must be applied prior to lung collapse or after reinflation, prior to resumption of 1-lung ventilation. Jet ventilation of the operative lung has also been described.³⁵

Appendix D: Jet Ventilation

Jet ventilation involves the delivery of a gas, like oxygen, under high pressure. This technique of oxygenation can be useful in situations where a traditional endotracheal or endobronchial airway impedes surgical technique. Jet ventilation may be delivered through supraglottic, infraglottic, or transtracheal routes.³⁶ It is not generally used for lengthy surgical procedures. The delivery system may be high or low frequency. High-frequency jet ventilation may be delivered via an automated device with a ventilation frequency up to 150 cycles/min, whereas low-frequency ventilation is either an automatic or a manual technique, delivered at around 20 cycles/min. Gas inflow and egress during jet ventilation depend on driving pressure, ventilation frequency, and inspiration duration. Driving pressure is the pressure generated from the external gas source. It is part of what controls insufflation volumes. Note that the relationship of driving pressure and insufflation volume is not linear.³⁶ Inspiration duration is the amount of time spent in insufflation. Longer inspiration duration leads to larger delivered volumes at the cost of shorter passive exhalation time. This can result in overinflation of the lungs and decreased carbon dioxide elimination. Inspiration duration ratio is generally set at 50%. The number of cycles generated per second is referred to as the ventilation frequency. Higher frequencies with unchanged working pressure and inspiratory duration result in smaller delivered gas volumes, increased dead space ventilation, decreased carbon dioxide removal, and increased airway pressures from auto-PEEP.³⁶ For high-frequency jet ventilation with an automated device, Biro³⁶ suggests beginning settings at working pressures of 1.6 bar, a frequency of 150 cycles/min, and an inspiratory to expiratory ratio of 1:1. Manual jet ventilation is usually low frequency; 20 cycles/min with a working pressure of less than 0.8 bar is suggested by Biro.³⁶

Hypoxia during jet ventilation is generally acute or slowly progressive. Acute hypoxia is generally secondary to barotrauma induced pneumothorax and should be treated with a chest tube and alternative mode of ventilation. Slowly progressive hypoxia is likely a result of insufficient gas exchange.³⁶ Steps to improve oxygenation include increasing the FiO₂, increasing the working pressure, and extending the inspiration duration.³⁶ If the above measures fail, conventional ventilation should be instituted. Note that the FiO₂ received by the patient is never as high as what is delivered because there is entrainment of ambient air. Hypercapnia can also be a problem with jet ventilation. Increasing driving pressure may improve carbon dioxide elimination. The maximum working pressure is around 4.5 bar.³⁶ Monitoring end-tidal carbon dioxide concentrations is not possible at high frequencies and may be awkward to arrange at lower frequencies; thus, arterial blood gas monitoring is helpful. Biro suggests that a carbon dioxide level of 1.5 times baseline is acceptable.³⁶

Complications of jet ventilation include barotrauma (pneumothorax, pneumopericardium, etc), necrotizing tracheobronchitis, gastric insufflation with resultant trauma, and dysrhythmias.³⁷ It can be difficult to maintain adequate oxygenation and ventilation during jet ventilation in patients with a stiff thorax, advanced obstructive or restrictive lung disease, decreased diffusion capacity, and obesity. Hypothermia should also be a concern. If the jet location entrains much ambient gas, even built-in systems for heating and humidifying gas will be ineffective. It has been fund that 15 minutes of jet ventilation with unwarmed air can lead to a drop in body temperature of 2°C.³⁶

Author Note:

This article was subjected to a two-tier, blind review process that did not involve any of the contributing authors who are currently members of the editorial board.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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