Anesthesia in the Bronchoscopy Suite

Endobronchial Ultrasound with Transbronchial Needle Aspiration

Endobronchial ultrasound with transbronchial needle aspiration (EBUS-TBNA) is a less invasive procedure than traditional mediastinoscopy; both are intended to yield tissue for diagnostic purposes. For EBUS, an ultrasound transducer integrated into a dedicated bronchoscope is placed either directly in contact with the tracheal or bronchial wall or indirectly via a saline-inflated balloon, displaying real-time ultrasound images. Fine needle aspiration of lymph nodes can then be performed under ultrasound visualization. Procedural indications include staging of non–small cell lung cancer, diagnosis of suspected lung cancer without endobronchial lesions, and evaluation of unexplained mediastinal lymphadenopathy. EBUS-TBNA may be diagnostically superior to computed tomography (CT) and positron emission tomography (PET) and has overall accuracy similar to that of mediastinoscopy but with less invasiveness and the ability to sample hilar lymph nodes. As the required technology is maturing and becoming more widely available, EBUS-TBNA is quickly becoming the standard of care.

EBUS with or without biopsies is usually only minimally stimulating, and most procedures can be completed under conscious sedation; however, general anesthesia may be requested in several instances. First, sampling adequacy is improved with sampling a higher number of lymph node stations. When extensive staging is performed, particularly when lymph nodes are less than 1 cm in their largest dimension, procedures can become quite prolonged. Patient intolerance may necessitate general anesthesia. Further, some pulmonologists prefer general anesthesia when a large number of stations are sampled, believing it improves diagnostic yield. Finally, the saline-filled balloon can occasionally completely obstruct the airway; cases have been reported in which coughing against the obstruction led to negative-pressure pulmonary edema, a problem obviated by general anesthesia with muscle relaxation.

Electromagnetic Navigational Bronchoscopy

Electromagnetic navigational bronchoscopy (ENB) was developed as a guidance system to assist the bronchoscopist in performing a biopsy of difficult-to-access peripheral, pulmonary nodules. The technology combines multidirectional CT (MDCT) imaging, magnetic field localization, and a steerable probe with a magnetized tip. During the procedure, the bronchoscope is guided into the area of interest and the tip location is displayed on the MDCT image. Diagnostic yield of biopsies for small peripheral lung nodules is much improved over previous techniques. Other potential uses include placement of fiducial markers for stereotactic radiotherapy and marking of nodules for surgical wedge resection. Sedation and anesthetic needs are similar to those of EBUS and dictated by patient comorbidities, needs of the bronchoscopist, and anticipated procedure duration.

Treatment of Central Airway Obstruction

In modern practice, relief of obstruction of the central airways (trachea, mainstem bronchi, and bronchus intermedius) remains the main indication for therapeutic bronchoscopy. Obstruction can result from intraluminal malignancy, external compression by mediastinal mass, massive hemoptysis with clot, or benign causes such as foreign body, postintubation tracheal stenosis, or tracheobronchomalacia. A variety of therapeutic approaches exist, with selection depending on cause, urgency, and availability. Laser ablation, electrocautery, argon plasma coagulation (APC), mechanical debridement, and airway stents can provide immediate relief of obstruction. In contrast, cryotherapy, brachytherapy, and photodynamic therapy produce delayed effects. If intervention is urgent because of severe or progressive obstruction, effort should be made to stabilize the patient to enable completion of diagnostic studies (such as CT imaging) to aid in developing an optimal treatment strategy. In this situation, heliox, given its lower density than air or 100% oxygen, can improve gas flow across highly narrowed areas of the airway and reduce turbulent flow conditions. If heliox is ineffective or not available, consideration must be given for intubation distal to the obstruction, typically accomplished with fiberoptic bronchoscopy. Alternatively, rigid bronchoscopy in expert hands can be lifesaving.

The neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and other “hot” therapies, such as electrocautery and APC, are designed to vaporize tissue and achieve superior coagulation and thus are often chosen to treat obstructing central airway lesions. Unfortunately, these thermal techniques also carry an increased risk for airway and procedure room fires. Microdebriders, which mechanically debulk airway tumors, were developed as “cold” therapies that still can rapidly open an airway. Although inferior to thermal techniques in controlling bleeding, microdebriders also avoid some of their potential complications.

APC is based on gas flow, and many lasers have a gas-cooled fiber that is used to apply the energy. Case reports have documented intravascular gas during use of the Nd:YAG laser and even cardiac arrest secondary to gas embolism during bronchoscopic APC. In animal studies, gas emboli were more frequent with higher laser coolant flow and longer laser pulse generation, a finding the authors speculatively ascribed to positive-pressure ventilation forcing air through small bronchovascular defects. Therefore current procedural recommendations include using the lowest possible setting for laser coolant flow, using noncontact mode, and applying thermal ablation only during apnea or spontaneous breathing.

Airway Stents

Indications for airway stenting include extrinsic airway compression, mixed extrinsic and endoluminal lesions, recurrence of airway compromise after treatment of intraluminal lesions, inoperable nonmalignant disease, and treatment of airway fistulas. Stents can be made of silicone, expandable metal, or a combination of both, such as a covered metal stent. Metal stents resist migration because they become embedded in airway tissue and tend to generate a proliferative granulation response. Unfortunately, this also means that metal stents can be difficult and potentially dangerous to remove if in place for more than a few weeks. Expandable metal stents can be placed via flexible or rigid bronchoscope. Fluoroscopy is often used to guide placement. Because silicone stents do not collapse, a rigid bronchoscope must be used for placement.

Complications are common with all stent types. Granulation tissue formed after metal stent placement may occasionally cause airway obstruction and necessitate reintervention, often by Nd:YAG laser ablation. Removal of metal stents is best accomplished with a rigid bronchoscope and jet ventilation. Silicone stents are much easier to remove but are prone to migration, mucous obstruction, and infection.

Bronchoscopic Balloon Dilatation

Bronchoscopic balloon dilatation is commonly used to treat nontraumatic subglottic stenosis, often in conjunction with injection of corticosteroids or the anti-neoplastic drug mitomycin-C in an attempt to reduce the rate of restenosis. Total intravenous anesthesia (TIVA) with paralysis is often used in combination with intermittent bag-mask ventilation or jet ventilation before and after balloon dilatation, which typically lasts 1 to 3 minutes and can be performed repeatedly during a single procedure. During balloon dilatation, it is important to maintain adequate muscle relaxation and monitor for diaphragmatic firing to prevent respiratory effort against the occluded airway and the subsequent development of negative-pressure pulmonary edema. Further, improvement in stenosis is often delayed, so the anesthesia provider must be particularly vigilant in monitoring for airway obstruction and adequate ventilation both immediately after the procedure and in the postanesthesia care unit (PACU).

Radiofrequency Ablation

Radiofrequency ablation (RFA) is a minimally invasive treatment modality that has previously been used to treat patients with hepatic, renal, and breast tumors. After the RFA electrode is inserted into the target lesion, alternating radiofrequency currents are generated, leading to frictional heating and ultimately coagulative necrosis and cell death. The procedure tends to be well tolerated and is often done under conscious sedation. However, achieving effective targeting of pulmonary neoplastic lesions and protecting nontargeted tissues can be challenging. Deflating the target lung can be helpful but may move the lesion too close to central structures. A technique to obtain improved tumor positioning has been described using lung isolation with a double-lumen endotracheal tube (DLT) with static inflation of the target lung by either clamping the DLT lumen supplying the target lung or applying CPAP to maintain target lung inflation. Although not reported with RFA of pulmonary lesions, the use of high oxygen concentrations may pose a fire risk.

Bronchial Thermoplasty

In poorly controlled chronic asthma, airway smooth muscle hypertrophy is a component of airway remodeling, which contributes to ongoing symptoms. Bronchial thermoplasty, which uses heat generated by radiofrequency energy to destroy bronchial smooth muscle, has been shown in at least two trials to (1) improve prebronchodilator forced expiratory volume in 1 second (FEV ₁ ), (2) reduce severe exacerbations, (3) decrease rescue medication use, and (4) improve reported quality of life for patients with severe asthma. Current guidelines, however, limit bronchial thermoplasty as a treatment option to selected patients with severe persistent asthma already on maximal medical therapy. Bronchial thermoplasty is generally well tolerated and can usually be accomplished under conscious sedation. However, if the anesthesiologist is involved, he or she must be aware of the increased risk for respiratory complications in the first 24 hours after the procedure, primarily acute bronchospasm or increased mucous plugging, occasionally resulting in lobar collapse.

Bronchoscopic Lung Volume Reduction

The National Emphysema Treatment Trial was published in 2003, demonstrating that in a carefully selected patient population with severe heterogeneous emphysema, lung volume reduction surgery (LVRS) reduced mortality, improved exercise tolerance, and improved quality of life. However, LVRS was associated with considerable morbidity and mortality, causing investigators to speculate that less invasive bronchoscopic interventions might achieve similar benefits while minimizing perioperative risk. Multiple techniques are currently under study, including intrabronchial valves, lung volume reduction coils, lung sealant, and bronchoscopic thermal vapor ablation. The goal for any of these procedures is to achieve segmental or lobar collapse to effectively reduce lung volume, thus reducing air trapping and improving elastic recoil and expiratory flows. Although results for many of these modalities are somewhat promising, none are ready for widespread adoption, and optimal anesthetic techniques have not yet been described.

History and Review of Systems

The majority of patients presenting for interventional bronchoscopic procedures are classified as American Society of Anesthesiologists physical status 3 or higher. Tobacco abuse is a common risk factor for the majority of upper airway and pulmonary pathological conditions necessitating bronchoscopic intervention. Unsurprisingly, smoking-related diseases such as obstructive or less commonly restrictive pulmonary disease, coronary artery disease, congestive heart failure, peripheral vascular disease, cerebral ischemic disease, hypertension, malnutrition, and malignancies outside the lungs and airway are extremely common in this population. Heavy alcohol use, type 2 diabetes mellitus, and obesity are also common. Sequelae of the aforementioned pathological conditions that can affect anesthetic management include chronic kidney disease, obstructive sleep apnea, gastroparesis and gastroesophageal reflux disease, and limited neck mobility. The review of systems should further focus on the patient’s functional status, symptom control of baseline pulmonary or cardiac disease and any environmental triggers, presence of orthopnea, specific triggers for cough, and the severity of reflux disease.

Rigid bronchoscopy requires neck hyperextension, so patients presenting for this procedure should be assessed for risk factors for cervical spine subluxation such as trisomy 21 (Down syndrome) cervical ankylosis, or rheumatoid or other inflammatory arthritis with cervical involvement. Inquiring about previous chemotherapy is important, particularly the use of bleomycin and its associated risks for pulmonary fibrosis and acute oxygen toxicity, as well as doxorubicin and its potential for causing cardiomyopathy. Patients with previous lung transplantation or cystic fibrosis require increased sedative dosing during flexible bronchoscopy. Interestingly, advanced age alone does not confer an increased risk for complications from either flexible or rigid bronchoscopy.

Preprocedure Studies

Patients with suspected chronic obstructive pulmonary disease (COPD) should undergo spirometry and also should have a baseline arterial blood gas sample drawn if COPD is determined to be severe (FEV ₁ <40% predicted and/or room air oxygen saturation [Sa o ₂ ] <93%). If biopsies are to be performed, coagulation tests, including international normalized ratio, partial thromboplastin time, and platelet count, may be considered. Other laboratory studies such as a complete blood count or metabolic panel should not be routinely ordered unless prompted by the history and review of systems. Radiographic images must be reviewed, particularly when central airway obstruction is present or suspected, allowing the anesthesiologist to assess the potential for clinical airway compromise. Large bullae typical of severe emphysema suggest an increased risk for pneumothorax or other barotrauma with jet ventilation or even conventional positive-pressure ventilation.

Premedication