Flexible bronchoscopy can be performed with topical anesthesia.3 The medications used are either benzocaine and tetracaine (Cetacaine) or lidocaine (Xylocaine). Cetacaine is a combination of agents that is particularly well suited for bronchoscopy. The rapid onset of Cetacaine is attributable to the action of benzocaine, and its extended duration (typically 30–60 minutes) is owing to the action of butamben and tetracaine. Typically, only four to five sprays are used to avoid inducing methemoglobinemia. Methemoglobinemia occurs when more than 1% of the heme iron is oxidized to the ferric form. The oxidized hemoglobin (i.e., methemoglobin) is incapable of reversibly binding oxygen. Methemoglobinemia is readily treated with an infusion of methylene blue.
To perform a well-tolerated bronchoscopy, three anatomic areas need to be anesthetized: the hypopharynx, larynx, and trachea. The hypopharynx can be anesthetized directly with Cetacaine or lidocaine sprays oriented behind the tongue. Some bronchoscopists prefer to have the patient gargle with lidocaine or swallow Xylocaine jelly.
The larynx can be anesthetized using a combination of techniques. An effective initial approach is to use a nebulizer. Nebulization can deliver lidocaine to the larynx and trachea. A nebulizer connected to a pressurized oxygen source can be used to synchronize the sprays with deep inspiration. A hole cut in the oxygen tubing is occluded intermittently with a finger to produce a forceful spray. This technique facilitates the delivery of lidocaine to the larynx and the trachea. Lidocaine also can be instilled into the larynx under direct vision using the flexible bronchoscope.
The trachea typically is anesthetized with 5 mL of 1% lidocaine after the bronchoscope has passed through the vocal cords. Additional lidocaine is administered at the level of the carina and the mainstem bronchi bilaterally.
Flexible Bronchoscope Equipment
The bronchoscope consists of a handle and an insertion tube that contains the optical bundle and a working channel. The handle controls the distal segment of the insertion tube. The distal portion of the scope bends in a single 270-degree arc to facilitate examination of the entire airway. The optical bundle contains a fiberoptic light bundle and a second bundle for either digital or fiberoptic imaging. The working channel can be used to suction, pass instruments, and lavage the airways.
In the nonintubated patient, the bronchoscope is introduced either through the mouth or through the nose. Transnasal introduction is used commonly as an outpatient procedure (Fig. 61-2). This approach has the advantage of maintaining proper alignment of the bronchoscope as well as permitting the patient to comfortably swallow secretions. After proper application of topical anesthetics, the bronchoscope is gently passed through the nasal passages into the posterior pharynx.
Transnasal introduction of the bronchoscope is often used in the outpatient setting because it maintains proper alignment and permits swallowing.
In thoracic surgical patients, previously traumatized nasal passages and the presence of nasogastric tubes make oral introduction the preferred method (Fig. 61-3). The patient is asked to hold a circular bite block in his or her teeth. The bronchoscope is lubricated and the tip curved. Although the operator is looking into the open mouth – not through the bronchoscope – the lighted tip of the bronchoscope is positioned over the glottis. Holding this position in the midline, the operator then looks through the bronchoscope, and the vocal cords are visualized with minimal movements. Then 5 mL of 1% lidocaine is instilled onto the vocal cords. Note the vocal cord mobility with phonation. The bronchoscope is passed through the vocal cords, and another 5 mL of lidocaine is instilled into the trachea. Additional lidocaine may be necessary in the mainstem bronchi.
Oral introduction, the preferred method for patients with previously traumatized nasal passages or in the presence of a nasogastric tube.
The trachea should be examined for displacement of the tracheal rings or effacement of the carina. The membranous portion of the trachea should displace anteriorly during expiration and cough. In most cases it is wise to first examine the normal tracheobronchial tree to ensure complete evaluation of the airways. Each segmental orifice must be examined.
Diagnostic procedures can be complicated by bleeding and must be performed in the proper order: washings, brushings, and biopsies. Bronchoalveolar lavage is performed by centering the distal tip of the bronchoscope in a segmental orifice. A volume of normal saline, typically 50 to 150 mL, is instilled into the distal airway while maintaining occlusion of the segmental airway. The patient is asked to take several deep breaths to draw the lavage fluid into the distal airspaces. The lavage fluid then is aspirated into an appropriate container.
Brushings may be directed at either cytologic or bacteriologic diagnoses. Brushings obtained for cytology must be prepared properly to preserve cellular morphology. Similarly, distal airway brushings for bacterial culture also must be performed properly. The so-called covered brush cultures involve a covered sheath with the gelatin plug. The gelatin plug protects the brush from contamination until it is in the distal airway. The plug is expelled, and distal cultures, particularly anaerobic cultures, can be obtained reliably. If the brush is processed properly, quantitative cultures of the distal airway can be obtained.
An important development in bronchoscopy has been the use of complementary imaging techniques; that is, imaging techniques that are implemented simultaneously with the fiberoptic bronchoscopy. There are currently two commonly employed techniques: Endobronchial ultrasound (EBUS) and electromagnetic navigational bronchoscopy (ENB). EBUS is a method for imaging lymph nodes beyond the airway wall—effectively extending the potential for bronchoscopic biopsy to contiguous lymph nodes. EBUS has been associated with low complication rates and false-negative rates between 6% and 9%.4 A newer imaging modality is ENB. ENB uses spatial correlations between the patient's CT scan and a reference electromagnetic field. Computer correlation between the CT scan and the bronchoscope provides a virtual image of the airway and the surrounding lung. The imaging technology can be used to guide the bronchoscopist and permit a variety of procedures including needle biopsies and placement fiducial markers. Although the accuracy of ENB varies with surgeon experience,5 continued software improvements are likely to enhance the accuracy of ENB.
The most predictable complication of bronchoscopy is transient hypoxemia. The PaO2 routinely drops by 10 to 20 mm Hg during bronchoscopy.1,2 The relative hypoxemia is worsened by large-volume saline lavage and use of an excessive amount of suction. In most cases the predictable drop in PaO2 can be prevented with the routine use of supplemental oxygen therapy. Cardiac arrhythmias are unusual during routine bronchoscopy. Hemodynamically significant arrhythmias typically are restricted to procedures associated with hypoxia or hypercarbia. The sedation used for bronchoscopy can contribute to hypercarbia. In a patient with preexisting hypercarbia, the bronchoscopy can be performed without premedication or sedation. If the patient is likely to require high-flow oxygen or mechanical ventilation, it is advisable to intubate the patient during the procedure. A fiberoptic intubation can be performed readily by placing an endotracheal tube over the bronchoscope.
Endoscopic procedures can be associated with fever and bacteremia. Although there is no consensus regarding the use of prophylaxis in patients with artificial heart valves, most practitioners administer prophylactic antibiotics before bronchoscopy. Although transient infiltrates and fever can be observed in 5% of patients after bronchoscopy, postbronchoscopy pneumonia is rare. Proper sterile technique and bronchoscope processing will limit the life-threatening Pseudomonas pneumonia associated with a contaminated bronchoscope.