Once IV access is established and monitors have been applied, premedications can be administered to the patient in preparation for bronchial thermoplasty. Preprocedure medications are outlined in Table 2. If the patient has not taken their prescribed oral prednisone on the day of the procedure, premedication should include IV administration of methylprednisolone or its equivalent. Albuterol and an antisialogogue agent such as glycopyrrolate should be administered a minimum of 30 minutes before the procedure. As an alternative to glycopyrrolate, atropine may be used. Caution should be used with these agents due to their chronotropic risks and physicians should consider their individual institutional guidelines regarding which drugs may be given intravenously. Glycopyrrolate is preferred over atropine because it is a superior drying agent with fewer propensities for adverse central nervous system effects or tachyarrhythmias. Glycopyrrolate administered IV reduces airway secretions much faster (approximately 5 min) than with an IM route (approximately 30 to 60 min). Properly treating the patient with an effective drying agent is important in bronchial thermoplasty as it reduces the amount of airway secretions and may improve visibility through the bronchoscope. Though perhaps not clinically proven to have a meaningful effect in improving topical anesthesia in other bronchoscopic procedures,13 the authors have experienced the benefits of an effective drying agent in bronchial thermoplasty.7–9 Additionally, the physician may give midazolam for anxiolysis while the patient is on the monitor with supplemental oxygen. The goal is to relax the patient in preparation for topical anesthesia of the airway.
Supraglottic Topical Anesthesia
Bronchial thermoplasty is performed with a bronchoscope either through an oral or nasal approach, with the majority of cases done via a nasal approach because patients seem to have less gagging and fewer secretions. Application of topical anesthesia may start with 5 mL of 1% lidocaine jelly applied to the nostril being used for inserting the bronchoscope. The physician may use more or less to achieve the end point, which is an anesthetized and lubricated nasal passage. Using 1% lidocaine allows the bronchoscopist to have more local anesthetic available for topicalizing the bronchial tree. If there are concerns with epistaxis, phenylephrine or oxymetazoline spray or topical cocaine may be used.
The next step is for the bronchoscopist to adequately anesthetize the hypopharynx. An approach that is easy and effective is to have the patient gargle with 5 mL of 2% lidocaine and then expectorate. This limits the systemic absorption of lidocaine and decreases the likelihood of toxicity. Another option is to aerosolize the posterior pharynx with 1% to 2% lidocaine. Regardless of technique, the goal is to anesthetize the patient's posterior pharynx to significantly diminish or eliminate the patient's gag reflex.
Vocal Cord and Subglottic Topical Anesthesia
Once the patient's upper airway has been sufficiently anesthetized, application of topical anesthesia to the vocal cords and bronchial tree can proceed. Although different concentrations of lidocaine may be used, 1% lidocaine is recommended to limit the potential for lidocaine toxicity. At the vocal cord level, 1% lidocaine can be applied in small (2 mL) aliquots until the patient seems comfortable with minimal coughing. After vocal cord topical anesthesia, the patient's sedation level is reassessed and considerations are made for supplementing with more anxiolytic or antitussive medications (see Sedation section) as needed. As the bronchoscopist proceeds down the airway, 1% lidocaine should be used in small (0.5 to 2 mL) aliquots down the bronchial tree. The bronchoscopist should apply the local anesthetic, focusing more attention on the airway segments being targeted for treatment. After 30 to 40 minutes into the procedure, the bronchoscopist may consider application of additional topical anesthesia if necessary.
The maximum dose of lidocaine is often institution specific; however, 600 mg or 8.2 mg/kg of lidocaine or less has been used safely in asthmatics undergoing bronchoscopy.14 The patient should be continuously monitored for signs and symptoms of lidocaine toxicity. Toxic reactions to local anesthetics most frequently involve the central nervous system and may include: lightheadedness, tongue numbness, visual changes, auditory disturbances, seizures, or loss of consciousness.15 If doses exceed the maximum limits, consider monitoring lidocaine levels postprocedure.
Once the patient's airway is adequately anesthetized it is critically important to achieve or maintain an optimal level of sedation. Most patients can undergo bronchial thermoplasty under moderate or conscious sedation. It is recommended that institutional sedation guidelines are followed. The American Society of Anesthesiologists (ASA) provides the following definitions for various levels of sedation that are recognized by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO)16:
- Minimal sedation (anxiolysis) is when a patient responds normally to verbal commands;
- Moderate sedation (formerly conscious sedation) is when a patient responds purposefully to either verbal commands alone or with light tactile stimulation;
- Deep sedation is when a patient cannot be easily aroused but responds purposefully with repeated or painful stimulation. Cardiovascular function is usually maintained.
Sedation is a continuum and health care providers intending to induce a given level of sedation need to closely observe the patient and have the skills necessary to support patients whose sedation becomes deeper than intended.
Sedation is generally achieved using a combination of a short acting benzodiazepine and a narcotic. The authors suggest that the optimal combination is midazolam and fentanyl, but other medications can be used. Midazolam is a fast acting benzodiazepine with a short half-life, and it can be easily titrated to effect. It is often initially given in a 1 to 2-mg loading dose followed by incremental doses of 0.5 to 1 mg as needed. The onset of the effect is within 1 to 3 minutes, with a maximum duration of about 2 hours. Midazolam also produces antegrade amnesia, anxiolysis, and has an anticonvulsant effect. The objective is patient anxiolysis and patient comfort while still maintaining adequate spontaneous ventilation during the procedure. The typical dose range for midazolam during bronchial thermoplasty is 2 to 10-mg IV. Supplemental doses should be given if the patient is anxious or has minimal sedation assuming adequate oxygenation and ventilation. The precise timing of sedation will vary between patients and largely depends upon the clinical judgment of the physician.
Fentanyl is also an effective sedating agent used during bronchial thermoplasty and it is beneficial because it has both potent analgesic and antitussive properties. An effective loading dose is 50 to 100-μg IV with additional doses of 25 to 50-μg IV as needed. Onset of action is 2 to 4 minutes with a peak effect at 10 to 15 minutes and duration ranging from 30 to 60 minutes. Supplemental doses should be administered if the patient has minimal sedation, is having pain, or coughing excessively. The typical dose range for fentanyl during bronchial thermoplasty is 50 to 300-μg IV. The ultimate objective is to provide the patient with adequate analgesia and sedation with minimal coughing.
It is important to note that benzodiazepines and opiates have different mechanisms of action, but potentiate each other's actions including respiratory depression and hypotension. Therefore, frequent smaller supplemental sedative/analgesic doses allow for more effective titration. When fentanyl and midazolam are used together in low incremental doses titrated to effect, excellent sedation can be produced while avoiding side effects. The main advantage of using midazolam and fentanyl to induce moderate sedation are their fast onset times, which make them more easily titratable. In addition, both medications have reversal agents (naloxone and flumazenil, respectively) that can be used to antagonize their effects if necessary.
The use of prophylactic antiemetics can be considered when performing bronchial thermoplasty under moderate sedation, especially when opiate drugs are used. Agents such as fentanyl can significantly contribute to postprocedure nausea, which is unpleasant for the patient and leads to longer recovery times. Antiemetics to be considered may include ondansetron, metoclopramide, promethazine, or dexamethasone. Giving an antiemetic is especially important in patients with motion sickness or with a history of postoperative nausea. The addition of antiemetics can make patients more comfortable and tolerant of additional procedures by minimizing any nausea they may experience. The complete patient management protocol is summarized in Table 2.
Postprocedure care should follow appropriate institutional guidelines, and it is recommended that patients should be carefully monitored and discharged only after they are deemed to be stable and have adequate (comparable to preprocedure) lung function, mental status, and are able to take liquids adequately. Immediate postprocedure follow-up should include assessment of gag reflex, vital signs, breath sounds, and spirometry to assess FEV1. A listing of recommended postprocedure assessments is provided in Table 4.
As with any bronchoscopic procedure, there is an expected increase and worsening of respiratory-related symptoms in the period immediately after bronchial thermoplasty, such as breathlessness, wheeze, cough, chest discomfort, night awakenings, and productive cough.5,7 These symptoms typically present within 1 week of bronchoscopy and resolve with standard medical care on average within 1 week. Therefore, it is recommended that the patient be contacted 24 hours, 48 hours, and 7 days postprocedure to assess their status after the bronchoscopy. In particular, there is also a potential for excess mucus production in response to bronchoscopy and bronchial thermoplasty in asthma patients. It is expected that coughing will clear any excess mucus; however, it is possible that the mucus may become thickened and occlude the airway. In the event thickened mucus is suspected, a chest radiograph should be obtained and, if mucus plugging is confirmed, patients should be treated with chest physiotherapy and/or therapeutic bronchoscopy as indicated. They should also be monitored carefully until resolution occurs. In considering the potential long-term role for bronchial thermoplasty in the treatment of asthma, the short-term risk of increased respiratory-related symptoms should be weighed against the potential for improvement in asthma control.
Bronchial thermoplasty delivered with the Alair Bronchial Thermoplasty System is an investigational procedure designed to reduce the amount of airway smooth muscle1 and hence the potential for bronchospasm and asthma symptoms. In an unblinded, multicenter, randomized clinical trial involving patients with asthma, bronchial thermoplasty was shown to improve asthma control and quality of life.7 Although the potential for a strong placebo effect exists in this unblinded study, the magnitude and persistence of the effects observed were likely greater than what could be attributed to placebo alone.
Successful bronchial thermoplasty requires that all accessible airways distal to the mainstem bronchi between 3 and 10 mm in diameter, with the exception of the right middle lobe, be treated once and only once. To achieve this goal, a systematic approach moving from distal to proximal within an airway and working methodically from airway to airway across the region of lung being treated is recommended. This systematic approach results in a bronchoscopy that is generally longer in duration than bronchoscopies performed for bronchoalveolar lavage or tissue biopsy. Excellent patient management during bronchial thermoplasty must be emphasized because optimal administration of the treatment requires minimal patient movement during the procedure. Thus, adequate and effective administration of sedatives and analgesics to achieve and maintain moderate sedation is critically important. Because the full treatment of the entire lung requires more than one bronchoscopy session, it is important that patient comfort is maximized so that the patient's anxiety for future bronchoscopies is minimized.
The choice of medications necessary for good patient management will ultimately be the choice of the physician performing the procedure and may vary based on country or institution-specific guidelines and practices. However, midazolam and fentanyl are currently recommended and are excellent choices because of their familiarity, ability to be carefully titrated, and if necessary, to be rapidly reversed. In the future, the use of other sedative/hypnotics such as propofol during bronchial thermoplasty may prove to be advantageous.17 The efficient initial induction and subsequent clearance of propofol from the plasma with minimal central nervous system effects is especially useful for outpatient procedures like bronchial thermoplasty. The use of propofol would likely reduce the postprocedure recovery time for patients. However, administration of propofol by someone other than an anesthesiologist remains controversial and its acceptance for use in the United States currently varies by hospital and also by state.
Current sedation guidelines (as adopted by JCAHO from the ASA definitions) acknowledge the sedation continuum and include the concept of rescue. Physicians administering moderate sedation should have the skills and equipment necessary to “rescue” a patient from unintended deep sedation. Practitioners should consider the sedation and procedure guidelines at their particular institution.
Bronchial thermoplasty is a complex procedure that requires considerable expertise in flexible bronchoscopy, and a systematic approach to ensure that all accessible airways are identified and treated properly. Bronchoscopists should perform bronchial thermoplasty in a supervised setting to establish basic competency in patients with asthma and to become comfortable with the intricacies of the procedure. The authors of this manuscript were trained by the manufacturer of the Alair Bronchial Thermoplasty System before participating in the clinical study. Individual institutions will ultimately decide on the competency of each bronchoscopist interested in performing bronchial thermoplasty.
Preliminary clinical results of bronchial thermoplasty seem encouraging,5,7 although these findings should be interpreted with caution, as these were unblinded studies of a procedure with a high potential for placebo effect. An appropriately powered, blinded, sham-controlled study is currently underway to assess the ultimate risk to benefit ratio of this procedure.
In conclusion, bronchoscopy experience, careful patient selection, patient management during the procedure and appropriate postprocedure follow-up should all be considered for bronchial thermoplasty to be safe and to achieve the best possible outcomes.
The authors are indebted to Gerard Cox, MB and John Miller, MD (McMaster University, Hamilton, Canada) for pioneering bronchial thermoplasty for the treatment of patients with asthma and to the AIR and RISA Trial Study Groups for their important contributions to the advancement of bronchial thermoplasty.
The Alair Bronchial Thermoplasty System has received a CE Mark to sell the device in the European Union and it is currently under investigation in a FDA approved IDE pivotal clinical trial in the United States (www.clinicaltrials.gov/ct/show/NCT00231114?order=1).
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Keywords:© 2007 Lippincott Williams & Wilkins, Inc.
bronchial thermoplasty; asthma; airway smooth muscle; bronchoscopy; radiofrequency energy; patient management; conscious sedation