Clinical aspects of bronchoscopy

The indications for bronchoscopy are outlined in Box 156-1. A complete history and physical examination are necessary for all patients undergoing bronchoscopy for whom an anesthesia provider has been asked to assist. Concurrent medical problems increase the risks associated with the procedure; for example, patients who have a history of lung disease have an increased incidence of bronchospasm during bronchoscopy. Similarly, patients with restrictive ventilatory defects (e.g., interstitial lung disease) with or without preexisting hypoxia may have significant hypoxia during the procedure. Patients with lung cancer undergoing bronchoscopy may have other comorbid conditions (e.g., central airway obstruction, superior vena cava obstruction, metastatic lesions [bone, brain, liver] and electrolyte imbalance [hyponatremia and hypercalcemia]). Patients with pulmonary hypertension, elevated blood urea nitrogen (>30 mg/dL), chronic renal disease, and aspirin ingestion have an increased risk of postoperative bleeding. Interestingly, patients with recent myocardial infarction, unstable angina, or refractory arrhythmias often undergo bronchoscopy without significant complications.

A preoperative chest radiograph is mandatory; other investigations (e.g., complete blood count, electrolyte panel, and coagulation studies) are performed as indicated. Resting pulse oximetry prior to the procedure is essential in providing baseline information. Pulmonary function testing establishes the presence and severity of restrictive versus obstructive disease and the degree of reversibility, if any, with treatment. If respiratory failure is suspected or if the patient is on domiciliary oxygen, a preoperative arterial blood gas analysis is indicated.

Aims of anesthesia for bronchoscopy

During bronchoscopy, it is important to suppress the patient’s cough reflex and the hemodynamic response associated with bronchoscopy. Anesthesia may vary from no sedation, to mild to deep sedation, to general anesthesia. The type of anesthesia depends on the type of bronchoscope used—(FOB or rigid). The use of a topical anesthetic agent with or without sedation is used in most flexible FOB procedures. General anesthesia is usually required for rigid bronchoscopy and often in patients undergoing relief of a central obstruction with a FOB: however, sedation and local anesthesia may also be successfully used in both of these scenarios.

Preoperative preparation

After anesthesia and risks are discussed with a fasting (>6 h) patient, an antisialagogue (either atropine, 0.4-0.8 mg, or glycopyrrolate, 0.1-0.2 mg) is administered intramuscularly or intravenously 40 min prior to the procedure. Aerosolized bronchodilators, β₂-adrenergic receptor agonists, and anticholinergic agents are administered to patients with reactive airway disease before they undergo bronchoscopy. Corticosteroids are indicated during an exacerbation of reactive airway disease. The American Heart Association recommends subacute bacterial endocarditis prophylaxis for rigid bronchoscopy but not for bronchoscopy using a FOB unless the patient has a prosthetic heart valve, a surgically corrected intracardiac defect, or a history of endocarditis. Depending on the situation, patients on intravenous heparin should have the heparin discontinued 4 to 6 h before the procedure, and platelets should be transfused to maintain platelet levels greater than 50,000/mL. For patients undergoing any type of anesthesia, the American Society of Anesthesiology guidelines for monitoring should be followed.

Sedation

Without sedation, bronchoscopy is associated with increased cough, increased sense of asphyxiation, less amnesia for the procedure, and a significant increase in heart rate and blood pressure. Conscious sedation is usually achieved with intravenously administered incremental doses of midazolam (0.5-1.0 mg) or diazepam (1-2 mg). Intravenously administered opioids act synergistically with benzodiazepines to provide sedation and suppress airway reflexes but at the expense of potentiating respiratory depression. Fentanyl, sufentanil, alfentanil, and remifentanil are suitable opioid choices. Propofol can be used as a sedative agent, titrated in 10-mg doses, to provide conscious sedation and suppression of cough reflexes; however, significant hypotension and even apnea may result from excess drug administration. Intravenously administered dexmedetomidine has also been used to provide sedation for flexible bronchoscopy with a FOB.

Topical anesthesia for bronchoscopy

The sensory innervation of the upper airway is described in Table 156-1