Anesthetic Considerations for Bronchoscopic Procedures

Function

Over 500,000 bronchoscopies are performed annually in the United States.[2] A thorough pre-procedure assessment should be done that includes the patient's past medical and surgical history, medications, airway exam, and time since last oral intake. Additionally, pulmonary function tests and arterial blood gas can offer valuable information about the patient’s respiratory and metabolic status. Special attention should be given to the patient’s pulmonary function as instrumentation from the bronchoscopy may induce complications, including bronchospasm, laryngospasm, and airway obstruction. As with any invasive procedure, the standard American Society of Anesthesiologists monitors should always be used (pulse oximeter, electrocardiography (ECG), blood pressure device, and a temperature monitor).[2]

Anesthesia for flexible bronchoscopy depends on the procedure type and patient factors. Patients presenting for bronchoscopy might have limited cardiac and pulmonary function. Patients might become apneic even with minimal sedation. An anesthesia provider should be prepared to intervene if rapid oxygen desaturations and airway obstructions occur. Airway interventions include nasopharyngeal trumpet, bag-mask ventilation, and oral intubation with an endotracheal tube (ETT).[1] 

There are many considerations that an anesthesia provider needs to be aware of during a bronchoscopy. A thorough preoperative assessment must be done. The anesthetic plan is based on the technique of anesthesia used in conjunction with patient comorbidities. Both the bronchoscopy operator and anesthesia team must agree on the anesthetic plan. A variety of types of anesthesia can be used, and some in combination. Discussed below are some anesthesia types that can facilitate a bronchoscopy. 

Topical Anesthesia

One technique is topical anesthesia, in which a local anesthetic, typically lidocaine, is used to produce topical anesthesia to the posterior oral cavity and base of the tongue.[2] Patients gargle 1% lidocaine with optional additional lidocaine applied via spraying into the oropharynx and laryngopharynx. The anesthesia provider must remain vigilant following this topicalization, as there is potential for aspiration due to relaxation of the pharyngeal and laryngeal muscles.[2] Topical anesthesia is often used in conjunction with Monitored Anesthesia Care (MAC) or Total Intravenous Anesthesia (TIVA).

Regional Anesthesia

Another anesthesia technique is regional anesthesia via a superior laryngeal nerve block. This nerve block will blunt the cough reflex, which is very sensitive to airway irritation. Precise positioning of the superior laryngeal nerve block is important due to the potential of injuring surrounding structures relative to the nerve. As the superior laryngeal nerve (internal branch) runs with the superior laryngeal artery just below the greater cornu of the hyoid, the block needle should be positioned perpendicular to the skin aiming just below the greater cornu of the hyoid bone for in-plane ultrasound-guided technique. Potential complications include tracheal injection, arterial/nerve injection, thyroid injection, and hematoma.[3] Interventions to be taken if complications arise include securing the patient's airway and consulting an otolaryngologist physician.  When performing regional anesthesia, there is always a risk of local anesthetic systemic toxicity (LAST), so a 20% lipid emulsion should be immediately available for rescue in the event of vascular injection of local anesthetic.

Monitored Anesthesia Care (MAC)

Nearly all anesthesia for bronchoscopy involves the anesthesia team providing light or moderate sedation.[4] MAC is the most commonly utilized anesthesia type for bronchoscopy. Commonly used medications for MAC are midazolam, fentanyl, propofol, remifentanil, dexmedetomidine, and ketamine.[5] Knowledge of the indications and side effects of each medication is paramount. Often multiple medications are used in combination. The most common combination is propofol and midazolam.[5] Special consideration for elderly patients needs to be taken as they are more prone to becoming apneic than the younger general population. The most commonly used sedative medication is propofol due to the rapid onset, antiemetic, anticonvulsant, antipruritic, and bronchodilator properties. It is also suitable for patients with renal and hepatic insufficiency. Common side effects of propofol are hypotension, respiratory depression, and pain during injection.[6] Propofol is commonly used in TIVA techniques. In contrast to inhalation anesthesia via sevoflurane or isoflurane, TIVA techniques offer advantages in that anesthetic agents can be administered independently of ventilation.[7]

Total Intravenous Anesthesia (TIVA)

This type of anesthesia is a form of general anesthesia in which medications are administered solely intravenously. No inhalation agents are used. TIVA is useful in rigid bronchoscopy as ventilation is often interrupted. This is the only technique used in Jet Ventilation (JV). Commonly using JV, a neuromuscular blocking agent is used for complete muscle paralysis in conjunction with a sedative-hypnotic.[7] TIVA is indicated for patients with absolute contraindications to inhalation agents, such as those with a history of malignant hyperthermia.[8] Some disadvantages to TIVA include the inability to measure blood concentrations of anesthesia, dose-dependent suppression of airway reflexes, and errors in infusion pump devices. An additional disadvantage is unrecognizable IV infiltration and extravasation of medication into the surrounding tissue. This can result in compartment syndrome, which manifests as pain out of portion to the injury, pallor, pulselessness, paresthesia, and paralysis of the affected area.[9] Compartment syndrome is an emergency and should be treated quickly with surgical intervention via fasciotomy at the affected site.

General Anesthesia

Patients requiring deeper sedation with general anesthesia must have their airway secured via an ETT or laryngeal mask airway (LMA).  A bronchoscope can be inserted through these airway devices using specialized adaptors. Sharing an airway has potential complications, including airway obstruction, mechanical trauma, inadequate ventilation, barotrauma, inadequate anesthetic level with possible awareness, laryngospasm, and bronchospasm.[10] General anesthesia also presents the risk of increased hemodynamic instability, as well as malignant hyperthermia in susceptible individuals.  Hemodynamic instability may require the use of vasoactive medications.  A family history of malignant hyperthermia, including unexplained death during or shortly after a general anesthetic, should prompt the anesthesia provider to switch to a safer anesthetic choice such as TIVA and avoid volatile agents as well as succinylcholine.  Complications and necessary interventions must be communicated with the bronchoscopy operator.

Jet ventilation during bronchoscopy requires oxygen delivery at high pressure, which has unique and potentially catastrophic sequelae.[10] JV has the potential to cause significant barotrauma. Rapid deterioration of oxygen saturation and carbon dioxide levels during JV procedures should alert the provider to the possibility of pneumothorax or pneumomediastinum.[10] If a tension pneumothorax is suspected, then rapid needle decompression in the second intercostal space of the midclavicular line (of involved hemithorax) must be performed to prevent cardiorespiratory collapse.

Issues of Concern

Potential complications of bronchoscopy include hypoxemia, airway obstruction, laryngospasm, cough, bleeding, airway fire, pneumothorax, tension pneumothorax, and air emboli.[4]  Complication occurrence varies between 0.4% and 1%. Patient comorbidities play a big role in the complication rate, as does the anesthesia provider and bronchoscopy technicians' expertise. Preparation with the necessary equipment in case of a potential complication is paramount. Ideally, bronchoscopy should occur in an operating room where the necessary equipment for airway management is readily available. 

Bronchoscopy patients require extensive suctioning as secretions build up in the oral airway. A common complication of bronchoscopy is aspiration pneumonia, in which gastric and/or oropharyngeal fluids enter the lungs. Rapid onset fever, cough, dyspnea, and crackles on lung auscultation are common clinical features.[11] Conditions that predispose to aspiration pneumonia are altered consciousness, dysphagia, neurologic disorders, pharyngeal anesthesia, increase in age, gastroesophageal reflux disease, gastroparesis, and poor dental hygiene. [11] Treatment for aspiration includes immediate suctioning and turning the patient's head to the side to prevent further aspiration.[12] Antibiotics are only warranted for those who meet bacterial pneumonia diagnosis, and oral amoxicillin-clavulanate is the antibiotic of choice.[12]

Oxygen delivery during bronchoscopy is a special consideration due to the instruments introduced during the procedure that necessitates a shared airway. Oxygen is typically delivered via a nasal cannula, but an LMA or ETT can be used. Foreign bodies present in the upper airway are often an indication for a bronchoscopy, and a pre-operative assessment should be done with additional emphasis on the timing, the precise location, and the shape of the foreign object. A preoperative chest radiograph, computed tomography scan, and/or magnetic resonance imaging are helpful, but often the urgency of the airway obstruction precludes imaging before intervention.[13] Invasive monitoring such as an arterial line for blood pressure management and central line catheter for rapid fluid administration and vasopressors may be needed in more complex cases.  These invasive monitors are used only for hemodynamically compromised patients. 

For routine bronchoscopy, careful attention must be paid to patient comorbidities.  Patients with pulmonary hypertension, morbid obesity, severe deconditioning, pulmonary fibrosis, severe valvular disorders, poorly controlled asthma, interstitial lung disease, certain autoimmune disorders, and severe chronic obstructive pulmonary disease (among many other disease states) tend to have poor oxygen reserves, and short periods of apnea are not well tolerated. Careful consideration in patient selection is important because patients with comorbidities that are not stable enough to tolerate brief periods of apnea should not undergo routine diagnostic bronchoscopy where alternative diagnostic or therapeutic interventions may exist.[14]

Clinical Significance

Flexible versus Rigid Bronchoscopy

The pros and cons of flexible and rigid bronchoscopy are presented below. Both the anesthesia team and bronchoscopic operator need to consider the risks and benefits of flexible versus rigid bronchoscopy. In addition, patient comorbidities and procedure goals need to be discussed in order to have the best outcomes. As with every procedure, patient consent needs to be obtained. 

Pros of Flexible Bronchoscope[1][4]

•       Can be performed at the bedside and under moderate sedation
•       The patient is spontaneously breathing
•       The bronchoscope can be easily maneuvered in the airway

Cons of Flexible Bronchoscope

•       Laryngeal edema
•       Bleeding
•       Pneumothorax

Pros of Rigid Bronchoscopy[4]

•       Can be inserted past airway obstruction

Cons of Rigid Bronchoscopy[1][4]

•       Must be performed in the operating room
•       Oral and pharyngeal damage
•       Limited visualization
•       Nonflexible metal rod

Enhancing Healthcare Team Outcomes

An interprofessional team for bronchoscopy includes bronchoscopy operators (pulmonologists, intensivists, otolaryngologists), anesthesiologists, nurse anesthetists, nurses, operating room technicians, and pharmacists. An interprofessional team approach that emphasizes good communication will offer the best patient outcomes. It is paramount that all healthcare providers know the patient’s medical history and potential complications of the bronchoscopy procedure. Complications can arise at any time during the procedure, and swift interventions need to be undertaken for optimal results. It takes a whole team and excellent communication to provide quality care.

During postoperative care, potential bronchoscopy complications need to be addressed, and proper communication is important. The provider in the recovery unit should be aware of any oxygen desaturation, level of consciousness alterations, chest pain, shortness of breath, voice changes, hoarseness, dysphagia, hematoma, and bleeding. Open communication is the key to ensure good outcomes. Rapid physical examination, laboratory, and imaging are imperative to stop the further progression of a complication. [Level 5]