Endobronchial electrocautery

INTRODUCTION — Electrocautery was first used in the 1930s to treat rectal cancer [1]. Endoscopic electrocautery subsequently has found wide use in the treatment of gastrointestinal lesions, such as colonic polyps, bleeding vessels, and biliary stenosis. Initial reports of the potential utility of electrocautery in the treatment of tracheal and bronchial tumors also appeared in the 1930s [2-4], but complications such as burns, tracheal perforation, and fatal hemoptysis dampened enthusiasm for the technique [5]. Refinements of the electrodes and other hardware and the use of sophisticated generators of high frequency current have improved the efficacy and safety of bronchoscopic electrocautery.

The technique of endobronchial electrocautery, also referred to as electrofulguration, diathermy, electrocoagulation, thermocoagulation, or electrosurgery, will be reviewed here. Other therapeutic bronchoscopy techniques are discussed separately. (See "Clinical presentation, diagnostic evaluation, and management of malignant central airway obstruction in adults" and "Bronchoscopic cryotechniques in adults" and "Endobronchial brachytherapy" and "Airway stents" and "Flexible bronchoscopy balloon dilation for nonmalignant airway strictures (bronchoplasty)".)

BASIC PRINCIPLES OF ELECTROCAUTERY — Three effects may be observed when electric current flows through human tissue:

●An electrolytic effect, in which chemical bonding is altered by the application of electrical energy

●A capacitance effect, in which the electrical potential difference of local structures is altered and which may stimulate nerves and muscles

●A thermal effect, due to the resistance of a tissue to the flow of electrical current

The rise in temperature of a given tissue during electrocautery is proportional to the square of the applied electrical current times the intrinsic resistance of the tissue; the latter is largely a function of vascularity and water content, with bone and fat having a higher resistance than skin and muscle [6]. Resistance and thermal effects are also increased by reducing the area of contact between the electrical probe and the patient, since the same quantity of current must then flow through less conducting tissue.

The temperature rises at different rates in different areas within a given tissue due to inhomogeneity of tissue density and the irregular distribution of electrical current. As a rule, the density of the electric current is largest, and the rise in temperature greatest, in the contact area between the coagulation electrode and tissue, and decreases with greater distance from this point.

Thermal destruction of tissue can be used for coagulation or resection:

Coagulation — Thermal coagulation (or "white coagulation") is caused by the relatively slow heating of tissue to approximately 70ºC (table 1). Above this temperature, the glucose-containing coagulum dehydrates and carbonizes. Three different coagulation modes are differentiated: soft coagulation, forced coagulation, and spray coagulation.

Soft coagulation — Soft coagulation is produced when no electric arcs pass between the coagulation electrode and the tissue; this prevents the tissue from becoming carbonized. The unipolar or bipolar electrode is brought into direct contact with the tissue to be coagulated, and less than 200 volts is employed. This mode is used when coagulation is needed solely to stop bleeding.

Forced coagulation — Forced coagulation results when electric arcs are generated between the coagulation electrode and the tissue in order to obtain deeper coagulation than is achieved with soft coagulation. The electrode is kept in contact with the tissue, a minimum of 500 volts is used, and cutting effects are avoided. This mode is used for vaporization of tissue.

Spray coagulation — Spray coagulation is characterized by the intentional generation of long electric arcs between a spray electrode and tissue without any direct contact between electrode and tissue. High voltages are necessary and tissue destruction and carbonization are readily accomplished. This mode is used when a large area is to be cut and vaporized.

Resection — Tissue can only be cut when the voltage between the electrode and the tissue is sufficiently high to produce an electric arc, effectively concentrating the electric current onto specific points of the tissue. The temperature produced at the points at which electric arcs contact the tissue is so high that the tissue is immediately evaporated or burned away.

Electric arcs cannot be triggered and tissue cannot be cut if less than 200 volts are used. Higher voltages are sometimes required, depending on the resistance characteristics of the tissue to be resected.

Tissue effects of electrocautery — There are three major effects of electrocautery:

●Vaporization – Cutting tissues is probably the result of boiling intracellular water and subsequent cellular explosion that disrupts the cells. The cutting action is therefore actually a vaporization effect.

●Coagulation – Coagulation is the result of a high or low electrical current that causes denaturization of proteins with occasional creation of a white hyalinized coagulum.

●Fulguration – Fulguration is the result of high current density at the electrocautery-tissue contact area, causing very high heat propagation and carbonization.

Regardless of these tissue effects, the degree of tissue damage is a consequence of the amount and duration of energy application. In addition, because of increases in resistance of damaged tissues as energy duration increases, the rate of tissue damage may actually decrease after prolonged applications, because the resistance of the tissue becomes greater than the ability of the current to penetrate it (figure 1) [7].

INDICATIONS AND EFFICACY — Electrocautery is a bronchoscopic technique that is used to treat nonmalignant or malignant airway lesions that are intraluminal and involve the central airways [8-13]. Treatment may be curative or palliative.

Malignant tumors — Endobronchial electrocautery is most commonly indicated for the treatment of symptomatic airway obstruction caused by bronchogenic carcinoma in patients who are not operative candidates (picture 1) [14-17]. In such patients, airway patency is restored in more than 80 percent of patients and symptoms are relieved in more than 70 percent [18]. Endobronchial electrocautery has been used to treat other causes of malignant airway obstruction as well, including endobronchial metastases.

The impact of endobronchial electrocautery on malignant airway obstruction has been illustrated by case series. In one series of 17 patients with locally advanced tracheobronchial malignancies who underwent endobronchial electrocautery, 15 patients had immediate reopening of the airway (89 percent) [14]. Eleven of those patients had restoration of >75 percent of the normal airway diameter, although only four patients had objective improvement in their physiological parameters. There were no deaths resulting from treatment, but minor bleeding occurred in one patient and aspiration pneumonia developed in another. Three patients required additional therapy.

Indolent malignant tumors are less common, but may also be treated effectively with endobronchial electrocautery [11,13]. This was illustrated by a series of 11 patients with intraluminal bronchial carcinoid tumors [11]. Electrocautery eradicated lesions in eight of the patients (73 percent). The remaining three patients could not be completely treated because the lesions were in the upper lobe bronchi.

Intraluminal microinvasive lung cancer that is radiographically occult has also been treated using endobronchial electrocautery. Treatment is most likely to be successful in patients who have strict intraluminal disease, visible distal margins (detected using autofluorescence), no invasion of the bronchial wall (identified by bronchoscopy), and no extraluminal growth (determined by high resolution computed tomography) [19,20].

Nonmalignant lesions — Endobronchial electrocautery can be used to treat nonmalignant obstructing lesions of the central airways (eg, granulation tissue, hamartomas, papillomas, lipomas). This was best demonstrated by a series of 38 patients who underwent endobronchial electrocautery [21]. Twenty-five patients had nonmalignant lesions, while 13 patients had malignant tumors. A total of 47 procedures were performed, of which 42 were deemed successful (89 percent).

Another setting in which endobronchial electrocautery is used to treat nonmalignant disease is when there is granulation tissue obstructing metal or hybrid stents. Electrocautery can be performed safely as long as certain precautions are adhered to, including avoiding supplemental oxygenation, avoiding direct applications of energy onto stent covering, and keeping energy applications to a minimum. These precautions are necessary because electrocautery can ignite the lining of covered metal stents, as well as break metal stents [22,23].

Other — Endobronchial lesions may cause hemoptysis or postobstructive pneumonia, both of which can be successfully treated with endobronchial electrocautery:

●Effective treatment of hemoptysis requires an accessible, visible lesion. In such circumstances, we are able to gain immediate hemostatic control in approximately 75 percent of patients. Adequate visualization of the tumor is essential in this situation and rigid bronchoscopy may allow more effective suctioning of briskly bleeding structures. (See "Rigid bronchoscopy: Intubation techniques" and "Evaluation and management of life-threatening hemoptysis".)

●Treatment (and prevention) of postobstructive pneumonia requires the restoration of at least partial airway patency. This can be achieved using endobronchial electrocautery.

CONTRAINDICATIONS — Contraindications include the following:

●Extrinsic compression of the airway is a contraindication to electrocautery. In this circumstance, there is no endobronchial tumor to remove, and electrocautery can produce a hole in the bronchus.

●As with all 'hot' thermal modalities, the use of electrocautery is contraindicated when the fraction of inspired oxygen (FiO₂) is >0.4.

●Unipolar electrocoagulation to remove tumor ingrowth from metal stents must be applied with extreme caution in order to avoid any contact of the electrode with the steel filaments, because melting and fracture of the stent can occur [24].

●Electrocautery with unipolar electrodes can deprogram cardiac pacemakers or implanted defibrillators and should be undertaken with caution in such patients [25].

EQUIPMENT — Bronchoscopic electrocautery requires electrocautery electrodes, a bronchoscope, and a generator of high-frequency current.

Electrocautery electrodes — Unipolar electrodes are most commonly used, but bipolar electrodes are also available [26]. Electrodes may be rigid or flexible. The rigid blunt electrode is 70 cm long and 2.5 mm in diameter, while flexible devices are 190 cm long and 2 mm in diameter. Electrodes are available in several configurations: blunt probe, knife, forceps, or wire snare. Rigid probes are more effective for debulking large tumors, while flexible probes permit treatment of smaller tumors, particularly in the upper lobes. In one large review, the blunt probe was used in 78 percent of cases, the knife in 15 percent, and the snare in 7 percent [26].

Electric current flows through the desired instrument, tissues, and a grounded neutral plate electrode attached to the patient. The neutral electrode must have a sufficiently large contact surface with the patient to prevent a cutaneous burn at its point of attachment.

Endoscope — Rigid electrocautery probes are used with a rigid bronchoscope, while flexible electrodes can be used through the working channel of a flexible bronchoscope. In one retrospective review, rigid bronchoscopy was performed in 62 percent of cases, whereas the rest were performed with flexible bronchoscopy [26]. However, in clinical practice and our experience, flexible bronchoscopic electrocautery is probably performed more frequently than reported in the literature, particularly by bronchoscopists who may or may not have access to rigid equipment, but who do have access to electrocautery equipment in their operating theaters, bronchoscopy suites, or endoscopy rooms. That being said, experts in advanced airway intervention often perform complex airway procedures with both the rigid and flexible bronchoscopes.

The ability of an electrode to deliver electricity depends in part on its diameter; for this reason, a flexible bronchoscope should be selected with as large an operative lumen as possible. The operative lumen of a rigid bronchoscope must have a diameter large enough for both the electrode and the rigid optic system. The larger channel bronchoscopes also provide greater ability for suctioning smoke and debris, as well as controlling any bleeding, should it occur from the resection/cauterization site.

For many years, the bronchoscope most widely used for endobronchial electrocautery was the Olympus 6 mm bronchoscope with a 2.6 mm working channel [6,14,27-29]. Since then, improvements have led to the development of many videobronchoscopes, including the newest models, which have large working channels and an insulated and electrically-grounded inner sheath. Working channels should allow the introduction of electrocautery probes, snares, and be sufficiently large to allow smoke evacuation during suction. If the bronchoscope is not grounded, there is a risk of the endoscopist receiving a shock if there is not a suitable low resistance pathway for current to pass through the patient to the neutral electrode. In addition, burns of the tracheobronchial tree may result if the bronchoscope makes contact with the patient near the point of electrocautery (figure 2). Bronchoscopists should obtain information regarding safety and applicability of electrocautery from manufacturers.

High frequency current generator — Most presently available generators are not configured in a manner that permits precise control of the power delivered to a lesion. Standard generators usually have power output settings that are graduated from 1 to 10; estimates about the actual power delivered at a given setting are often inaccurate, and the delivered voltage is variable. In addition, the resistance characteristics of a given tissue change as it is cauterized, and charring can foul the electrode. This promotes adhesion to the tissues, and the charring serves as an insulator that prevents coagulation from progressing.

High frequency generators are regulated with a microprocessor and a voltage stabilizer, which allow precise control of the thermal coagulation process. Typically, these generators switch off automatically at 100ºC in order to prevent the production of exploding steam pockets that can cause tissue perforation, rupture, and hemorrhage (the "popcorn effect"). Additional safety features, such as isolated outputs and precise control of delivered power (in watts), are also included.

TECHNIQUE

General precautions — General precautions are required to prevent electrical injuries to the patient, clinician, and support staff. The patient should not have any contact with metal from the table, and sheets should be dry. The neutral plate electrode must be placed in its entirety on the patient. If the contact surface is not sufficient, the current will pass from the patient through smaller contact points which, by virtue of their lesser area and consequently higher resistance, may cause burns.

Monitoring — At a minimum, cardiac rhythm and oxygen saturation should be continuously monitored and blood pressure frequently assessed during the procedure. Routine intraoperative monitoring protocols are generally used if the electrocautery is performed under general anesthesia. The procedure usually lasts between 20 and 60 minutes if performed through a rigid bronchoscope, and longer if a flexible scope is used.

Anesthesia — General anesthesia is usually required if endobronchial electrocautery is performed through a rigid bronchoscope, although dissociative anesthesia with sedatives and neuroleptics is occasionally employed. Local anesthesia and moderate sedation can be used when the procedure is performed through a flexible bronchoscope with flexible electrodes. Readministration of sedatives may be required during the procedure because a longer duration of sedation is needed than for a routine bronchoscopy.

Flammable anesthetic agents should not be used during the procedure because of the risk of ignition. In addition, the fraction of inspired oxygen should be kept at the lowest level required to maintain adequate patient oxygenation in order to reduce the risk of tracheal fires. The maximal fractional concentration of inspired oxygen for use with electrocautery (or bronchoscopic laser resection) is 0.4.

Procedure — The flexible endoscope can be introduced by either the nasal or oral route or via an endotracheal tube. The procedure is carried out under direct vision, with the electrode introduced within the tube of the rigid bronchoscope beside the optical telescope, or in the operating channel of the flexible bronchoscope.

The operator assesses the lesions to be treated, noting their position and the extent of stenosis or extrinsic compression, whether they are projecting or infiltrating, and whether they are hemorrhagic or bland. The electrode must protrude from the end of the bronchoscope by about 2 cm and is then placed in contact with the lesions to be destroyed. The high frequency generator is adjusted to automatic control of soft coagulation, with a power setting generally between 40 and 60 watts, or is adjusted to the visible coagulative effect if a first-generation machine is used. Other modalities, such as forced or spray coagulation or cutting mode, are used as required, and different electrodes (eg, blunt electrode, wire snare, forceps, or knife) are selected as needed. It is useful to clean the tip of the electrode frequently, because buildup may damage the electrode and/or reduce the delivered power.

Two main methods of electrocautery are used: debulking of tissue by means of a cutting loop, or direct electrodestruction of tissue. Both techniques are effective and provide good results, but smoke needs to be suctioned during resection, and an unpleasant burnt tissue smell is given off. Treatment is continued until sufficient patency of the airway lumen is restored and/or bleeding arrested.

●Resection of tissue generally is accomplished by the use of a unipolar wire snare apparatus similar to that used to excise colonic polyps. The technique is most suitable for narrow-based lesions causing incomplete bronchial obstruction, such that the instrument can be passed distal to the tumor and the base snared.

The device is passed through the endotracheal tube alongside a flexible bronchoscope, or inside the operating channel of the flexible or rigid bronchoscope, looped around the base of the tissue to be resected, and then energized [10,15,30,31]. Debrided tissue fragments are often too large to be removed through the bronchoscope and must be extracted with forceps.

●Tissue can be directly destroyed with electrocautery to achieve an effect similar to that seen with neodymium yttrium aluminum garnet (Nd:YAG) laser vaporization [30,31] (see "Bronchoscopic laser in the management of airway disease in adults"). A blunt cautery probe is directly applied to burn, desiccate, and vaporize obstructing tissue. Unipolar probes have generally been used for this purpose, but a bipolar flexible electrocautery probe (BICAP) has been adapted for use through the operating channel of a fiberoptic bronchoscope [32-34]. BICAP has seen widespread use for the ablation of gastrointestinal lesions and offers the advantage of not requiring a grounding plate, because the current completes its arc through the two tips of the probe. Any residual tissue that adheres to the tip of the electrode should be wiped off when the probe is removed.

Complications — Endobronchial electrocautery is usually well tolerated. A number of complications have been described [14,16,25,26,30,31,33,35-38]:

●Application of deep electrocautery too close to the bronchial wall may result in airway perforation and pneumothorax or pneumomediastinum. Cartilaginous rings may be destroyed, leading to a loss of structural support, chondritis, tracheo- or bronchomalacia, and/or secondary stenoses.

●Electrocautery generates electric arcs and can cause tracheal fires or ignition of endotracheal tubes, fiberoptic bronchoscopes, or silicon endoprostheses. The risk of fire is increased if high fractions of inspired oxygen are used. The maximal fractional concentration of inspired oxygen for use with electrocautery (or bronchoscopic laser resection) is 0.4.

●Bleeding can result from penetration of the probe into the tumor, but generally stops quickly due to thermocoagulation. Significant bleeding occurs in approximately 2 percent of cases, and may be more common with vascular neoplasms such as carcinoid tumors and hamartomas.

●Aspiration pneumonia has been reported, either as a complication of anesthesia or due to aspiration of postobstructive pus into the contralateral lung immediately after debulking.

●Electrical shock and/or electrical burns to the patient or operator may occur if unipolar leads and a nongrounded apparatus are used (figure 2).

●Ventricular fibrillation has occurred when electrocautery is used near the heart, and interference with the function of implanted cardiac pacemakers or defibrillators may occur.

Generally speaking, the complications of endobronchial electrocautery are similar to those encountered using argon plasma coagulation or bronchoscopic laser ablation [39], which are described elsewhere. (See "Bronchoscopic laser in the management of airway disease in adults" and "Bronchoscopic argon plasma coagulation in the management of airway disease in adults".)

Postoperative care — Electrocautery does not require any particular immediate follow-up care in the absence of complications. Postprocedural chest imaging studies are usually not necessary, but may be warranted on a case by case basis to document resolution of atelectasis or other abnormalities, or in case of complications to help ascertain lung parenchymal damage in case of an airway fire. After bronchoscopic electrocautery, most patients can return home the same day.

SUMMARY AND RECOMMENDATIONS

●Indications – Electrocautery is a bronchoscopic technique that is used to treat nonmalignant or malignant airway lesions that are intraluminal and involve the central airways. Treatment may be curative or palliative. (See 'Indications and efficacy' above.)

●Contraindications – Extrinsic compression of the airway is a contraindication to electrocautery. In this circumstance, there is no endobronchial tumor to remove and electrocautery can produce a hole in the bronchus. (See 'Contraindications' above.)

●Equipment and procedure – Endobronchial electrocautery can be performed under local anesthesia and moderate sedation using a flexible bronchoscope or under general anesthesia with a rigid bronchoscope. (See 'Anesthesia' above and 'Procedure' above.)

●Complications and postoperative care – Endobronchial electrocautery is usually well tolerated and results in minimal morbidity, although complications have been reported. It does not require immediate follow-up care in the absence of complications, and patients usually can return home the same day. (See 'Complications' above and 'Postoperative care' above.)