Advances and safe use of energy devices in lung cancer surgery

The standard treatment for clinical stage I–II non-small cell lung cancer is surgery. Based on the results of a clinical trial conducted in 1995, lobectomy and lymph node dissection of the hilar and mediastinum are the standard surgical procedures for non-small cell lung cancer [1]. Various minimally invasive approaches have been developed over the last decade, ranging from conventional thoracotomy to video-assisted thoracoscopic surgery (VATS), robot-assisted thoracoscopic surgery, uniportal VATS, and subxiphoid approach [2‐4].

In surgical treatment for lung cancer, energy devices and automatic suture devices have significantly contributed to the evolution and safety of surgical treatment regardless of procedures or approaches. As for energy devices, monopolar devices, advanced bipolar devices, and ultrasonic energy devices are frequently used. The improved vascular sealing function of advanced bipolar devices and ultrasonic energy devices is remarkable. Ligation, a classical hemostasis method, is no longer necessary for a small vessel. While they improve the quality and safety of surgery, their misuse can put the patients at risk. Therefore, it is desirable to use them only after understanding their principles and basic mechanisms.

This review covers different energy devices, electrosurgery-related injuries, energy device education, and operating room fire risks with the aim of providing an overview of advances in and the safe use of energy devices. In particular, we focused on the effects, adverse events, and better choice of energy devices in lung cancer surgery.

To identify the effects and adverse events of energy devices, a literature search within the PubMed, Medline, Scopus and Web of Sciences databases were searched electronically from their inception up to 16 April 2021 (Supplement file). Papers published until the date of the review that contained these terms in the abstract were selected.

Reference lists of the identified papers and relevant manuscripts were examined. The titles and abstracts’ information were selected for subject importance. Studies that were not definitively excluded on the basis of abstract information were also selected for full-text screening. The full text of all relevant researches to evaluate the possibility of inclusion was examined. The criteria of exclusion were as follows: (1) studies not focused on the topic selected, (2) papers in a language other than English and Japanese, (3) duplicates, and (4) studies not available from libraries for full-text assessment. The results and key information obtained were summarized by means of a narrative approach.

The publications indexed as articles, proceedings papers or reviews were reviewed, including the references of the publications to identify additional relevant articles; finally, a total of 77 papers were included in the review. The papers were decided to categorize these articles based on theoretical considerations.

Surgical medicine has evolved using hemostatic methods. Electrosurgical devices have been in use for approximately 100 years [5] (Ref; 1. Evolutions and revolutions in surgical energy). Over recent years, while advanced equipment has been developed and clinically introduced almost every year, such equipment has been utilized without systematic education, and a lack of knowledge about energy devices has been revealed, irrespective of experience [6].

Energy devices cause various adverse events, ranging from burns and organ damage to operating room fires; nonetheless, these events are not well known. Electrosurgery-related injuries are estimated to occur at an incidence of approximately 40,000/year [7] or approximately 1–2 per 1000 operations during laparoscopy [8]. The impact is significant, with paid claims of nearly 600 million USD for electrosurgical injuries in 1999 [7]. Moreover, 18% of surgeons have reportedly experienced electrosurgery-related injuries, and 54% have known a colleague who experienced such an injury [9].

The requirement for systematic education has increased against the backdrop of electrosurgery-related injuries in North America. Led by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), surgeons, operating room nurses, anesthesiologists, electrical engineering specialists, educational specialists, and statistics experts have organized a team to develop FUSE, a specialized education program for the safe use of energy devices [5] (Ref; Introduction). The contents of FUSE are wide-ranging, focusing on the principles and safe use of monopolar devices, bipolar devices, ultrasonic energy devices, radiofrequency devices, microwave ablation, cryoablation, and endoscopic energy devices. Textbooks and e-learning are the modes of learning, and FUSE is also used as a qualification test and can be certified.

In Japan, the Pharmaceuticals and Medical Devices Agency (PMDA) has a mechanism to call attention to adverse events that can occur with medical devices and drugs that are disseminated worldwide [10]. Nevertheless, electrosurgery-related injuries still occur. Systematic education is necessary for their elimination. Therefore, lectures regarding the safe use of energy devices have been given to medical staff and students by incorporating material regarding these devices into the syllabus [11, 12].

Electrosurgery uses radiofrequency (RF) alternating current (AC) to increase the intracellular temperature. In an AC, the polarity of intracellular ions and/or electrons rapidly and regularly fluctuates, and this mechanical energy changes to thermal energy, increasing the intracellular temperature near the tip of the RF energy device. If the cellular or tissue temperature is maintained at 50 °C for 6 min, cell death occurs. If the temperature reaches 60–100 °C, cell death instantaneously occurs along with cellular desiccation and protein coagulation. When the temperature reaches 100 °C, cells are vaporized through liquid–gas conversion to steam [5] (Ref; 2. Fundamentals of Electrosurgery Part I).

Intracellular thermal changes using AC are affected according to Ohm’s law [13]. Electrosurgery generators (or electrosurgical units; ESUs) convert low-frequency AC into higher frequency outputs and adjust current (I), voltage (V), and current time (duty cycle) to achieve various modes such as “coagulation” and “cut.” The impact of RF energy on tissues is related to the waveform of the ESU output [12, 14].

The mode depends on the current time and peak voltage. According to power (W) = voltage (V) × current (I), even with the same output, if the current time is long (continuous wave), the voltage tends to be low, and if the current time is short (interrupted wave), the voltage tends to be high. Low-voltage continuous outputs correspond to “cut” and “soft coag” modes. This results in a predictable zone of coagulation with higher quality and consistency. Therefore, low-voltage continuous outputs are generally the most effective for sealing blood vessels. The outputs of advanced bipolar devices are predetermined by low-voltage continuous outputs. However, the “soft coag” mode does not have a cutting effect, even under a focusing current density. In contrast, high-voltage interrupted outputs correspond to “fulgurate,” “coag,” and “spray” modes. In general, “spray” has the lowest duty cycle and highest peak voltage. These modes create a superficial and inhomogeneous zone of desiccation and coagulation that is unsuitable for vessel sealing.

Monopolar systems include two separate instruments in the circuit: an active electrode and a dispersive electrode. Monopolar systems include the entire patient in the circuit. In other words, it is not possible to know exactly where the current flow in the body. This recognition is essential for understanding the mechanisms of electrosurgery-related injuries. The thermal effect is proportional to the current density squared [5] (Ref; 2. Fundamentals of Electrosurgery Part I). Adverse events can occur when the current density increases outside the tip [15].

Bipolar devices are designed with both electrodes positioned on the same surgical device [5] (Ref; 5. Bipolar Electrosurgical Devices). When compared with monopolar devices, bipolar devices can control the flow of current through only the targeted tissue area and reduce the risk of remote electrosurgery-related injuries. However, the clinical effects of conventional bipolar devices are left to visual judgment. The degree of compressed tissue also depends on the tactile sensation of the surgeon. Therefore, conventional bipolar devices have risks in terms of improper or over-compression or activation of the tissue which may result in collateral damage (Fig. 3) and ineffective sealing.

New bipolar devices have been developed to overcome these limitations. So-called “advanced bipolar devices” such as LigaSure™ or EnSeal™ incorporate sophisticated microprocessors and feedback systems that monitor impedance and temperature and automatically adjust the delivery of the current to ensure adequate tissue sealing while minimizing collateral damage. It is also called a “vessel sealing device” or “vessel sealer” because the accuracy of sealing has improved dramatically. Advanced bipolar devices provide audible signals that indicate when adequate coagulation has been achieved. When energized with staples, the impedance deviates from the normal tissues; thus, the mechanism is safer because it does not erroneously energize. Advanced bipolar devices are capable of constantly achieving hemostatic tissue seals in vessels up to 7 mm in diameter.

As the temperature is controlled below 90 °C, the effect around the sealing tissue is minimal; nevertheless, collateral damage is not eliminated. Although the temperature of LigaSure™ is lower than that of ultrasonic devices, the thermal spread of LigaSure™ is significantly greater than that induced by ultrasonic devices [19]. Moreover, using LigaSure™ around nerves may have a risk of paralysis if the distance to the nerve is less than 3 mm.

Advanced bipolar devices can be used regardless of the tip direction and cannot cut at the tip. Surgeons need not pay much attention to contact with vital structures after activation, although ultrasonic devices may drill into the tissue (Fig. 4). Due to the better sealing function, care must be taken not to seal unintended layers (Table 1).

Ultrasound refers to sound waves that are greater than 20 kHz. Ultrasound for diagnostic imaging wave frequencies ranges from 2 to 18 MHz. Ultrasonic energy devices such as the Harmonic™ or Sonicision™ contain piezoelectric ceramic discs that convert electrical energy into mechanical motion that is transferred to the shaft where it is amplified by silicon nodes [5] (Ref; 7. Ultrasonic Energy Systems). The active blade of the ultrasonic energy device vibrates at a rate of 23–55 kHz. This effect is caused by the mechanical interaction between the oscillating tip of the device and tissue. The amount of mechanical energy applied to the tissue is adjusted by varying the length of the excursion of the blade, which ranges between 50 and 100 µm. A larger amount of blade excursion results in more rapid cutting and less thermal spread, but also minimizes hemostasis. A shorter blade excursion results in less cutting and a greater degree of collateral thermal injury, which results in better hemostasis. Not only the excursion of the blade but also the lifting and tensioning of the tissue causes a difference in mechanical energy; therefore, this device would make a difference depending on the surgeon. Prolonged or inappropriate activation can cause contact tissue damage or blade fractures.

When handling ultrasound energy devices, surgeons should always focus on making contact with vital structures. Ultrasound energy devices have a concerned phenomenon, so-called “cavitation”, that it may damage a distant position different from the target tissue. However, no abnormal findings are found unless it is close to 0.1 mm [20]. The key feature is that it cuts at the tip (Fig. 4), and the cutting speed is faster than that of advanced bipolar devices [19]. There is no need to apply a dispersive electrode, and the absence of an electrical current passing through the patient’s body eliminates the complications of monopolar devices.

Advanced bipolar devices and ultrasonic energy devices have advantages, disadvantages, and commonalities (Table 2). Therefore, it is important to use them safely and understand their principles and characteristics.

Various reports on the sealing effect of advanced energy devices exist. The mean burst pressure of the small pulmonary arteries is 4.3-fold lower after sealing than after ligation and 6.4-fold less after ligation of thick pulmonary arteries with LigaSure™. Sealed pulmonary arteries > 5 mm in diameter had a burst pressure that was 50% less than that of smaller arteries. Histologic examination after sealing demonstrated only fusion of the adventitia, and the intima and media were replaced and invaginated into the vessel lumen [21]. The EnSeal™ device resulted in a pressure tolerance of > 75 mmHg in the acute phase [22]. The mean bursting pressure with Harmonic™ was equal to or greater than that of a vascular stapler in a simulated ex vivo model [23]. Advanced energy devices provide a seal that was superphysiologic in that all burst pressures were > 250 mm Hg [24]. The sealing effect of the ultrasound energy device is similar to that of advanced bipolar devices [23‐26]. The sealing time of the ultrasound energy device was significantly shorter than that of advanced bipolar devices [26].

A prospective study demonstrated that LigaSure™ sealing without reinforcement allowed secure treatment during lung resection of pulmonary arteries as large as 5 mm in diameter and pulmonary veins as large as 7 mm [27]. This study reported a postoperative hemorrhage that occurred in the case of a pulmonary artery as large as 7 mm without any additional reinforcement. Thus, pulmonary arteries > 5 mm are appropriate for central treatment such as clipping and ligation on the hilar side [28].

Overall, sealing using advanced energy devices is safer to use in vessels of 5 mm or less. As it is difficult to accurately measure the vessel diameter intraoperatively, it is challenging to use vessel diameter empirically based on visual information with reference to the diameter of the device. Any force in the sealing area may cause bleeding. In addition, arteries, veins, and lymphatic vessels have histological differences. Moreover, patients with diabetes, vasculitis, and arteriosclerosis have different tissues. If bleeding is a concern, ligation should be performed, or an automatic suture device should be used instead of an advanced bipolar device alone.

Pulmonary resection requires a skin incision, separation of the subcutaneous tissue, and access to the thoracic cavity. In addition, anatomical lung resection requires cutting of pulmonary veins, pulmonary arteries, bronchi, and interlobar or intersegment divisions. In the case of lung cancer, dissection of the hilar and mediastinal lymph nodes is also performed. Since energy devices are used in each of these processes, their selection criteria, merits, and precautions are described as follows (Table 3).

Operating room fires are a rare adverse event, estimated at 550–650 fires annually in the United States [73]. Ninety-five percent of cases are mild, but 5% are serious, with 20–30 cases annually leading to death. Seventy percent of ignition sources are electrosurgical equipment. Fires occur around the head, neck, face, or upper chest and in the airway [74, 75].

In lung cancer surgery, tracheoplasty, bronchoplasty, tracheostomy, and bronchoscopic procedures are associated with a risk of operating room fire. In tracheostomy, tracheoplasty, and bronchoplasty, a cold knife rather than an energy device should be used for incisions of the trachea and/or bronchus [36]. Oxygen in the airways can ignite. After the incision, an electrosurgical device should not be used because of the oxygen that is released into the surgical field. When oxygen is required, isolated lung ventilation or ventilating the area should be considered. To prevent operating room fires during oxygen administration, the lowest required concentration and flow rate of oxygen should be used, or intermittent rather than continuous administration should be considered.

Airway burns may also occur when using energy devices for cauterization and hemostasis of intra-airway tumors in bronchoscopic procedures. The main energy devices used for bronchoscopic procedures are lasers, argon plasma coagulation, polypectomy snare, and hot biopsy forceps. All these can cause ignition during treatment at high oxygen levels. If the oxygen concentration is 30% or more, there is a risk of ignition [76, 77], which is an important consideration in respiratory management. For airway bleeding, energy devices should not be used, and adrenaline-diluted saline and thrombin should be prioritized.

There is a time-tested adage as follows: “You cannot cut, what you cannot see.” A good surgery requires a simple maneuver that simultaneously promotes both adequate surgical site exposure and sufficient traction. This can be achieved by two principles: “off the ground” and “counter traction.” “Off the ground” involves a procedure that separates the targeted tissue from the deep tissue and protects the deep tissue. “Counter traction” involves a procedure wherein appropriate tension to the targeted tissue is applied in the opposite direction by the surgeon and assistant, thus facilitating appropriate incision of the target tissue. For the safe use of energy devices, both “off the ground” and “counter traction” need to be considered (Fig. 6). In particular, both principles should be consciously applied when using a spatula-type monopolar device. Depending on the surgical approach, different energy devices are useful. In thoracotomy and multiple-port VATS, “counter traction” and “off the ground” are possible at will, and a spatula-type monopolar device is appropriate. However, in uniportal VATS, an assistant cannot freely assist; therefore, the use of a spatula-type monopolar device is restricted [78]. Instead, the hook type is more convenient in uniportal VATS, because it allows the operator to implement the “off the ground” principle himself or herself. However, even with different surgical approaches, advanced bipolar devices and ultrasonic energy devices work on the sandwiched tissue, reducing awareness of “counter traction.”

The present review examined energy devices, including monopolar devices, bipolar devices, and ultrasonic devices; electrosurgery-related injuries; fundamentals of electrosurgery; operating room fire risks; and basic principles of surgery. Understanding these energy devices can lead to more effective and safer use and can facilitate better decision-making regarding these energy devices in lung cancer surgery.