stray current is dispersed over a larger surface area. The extent of coupling injuries depends on the magnitude of the current applied.
Figure 5.6 Direct coupling occurs when the active electrode is in close proximity to another metal instrument and activation of the electrosurgical device occurs, transmitting current to the metal instrument and ultimately the adjacent structures. ESU, electrosurgical unit.
Source: From Dubiel et al.[1].
Figure 5.7 Indirect coupling or insulation failure occurs when there is damage to the insulation of the active electrode. This allows for stray current to be discharged and may result in injury to neighboring tissues. ESU, electrosurgical unit.
Source: From Dubiel et al. [1].
Bipolar Electrosurgery
Bipolar electrosurgical devices differ from monopolar in that both the active and passive electrodes are contained within the same electrosurgical device, meaning that the current does not pass through the patient. This achieves the desired hemostatic effect using less energy (30–50 W), while minimizing the risk to the patient as the current passes from one electrode to the tissue and then to the other electrode. Bipolar forceps require more time to coagulate vessels and are more apt to stick to the vessel and carbonize tissues, which can lead to further hemorrhage upon removal. Bipolar forceps have minimal use in tissue dissection and are used for coagulation of tissue only and not cutting. Traditional bipolar electrosurgery devices use forceps with a foot pedal connected by a cord; thus, the current remains local. These traditional bipolar devices can coagulate vessels 3 mm or smaller in diameter [12]. Lateral thermal damage has been reported to occur up to 8 mm from the coagulation site [13, 14]. Bipolar instruments used in MIS can coagulate and cut if a cutting blade is present in the instrument. Bipolar endoscopic scissors are available; however, these scissors may cut the tissue before sufficient coagulation. Additionally, the cutting blade on some instruments can push the tissue out of the jaws, which leads to incomplete cutting, and eventually these blades become dull. Bipolar endoscopic instruments are more expensive than monopolar instruments.
Tissue Fusion Device
Tissue fusion technology, or vessel sealant devices, are bipolar electrosurgery devices that rely on tissue fusion for control of blood vessels and lymphatics. These devices measure tissue impedance and subsequently deliver the appropriate the amount of energy to achieve a safe seal. Vessel sealant devices have been approved for sealing vessels up to 7 mm in diameter [15–17].
This system uses low voltage with high current. The generator senses tissue impedance (electrical resistance) and adjusts the energy to achieve hemostasis while minimizing heat and tissue carbonization (Figure 5.8). An acoustic signal is delivered to indicate that the sealing cycle has been completed. This system denatures elastin and collagen, and the strength of the seal is dependent on the ratio of elastin and collagen within the tissues [18]. The handpiece applies a certain amount of pressure on the tissue to fuse. This amount of pressure is characteristic of the device used. Vessel sealant devices can achieve hemostasis without dissection of the blood vessels. This is particularly valuable when blood vessels are surrounded by fat or other tissues (e.g., an ovarian pedicle). A 5‐mm handpiece can also be used for blunt tissue dissection.
Figure 5.8 Valley Lab Force Triad generator, which combines monopolar, bipolar, and vessel sealant technology. It features three touchscreen modules. Handpieces are automatically recognized when they are plugged in.
Source: From Huhn [3].
Bipolar vessel sealant devices have been used in several organ systems, including the reproductive tract, lung, liver, and other soft tissue structures [19–22]. There are numerous generators and handpieces available for use in open surgery and MIS (Figure 5.9). Lateral thermal damage has been reported to occur between 1.5 and 6 mm from the coagulation site [13, 14, 23]. Bipolar vessel sealant technology has proven to be safe and effective for use in MIS with applications in numerous procedures, including reproductive surgery, adrenalectomy, splenectomy, nephrectomy, partial pancreatectomy, and pericardiectomy. The resulting blood vessel seals have been tested to withstand pressure well above physiologic systolic pressures [17,24–28]. Although peripheral lung biopsies have been successfully obtained in experimental studies [19], the variability of bronchus sealing makes this technique unreliable for larger biopsies [29, 30].
Figure 5.9 Valley Lab LigaSure generator with numerous bipolar handpieces for open and minimally invasive surgery. Some handpieces require foot‐pedal activation; others are handswitch activated.
Source: From Huhn [3].
Figure 5.10 A variety of bipolar handpieces are available for open and MIS. A cordless ultrasonic device is also available for use in MIS.
Source: Courtesy of Medtronic, Minneapolis, MN.
Vessel sealant device handpieces are compatible with specific generators and vary in terms of shaft length, shaft diameter (3–12 mm), and function. Commonly used LigaSure (Covidien, Medtronic, Minneapolis, MN, USA) handpieces in MIS include the Atlas, Maryland, and Dolphin Tip (Figure 5.10). The Maryland and Dolphin Tip are finer and can be used for blunt dissection in addition to vessel sealing. The LigaSure Advance and LigaSure Retractable L‐hook handpieces combine a monopolar tip with vessel sealant technology. The Caiman (Aesculap, Tuttlingen, Germany) handpieces are available in 5 and 12 mm diameters in both straight and articulating options (up to 80°). A finely curved Maryland tip is also available for tissue dissection. Enseal (Ethicon, Johnson&Johnson, Cincinnati, Ohio, USA) is also available in a variety of curved, straight, and articulating handpieces. MarSeal (KLS Martin, Tuttlingen, Germany) is designed as a reusable vessel sealant device handpiece. Similar to the other single‐use vessel sealant devices, they offer curved
