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ssss1 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].

ssss1 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 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.