Biomed 101: ESU Principals, Safety and Testing

Biomed 101: ESU Principals, Safety and Testing

The concept of cautery as a medical practice has been around for hundreds of years. In ancient times, rocks heated in a fire were used to seal off wounds. Modern medical electorsurgery uses this principle of cautery, but uses heat generated by electric current rather than hot stones. The first electrosurgical unit (ESU) was invented in the early 1900s by William Bovie. The name Bovie remains widely popular in the electrosurgical industry today, and many people still refer to ESUs as Bovies.

What does an ESU do?

Electrosurgical units are used in surgical procedures for cutting and coagulating tissue. There are many applications from small units used in dermatology to remove skin lesions, to more powerful units that may be used during procedures such as open heart surgery.

Modes of electrosurgery

There are two primary modes used in electrosurgery: cut and coagulation. Cut simply uses electrical current passed through an active electrode, also referred to as a hand piece, to cut through tissue. There are two types of cut modes: blended cut and pure cut. In pure cut mode, the surgeon achieves a clean cut, very similar to an incision produced by a scalpel. In pure cut mode, there is no process to stop bleeding, also known as hemostasis. Coag, short for coagulation, is a technique used to control bleeding. In coag mode, the tissue is cauterized between contact with the hand piece. Both cut and coag may be performed at the same time using a blend setting. Blend refers to the ability to both cut tissue and simultaneously coagulate at the surgical site. Figure 1 illustrates the effects of voltage and time in different modes.

In addition to cut and coag, there are also two primary methods used to deliver energy: monopolar and bipolar operation. Monopolar uses a common return of electricity from a dispersive electrode, and is typically placed on an area of the body that allows for a larger area of current density such as the thigh or buttocks. Bipolar operation does not require the use of a dispersive electrode. In bipolar operation, the surgeon may use a hand piece that is similar to a pair of tweezers where the current is passed directly between the two points, thus heating the tissue to achieve the desired effect.

There are also multiple techniques the surgeon may use during procedure. Fulguration is one of these techniques, performed when the surgeon does not allow the active electrode to come in direct contact with the tissue. The ionization of the air between the active electrode and tissue produces a spark, giving more of a charring effect typically used for ablations where layers of tissue are destroyed with minimal bleeding. A second technique is desiccation, where the active electrode is used in close proximity or direct contact with the tissue. This causes a thermal effect in which the tissue heats up and the fluid within the tissue cells is turned into steam. This technique has deeper effect in the tissue than fulguration.

Safety is of the utmost importance when working with an ESU. The ESU units may produce small controlled sparks when in use, causing a potential fire hazard. Staff must be aware of flammable solutions, such as alcohol, that may be in the surgical field as well as the proximity to oxygen. Moistened sponges or towels should be readily available to extinguish a fire if necessary. With many units, two active electrodes may be used at once. When one active electrode is energized, the unused may be active as well. When an active electrode is not is use it needs to be holstered to prevent unintended patient burns. Another crucial step to prevent patient burns is making sure that the dispersive electrode is placed appropriately on the patient, avoiding areas that may have excessive hair, scars or bone.

As a biomedical technician, it is our responsibility to ensure all our devices are operating and within specifications. In order to accomplish this there are several standard tests that must be performed during routine preventive maintenance. Since this is a device that delivers an output to the patient it is important to test the power levels and the multiple outputs that may be available.

Here are tests that need to be performed during routine preventive maintenance:

Power Output Test – Measuring the amount of energy delivered during cut and coag modes when using the monopolar function and also the energy delivered using the bipolar functions. These energy levels need to be tested across a range of the available power settings from low to high.

Power Distribution Test – Measuring the output at multiple loads to ensure that the impedance sensing circuits are functioning properly.

RF Leakage Current Test – In this test we are measuring the amount of current that is present on the conductive surfaces of the ESU during activation of the unit. This is a critical parameter because it will indicate dielectric breakdown at the power output of the ESU and may lead to patient burns. IEC standard 60601-2-2 states that a maximum of 4.5 watts measured with a 200 ohm inductive load may not be exceeded.

Return Electrode Monitor Test – During this test we are verifying that the return electrode monitoring circuits are working correctly by applying different resistances that simulate the patient’s connection to the dispersive electrode

Conclusion

While electrosurgical units can be dangerous if used incorrectly or poorly maintained, they perform a vital function during surgical procedures. They allow quicker recovery times for patients, and can reduce the time spent under anesthesia. It is crucial that ESUs are routinely inspected and maintained to ensure the safety of patients and staff.

To learn more about electrosurgical unit preventive maintenance best practices, download the free white paper, “10 Best Practices for Electrosurgical Unit Preventive Maintenance.”

Boyd Campbell, CBET, CRES, has 28 years of experience in the biomedical field and is co-founder of Southeastern Biomedical. He possesses biomedical experience of multiple capacities, from technical to managerial. He is an active member of the North Carolina Biomedical Association and is a two-time past president of the organization. Campbell has also assisted numerous biomedical organizations by providing training and education.

This article was originally published on TechNation.