Which of the following is the most commonly used ESU mode in surgery? A Guide to Monopolar Electrosurgery

September 30, 2025 •

3 min read

Monopolar electrosurgery is the most commonly used ESU mode in surgery, relied upon in over 80% of surgical procedures for its versatility and effectiveness. This mode utilizes a high-frequency electrical current to precisely cut or coagulate tissue, which significantly minimizes blood loss and speeds up operating times.

Quick Summary

This guide examines the fundamental principles of electrosurgical units (ESUs) by comparing the differences between monopolar and bipolar configurations. The text highlights why the versatile monopolar mode is used most often for cutting and coagulation, detailing its functionality and important safety considerations during surgical procedures.

Key Points

Monopolar is the most common configuration: The monopolar setup, which requires a dispersive grounding pad, is the most frequently used ESU mode due to its versatility.
Monopolar offers multiple tissue effects: Using different waveforms, monopolar electrosurgery can perform cutting (dissection), coagulation (stopping bleeding), and a blend of both.
Bipolar provides enhanced safety: The bipolar mode, which confines the current between two electrodes on the same instrument, minimizes thermal spread and is safer for delicate tissues or patients with pacemakers.
Cut vs. Coag depends on the waveform: A continuous, low-voltage waveform creates the precise cutting effect, while an intermittent, high-voltage waveform causes the slower, more controlled coagulation effect.
Safety is paramount: Correct placement of the dispersive electrode in monopolar mode and careful technique are critical to prevent burns and other complications.
Electrosurgery is not electrocautery: The two are different techniques; electrosurgery passes current through the patient, while electrocautery uses a heated probe and does not.

Understanding the Electrosurgical Unit (ESU)

An electrosurgical unit (ESU) generates a high-frequency electrical current to cut, coagulate, or blend tissue. The current passes through the patient via electrodes, creating localized heat at the surgical site due to the tissue's resistance. ESUs are vital in modern surgery for precision and reduced invasiveness compared to traditional methods. There are two primary ESU configurations: monopolar and bipolar, differing in how the current flows through the patient.

The Most Commonly Used ESU Mode: Monopolar Electrosurgery

The most commonly used ESU mode is monopolar. This mode is favored for its versatility across large surgical areas. In monopolar electrosurgery, the current flows from the ESU to an active electrode, through the patient's body, and returns to the generator via a dispersive return electrode or grounding pad placed on the skin.

Applications and Advantages of Monopolar

Versatility: One monopolar instrument can perform various tasks like cutting and coagulation.
Effectiveness: It is effective for rapid dissection and controlling bleeding over large areas.
Control of Bleeding: Coagulation during cutting helps reduce blood loss.

Sub-Modes within Monopolar Electrosurgery

Monopolar ESUs offer different modes for various tissue effects:

Cut Mode: Uses a continuous, low-voltage waveform for precise incisions with minimal thermal damage.
Coagulation (Coag) Mode: Employs an intermittent, high-voltage waveform to heat tissue slowly, causing dehydration and protein denaturation to seal vessels and stop bleeding.
Blend Mode: Combines cut and coag waveforms for simultaneous cutting and coagulation.
Fulguration: A non-contact coagulation technique using a high-voltage arc for superficial coagulation.

Comparison: Monopolar vs. Bipolar Electrosurgery

Bipolar electrosurgery is also commonly used, particularly when precision and safety are critical. In bipolar mode, both electrodes are on the same instrument, such as forceps, limiting the current flow to the tissue between the tips. This reduces the risk of stray current and burns to surrounding tissues.

Here is a comparative overview of the two modes:


Feature	Monopolar Electrosurgery	Bipolar Electrosurgery
Current Path	Flows through the patient's body to a distant grounding pad.	Flows only through tissue between instrument tips.
Surgical Area	Suitable for large surgical fields, offering greater versatility.	Confined to a smaller, more precise area.
Risk Profile	Higher risk of unintended burns from misplaced pads, capacitive coupling, or insulation failure.	Significantly reduced risk of burns and complications due to localized current path.
Patient Safety	Requires meticulous placement and monitoring of the grounding pad.	Preferred for patients with implanted electronic devices to avoid interference.
Applications	General surgery, endoscopic procedures, laparoscopic surgeries, cutting through dense tissue.	Neurosurgery, ophthalmic surgery, procedures requiring fine, controlled hemostasis.

Bipolar Mode in Specific Cases

Bipolar electrosurgery is preferred in several situations:

Patients with Pacemakers: To avoid interference with implanted devices, bipolar is safer as the current path is localized.
Wet-Field Surgery: Bipolar works well in fluid-filled environments.
Delicate Tissues: For procedures involving nerves or small vessels, bipolar's limited thermal spread enhances safety.

The Role of Safety and Training

Proper training and adherence to safety guidelines from organizations like AORN are essential for both modes. Key safety practices include using the lowest effective power, ensuring correct grounding pad placement for monopolar, and maintaining equipment.

Conclusion: The Dominance of Monopolar

Monopolar is the most commonly used ESU mode due to its versatility and effectiveness in various procedures. While bipolar offers a safer option for specific, delicate applications, monopolar's ability to provide both cutting and coagulation over large areas makes it a primary tool in surgery. Understanding both modes, their uses, and safety measures is vital for optimal patient care.

The Importance of Correct Terminology

It is important to distinguish electrosurgery from electrocautery. Electrocautery uses a heated probe with direct current for coagulation only, without current passing through the patient. Electrosurgery uses high-frequency alternating current passing through the patient for both cutting and coagulation. Using correct terminology is crucial for clear communication and proper equipment use.

Frequently Asked Questions

The main difference is the path of the electrical current. In monopolar mode, the current flows through the patient's body to a distant return pad. In bipolar mode, the current flows only through the tissue grasped between the two tips of the instrument.

Bipolar mode is preferred in cases requiring more precision and safety, such as during surgery on very delicate tissues, in procedures involving fluid, or for patients with implanted electronic devices like pacemakers.

Incorrect or insufficient contact with the monopolar grounding pad can cause the electrical current to concentrate in unintended areas, leading to severe patient burns.

The most common tissue effects are cutting, where tissue is vaporized to create an incision, and coagulation, where tissue is desiccated to seal blood vessels and stop bleeding.

Blend mode combines the cutting and coagulation waveforms, allowing a surgeon to simultaneously cut tissue and achieve a degree of hemostasis during the incision.

No, they are different techniques. Electrosurgery uses a high-frequency alternating current that passes through the patient to produce a tissue effect. Electrocautery uses a direct current to heat a probe tip, which then passively cauterizes the tissue without the current entering the patient's body.

Monopolar is versatile because a single active electrode can be used with various waveforms (cut, coag, blend) to achieve different tissue effects over a large area, making it suitable for many different surgical procedures.