What Is Electrosurgical Unit (ESU)
An electrosurgical unit is a medical device that applies high-frequency current to perform surgical operations. Its core function is to convert ordinary electrical current into high-frequency alternating current, well beyond the response range of the human nervous system. When this current acts on biological tissue, it primarily generates thermal energy rather than electrical stimulation, thereby achieving precise cutting and effective coagulation. Based on the configuration of the electrical circuit, ESU operating modes are divided into two main types: monopolar and bipolar.
Components of the Electrosurgical Unit
Electrosurgical Generator:
The core energy source of the system, precisely generating high-frequency AC pulses. Its main functions are to adjust output power, waveform mode (cutting, coagulation, mixed), and frequency characteristics to ensure safe and effective energy delivery to the surgical electrode.
Cables:
Conductors that connect the generator to various surgical electrodes and the patient return electrode, transmitting high-frequency current.
Electrodes (ESU Pencil& ESU plate / Bipolar Forceps):
The critical instruments for delivering current to the target tissue. The active electrode (electrosurgical pencil) applies energy directly to the surgical site. In monopolar mode, the patient return electrode (grounding pad) establishes a low current density return path to safely disperse current back to the generator. Bipolar forceps integrate both output and return paths within the same surgical instrument, with the two tips functioning as the active and return electrodes.
Footswitch/Controller:
The main human-machine interface that gives surgeons immediate, precise control over energy output. Current can be activated or stopped instantly via a foot pedal or hand switch, enabling dynamic adjustments during different surgical stages while allowing both hands to remain focused on the operative field.
Working Modes and Corresponding Accessories
Monopolar Mode
Monopolar Cutting:
Uses continuous current to quickly incise tissue, similar to slicing butter with a hot knife, producing only minor thermal spread to surrounding areas. Commonly used for dividing large tissue masses, such as muscle or viscera separation.
Monopolar Coagulation:
Applies pulsed current to heat and coagulate tissue, mainly for controlling widespread surface bleeding. The current penetrates deeply, sealing microvessels at greater depths—ideal for managing diffuse deep bleeding.
Accessories: Electrosurgical Pencil & Return Electrode
The electrosurgical pencil is the surgeon’s handheld “surgical pen,” with its tip directly contacting tissue to deliver energy. The return electrode functions like a safety ground, typically adhered to the patient’s skin to complete the circuit. Modern self-adhesive pads greatly reduce the risk of skin burns.
Bipolar Mode
Bipolar Standard Coagulation:
Current flows only between the two tips of the bipolar instrument, with heat concentrated in the tissue grasped by the forceps. This is particularly suited for neurosurgery and other procedures requiring extreme precision in hemostasis.
Fine Coagulation:
Uses highly refined control to limit thermal effects to extremely thin layers, making it perfect for delicate surgeries such as retinal detachment repair or middle ear reconstruction, minimizing tissue carbonization and thermal spread.
Bipolar Cutting:
Through improved electrode design, tissue can be cut directly while simultaneously coagulating, enabling “cut-and-coagulate” operations in confined spaces like the nasal cavity or larynx.
Accessories: Bipolar Forceps
These special forceps have two tips that serve as the output and return electrodes. Non-stick materials reduce tissue adhesion, and varied angled designs suit different precision procedures. Some models also feature irrigation capability.
**Ligasure Mode** (Available on Some Advanced Units)
Uses intelligent tissue sensing and unique energy waveforms to fuse and seal vessel walls, achieving closure strength far exceeding standard coagulation techniques.
Accessory: Sealing Forceps
Specialized forceps integrating pressure sensing and energy control, capable of automatically detecting vessel thickness and moisture, sealing vessels up to 7 mm in diameter. Frequently used in gastrointestinal surgery for vascular bundle management.
Advantages of Electrosurgical Machine
1. High-frequency current achieves immediate coagulation upon tissue contact, sealing microvessels and capillary ends through protein coagulation. This significantly reduces intraoperative bleeding and leakage, greatly improving surgical field visibility.
2. Output can be finely adjusted to watt-level increments. In bipolar mode, tissue targeting is at millimeter precision. Intelligent generators integrate real-time tissue impedance feedback, with millisecond-level response ensuring energy release matches tissue status—protecting nearby nerves, vessels, and delicate structures.
3. The precise heat effect minimizes surrounding tissue injury, shortening the inflammatory repair phase. Uniform protein coagulation layers formed by ESU can re-epithelialize by day 3 post-operation, reducing wound healing time by ~30% compared to conventional instruments.
4. Combines cutting, coagulation, ablation, vaporization, and vessel sealing in a single platform. Mode switching allows adaptation to different tissue types (vascular, neural, adipose, muscular) without changing instruments—boosting efficiency by ~30% in endoscopic surgeries.
Types of High-Frequency Electrosurgical Units
Basic Electrosurgical Unit
Integrates standard cutting and coagulation for general use, suitable for general surgery, orthopedics, breast surgery, and other common procedures. Delivers reliable performance for routine cases such as superficial mass excision or orthopedic debridement.
Function-Enhanced Units
Adds specialized modules to meet advanced clinical needs in specific fields.
LEEP Unit (Loop Electrosurgical Excision Procedure)
Designed for cervical lesion treatment, using a loop-shaped electrode and controlled current to precisely remove abnormal cervical tissue. Heat damage is limited to ~1.5 mm depth, enabling complete lesion excision while preserving specimen margins—ideal for targeted diagnosis and treatment of precancerous cervical lesions.
Argon Electrosurgical Unit
Uses ionized argon gas to achieve non-contact hemostasis. The argon plume evenly coats the wound surface, forming a deep coagulation layer (~3 mm depth) to control diffuse bleeding in parenchymal organs like the liver and spleen. Especially valuable for large surface wounds or areas not amenable to direct compression, playing a critical role in thoracic and laparoscopic surgery.
Frequently Asked Questions
How does electrosurgery work?
The generator produces high-frequency alternating current, delivering electrical energy to the surgical instrument tip. When the instrument contacts or approaches tissue, the current passes through the tissue’s resistance, generating localized heat. This heat can instantly vaporize and separate cells (cutting) or denature proteins to seal vessels (coagulation), enabling precise and controllable tissue management.
What’s the difference between electrocautery and electrosurgery?
Electrocautery is an early single-purpose technique (surface burning only), whereas modern electrosurgery is a multifunctional integrated system:
· Electrocautery uses low-voltage DC current for superficial tissue carbonization.
· Electrosurgery uses high-frequency AC current (>200 kHz) with controlled modes for cutting, coagulation, and mixed effects.
· The key differences lie in current characteristics and functional versatility.
What’s the difference between monopolar and bipolar cautery?
· Monopolar: Current flows from the active electrode (e.g., electrosurgical pencil) to the target tissue, through the patient’s body to the return pad—providing wide energy spread, suitable for deep cutting and large-area coagulation.
· Bipolar: Current is confined between the two tips of a forceps, delivering precise energy for fine hemostasis and work in nerve/vessel-dense areas.
What’s the difference between cutting and coagulation modes?
· Cutting: Continuous high-frequency current vaporizes intracellular fluid instantly, creating a linear incision with minimal thermal damage (~0.1 mm)—ideal for rapid dissection.
· Coagulation: Intermittent pulsed current causes collagen contraction and protein cross-linking, sealing vessels without tissue separation, with deeper thermal penetration (~0.5–2 mm).
What safety precautions are needed in electrosurgery?
Key safety measures include:
① Circuit Safety: Ensure return pad is securely applied to a muscle-rich area in monopolar cases (avoid bony prominences, scars, hair).
② Contact Management: Prevent instruments from touching metallic implants or monitoring electrodes.
③ Power Matching: Adjust output based on tissue type (fat, muscle, tumor).
④ Smoke Control: Continuously evacuate surgical smoke to prevent viral/particulate spread.
⑤ Equipment Maintenance: Regularly check insulation integrity of instruments.
⑥ Risk Avoidance: Avoid use in combustible gas (e.g., bowel lumen) or oxygen-rich environments.