Table of Contents
Introduction
Monopolar cautery pencil is a kind of electrosurgical pencil that replaces a mechanical scalpel for tissue cutting, electrosurgery
including monopolar cautery and bipolar cautery, has been widely used in surgery for more than 70 years. It has the advantages of rapid hemostasis, less bleeding, prevention of bacterial infection, and good postoperative healing.
including monopolar cautery and bipolar cautery, has been widely used in surgery for more than 70 years. It has the advantages of rapid hemostasis, less bleeding, prevention of bacterial infection, and good postoperative healing.In this post we will discover the ins and outs of Monopolar Cautery and Monopolar Cautery Pencil, from its functions to safety tips. Let’s start it.
Components of a Monopolar Cautery
How Does Monopolar Cautery Work?
In monopolar surgery, the current flows into the body from the monopolar cautery pencil and then flows out through the disposable grounding pad. As shown below
Components
- a generator (Electrosurgical unit)
- an active electrode (Monopolar cautery pencil)
- a return electrode (disposable grounding pad）
- cables and connections
In the monopolar mode, a complete circuit is used to cut and solidify the tissue, composed of a generator, an active electrode (Monopolar cautery pencil, also know as Electrosurgical pencil), a return electrode (disposable grounding pad), cables and connections. If there is no hand control function on the cautery pencil, it is equipped with a foot controller.
), a return electrode (disposable grounding pad), cables and connections. If there is no hand control function on the cautery pencil, it is equipped with a foot controller.Definition and Types of Monopolar Cautery Pencil
Definition of Monopolar Cautery Pencil
Monopolar cautery pencil, as the active electrode, is to concentrate the high-frequency current, directly destroying the tissue under the electrode head. When the tissue or cell temperature rises to such an extent that the proteins in the cell denature, the function of CUT or COAG occurs.
Types of Monopolar Cautery Pencil: Hand control and Foot Control
According to the different control methods, the monopolar cautery pencil can be divided into hand control and foot control. Hand control electrocautery pencil generally has two function buttons, yellow for Cutting, and blue for Coaging. The shape of the button of the function button, is divided into three kinds, Elliptic, Circle, and Rocker.
generally has two function buttons, yellow for Cutting, and blue for Coaging. The shape of the button of the function button, is divided into three kinds, Elliptic, Circle, and Rocker.There is no function button on the electrocautery pen controlled by the foot, and the function button is on the host computer. According to the different plugs on the cable, the foot control electrocautery pencil is divided into a 6.3mm diameter microphone plug and a 4mm diameter single-pin plug.
is divided into a 6.3mm diameter microphone plug and a 4mm diameter single-pin plug.
Cutting Head Types of Monopolar Cautery Pencil
The monopolar cautery pencil is mostly straight, and the knife head(Electrode) can be selected according to the surgical needs of different types, such as blade electrodes, needle electrodes, ball electrodes, and so on. These can be coated with Teflon to create a non-stick cutter head that prevents the electrocautery pen from sticking to tissue during surgery*.
In addition, there is a diposable loop electrode(cutter head), made from tungsten wire. according to the shape of tungsten wire, divided into annular type, square type, flag type and B type, and so on. The tungsten gold needle tip is only exposed 3mm, melting point of up to 3400℃, and can also effectively prevent tissue adhesion during surgery.
New Type of Monopolar Cautery Pencil: with a Suction Device
At present, the monopolar cautery pencil with suction device on the electric knife pen has come out, Disposable Smoke Evacuation Pencil, which can suck the smoke, blood and seepage while cutting and electrocoagulation, and keep the clear surgical field of view.
, which can suck the smoke, blood and seepage while cutting and electrocoagulation, and keep the clear surgical field of view.
Remarks
* Different manufacturers of electrosurgical pen and knife head, because of the different designs or molds, the appearance of the shape may be different, but the overall function, buttons, and so on are the same.
* When the monopolar cautery pencil cuts human tissue, it mainly relies on the heat generated by the front end of the electrode (resistance) to complete the cutting operation. Because the composition of different tissues such as muscle, fat, and skin is different, the color and shape of the adhesive presented on the electric knife head are also very different, mostly yellow and black eschar. So anti-stick is a useful function of cautery pencils.
Definition and Types of Disposable Grounding Pad
Definition of the disposable grounding pad
In order to avoid burning the patient by continuing to heat the tissue as the current leaves the patient and returns to the monopolar cautery pencil, the disposable grounding pad in the monopolar device must have a relatively large area of contact with the patient to provide a low impedance and low current density channel. Some monopolar cautery used in doctors’ clinics have a small current and low density and can be used without disposable grounding pads, but most general-purpose monopolar cautery use a larger current, so disposable grounding pads are required.
The role of the disposable grounding pad
It can form a current loop, while reducing the current density at the disposable grounding pad, to avoid the current leaving the patient and returning to the monopolar cautery pencil to continue to heat the tissue and burn the patient.
Types of the disposable grounding pad
According to the current circuit is divided into monopolar and bipolar two types, while using monopolar grounding pad and bipolar grounding pad.
The conductor of the monopolar grounding pad is a complete piece of metal (or conductive rubber), the circuit resistance is almost 0, and the conductor of the bipolar grounding pad (also known as the split pad) is composed of two pieces of metal separated by a certain distance, after coating conductive adhesive, the circuit resistance of the plate is still large (DC resistance is several thousand ohms or more).
Because the circuit resistance of the monopolar grounding pad is almost 0, the applied detection current can only determine whether the circuit itself is broken, and can not detect the contact state with the patient.
After the bipolar grounding pad is affixed to the patient, the patient’s resistance is connected between two pieces of metal (foil), and the signal voltage (very low, <5V) can be generated when the detection current is applied to the patient. This voltage is closely related to the patient’s body impedance and the contact resistance with the plate. The detection of this signal can determine whether the patient has contact with the bipolar grounding pad and the closeness of the contact, to prevent burns.
* The bipolar grounding pad can only be used on the electrosurgical unit with the bipolar grounding pad detection function, and the electrosurgical unit without the bipolar grounding pad detection function can not be connected with the bipolar grounding pad.
The material is divided into hard grounding pad (that is, metal pad) and soft grounding pad. The hard pad can be reused, and the soft pad is disposable.
The advantages of soft disposable grounding pad are: easy to use, good adhesive performance, the guide material contains water, can increase the conductivity of the skin, but also can fill irregular skin, easy to conduct electricity, to avoid the disposable grounding pad on the patient’s burn, has been widely used, gradually replacing the traditional repeatedly used hard pad.
The Monitoring System of Monopolar Cautery
Types of Monitoring System
According to the plate monitoring system (CQMS), the monopolar mode is divided into grounded circuit (grounded) and suspended circuit (isolated).
Which is better: Grounded or Isolated?
At present, most of the clinical uses are isolated, and the only path of high-frequency current is the disposable grounding pad, and the output cutting and coagulation currents are returned from the disposable grounding pad. The output system isolated from the ground makes the current of the monopolar cautery pencil no longer need the auxiliary channel between the patient and the earth, thus reducing the risk of burning the body that may be in contact with the ground object. So the chance of a bypass burn is small.
The use of ground-based grounding, the risk of burn is greater than the isolated type of insulation output system.
How Does a Monopolar Cautery Pencil Work?
The Working Principle of Monopolar Cautery Pencil
According to the principle of medical physics, when the high-frequency current passes through the human body tissue, due to the extremely short time of each oscillating electrical pulse, the ions are difficult to cause migration, only in the viscous body fluid vibration, due to friction and heat, monopolar cautery pencil is the use of high-frequency current through the body of this thermal effect and made.
High-frequency electrical cutting, usually the use of a blade or needle electrode, the effective area is very small, and the current density in the tissue under the electrode is very large, so it can generate a lot of heat in an instant, the tissue under the electrode explosively evaporated, split into a non-bleeding, narrow and flat, a few millimeters deep incision, It can also coagulate the blood in the blood vessels to a certain depth, replace the ligation, and complete the hemostatic work of the incision.
Our usual mains frequency is 50Hz. We can also perform electrosurgery in this frequency band, but in this band, the current can stimulate the body too much and cause death. That’s how electrocution works. After the current frequency exceeds 100KHz, the nerves and muscles no longer respond to the current, so the monopolar cautery pencil is to turn the 50Hz electrical current of the mains into a high-frequency current of more than 200KHz, so that the high-frequency energy passes through the human body with minimal stimulation to the patient without any danger of electric shock.
The Functions of Monopolar Cautery Pencil
- Cutting: the cautery pencil and the tissue are separated by a thin layer of water vapor, and the short strong heat flow makes the cells become vapor, and has a little hemostatic effect;
- Coaging: the cautery pencilis in good contact with the tissue, deep coagulation spreads radially, and the relevant soft tissues become light brown eschar;
- Electrocautery: There is no contact between the cautery pencil and the tissue. The long arc first causes condensation on the surface of the tissue. With the electrocautery, the deep tissue becomes necrotic and the related soft tissue forms black hard eschar.
The Application Range of Monopolar Cautery Pencil
It is widely used in surgery, dermatology, dentistry, and can be used to cut different tissues according to its function. Patients with cardiac pacemakers are prohibited from using high-frequency monopolar cautery pencil. According to different working modes of different cautery pencil, the clinical applications are as follows:
Monopolar Cautery Cutting
- Pure cut: suitable for fine non-damage cutting of any tissue, such as: plastic surgery, burn scab cutting.
- Mixed cut: Cutting at the same time has a certain coagulation effect. It can be widely used in general surgery, thoracic surgery, orthopedics, urology and so on.
- Low voltage cutting: suitable for endoscopic surgery.
Monopolar Cautery Coagulation
- Dry hemostasis: widely used in general surgery, chest surgery, orthopedics, urology, gynecology, and so on.
- Electrocautery hemostasis: It can complete coagulation and cautery for large-area bleeding. Widely used in general surgery, chest, orthopedics, urology, gynecology, and other operations to stop bleeding.
- Low-pressure electrocautery coagulation: suitable for coagulation in fine tissue and endoscopic surgery
- Jet coagulation: suitable for large-area tissue bleeding.
For Return Electrode Bipolar Mode
As we discussed above, return electrodes are generally divided into monopolar and bipolar two types. Monopolar working mode is generally divided into pure cutting, mixed cutting, and coagulation; Bipolar is mainly used in precision surgery, the power is smaller than the single pole, the effect is more accurate, generally only two kinds of cutting and coagulation, suitable for neurosurgery and microsurgery.
Steps to Use Monopolar Cautery Pencil
1. Connect the power cable and disposable grounding pad cable.
2. Power on, boot self-test, according to the instructions and operation to choose the appropriate output power.
3. The disposable grounding pad is attached to the patient’s muscle-rich area.
4. Connect the wire of the cautery pencil and generator, and use the manual switch or foot switch.
5. After use, turn off the power switch of the host first and then unplug the power plug.
Tips of Monopolar Cautery Pencil Safety Use
– Check whether the wires are worn, broken or loose
– Do not wrap the knife and pencil lead around the metal instrument and then fix it on the operating table
– Do not wrap or tie pen lead
– When not in use, the electric knife should be placed in the protective box
– The protective box should not be made of flammable materials such as paper, plastic, etc
– The knife and pen should not be near or in contact with flammable materials
– Do not use a red catheter or other plastic material as the insulation layer of the electrode
– Use insulated cutter head approved by the manufacturer。
