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Hon. Assistant prof. KSU Definition & History
Principles of Electro surgery
ES effects on tissues & Clinical Application
Types of Electro surgery.
Potential Hazards of ES
Safety Precautions OUTLINE Definition ... Heat therapy known since antiquity
“Heat cures when everything fails” …Hippocrates.
Albucasis (980BC) used hot iron to stop bleeding.
Then followed use of electrical current on a metallic element. History History Earliest recorded use of this technology was by Arsenne d Arsonval in1893.
However extensive use of electro surgery in brain surgery by Harvey Cushing & William T. Bovie and their publication in 1925 promoted Electrosurgery.
They described three distinctive effects:
Coagulation Electrosurgery refers to the cutting and coagulation of tissue using high frequency electrical current Basic Principles of Electro-surgery Electrical current is created by the movement of electrons;
Voltage is the force that causes this movement.
There are two types of electrical current:
Direct current (DC), where the electrons always flow in the same direction (eg, simple battery),
Alternating current (AC), where the current changes direction periodically (eg, electrical wall outlet). Each time an AC current reverses direction is considered one cycle;
Frequency refers to the number cycles in one second and is measured in hertz (Hz). The human nervous system is very sensitive to low-frequency (0 Hz to about 1000 Hz) electricity, due to the fact that the nervous system is in itself a complex web of electrical circuits.
Application of low-frequency electricity stimulates the nervous system causing electric shock which may involve acute pain, muscle spasms, and/or cardiac arrest. The sensitivity of the nervous system to electricity decreases with increasing frequency .
At frequencies above 100 kHz,electricity does not stimulate the nervous system.
To avoid electric shock, electrosurgical equipment operates in the frequency range of 200 kHz to 5 MHz... Electrosurgical unit components ... 1- the generator .
2- active electrode .
3- return electrode . Hence the Patient plate should be as large as possible.
It should be applied to a wide area of electrically more conductive tissues like muscles. Current does not flow uniformly to the patient plate.
Its density is higher at the corners and edges of the patient plate nearer to the active electrode.
Hence the patient plate should be placed such that the longer edge points to the active electrode. mode ... Electro-surgery can be performed using either a monopolar or a bipolar instrument. In monopolar surgery, electrical current goes through the patient to complete the current cycle, while in bipolar surgery, the. monopolar instrument. The magnitude of the current induced depends on the proximity and insulation of the two conductors and the amount and duration of voltage used . In bipolar surgery, the current only goes through the tissue between the two electrodes of the instrument. Bipolar electrosurgery is ideal when dealing with vascular areas or large blood vessels, such as the uterine artery. Current effects on tissue . Fulguration .
Vaporization/Ablation . Fulguration and vaporization are non-contact methods of monopolar electrosurgery, while desiccation/coagulation is a direct contact method of monopolar electrosurgery. Fulguration is caused by an interrupted current (coagulation mode), causing slower tissue heating and less focused tissue effect. The coagulation mode on the electrosurgical unit generates an interrupted, high voltage current dispersed over a large surface area. The coagulation mode is better suited for fatty tissue and scar tissue and when fulgurating a large surface area with superficial bleeding. Vaporization results from rapid heating in the cut mode with intense vibration and heat within the cells, which causes the cell to explode and form smoke (plume). Cutting and coagulation currents The surgeon chooses the output setting for the ESU.
The main settings are :
Blind . The cut mode on the electrosurgical unit generates a continuous, low voltage current concentrating the energy over a small area. Combines both cutting and coagulation currents
Has properties of both currents depending on setting
Blend 1: 50% on, 50% off
Blend 2: 40% on, 60% off
Blend 3: 25% on, 75% off
Higher blend number = more coagulation BLEND CUTTING .. The cutting mode results in more rapid tissue heating than the coagulation mode. If tissue is heated rapidly, the oscillation of the AC current causes intense vibration and heat within the cells, which leads them to explode and form smoke (plume). This is called vaporization and is the mechanism whereby tissue is cut .
To cut tissue, the tip of the electrode is held very near to the tissue, but not in direct contact, to concentrate current at the tip. The cut mode is preferred when thermal spread is undesirable, such as when the electrosurgical device is in close proximity to vital structures. Coagulation The cutting mode results in more rapid tissue heating than the coagulation mode. If tissue is heated rapidly, the oscillation of the AC current causes intense vibration and heat within the cells, which leads them to explode and form smoke (plume). This is called vaporization and is the mechanism whereby tissue is cut . To cut tissue, the tip of the electrode is held very near to the tissue, but not in direct contact, to concentrate current at the tip. Complications of electrosurgery Unintended burns
By one of these mechanisms :
1- Direct coupling .
2- Capacitive coupling .
3- Insulation failure . Direct coupling results from inadvertent contact of two non -insulated instruments (such as a metal trocar and a metal grasper).
Electrical current flows from the primary to the secondary instrument, which acts as a second conductor. This can lead to severe injury if the second conductor is in contact with bowel or other sensitive structures. A Capacitor is defined as two nearby conductors separated by a non-conducting medium.
A prime example of a capacitor would be monopolar scissors with an insulation layer placed through a metal cannula. The
alternating current flowing through the scissors induces unintended stray current in any conductor in close proximity with the monopolar instrument. Insulation failure results from breakdown of the insulation covering the shaft of the active electrode.
This can happen during the sterilization process or during the surgical procedure. These defects are not rare .
Insulation failure can also occur from inappropriate repeated use of disposable equipment. Smoke plume The smoke plume generated by electrosurgical destruction of tissue contains potentially toxic substances.
In high concentrations :
can irritate the eyes and respiratory tract of any individuals in the operating room, can even transmit viruses. Monopolar surgery :
Use lowest possible power setting
Use a low voltage waveform (cut)
Use brief intermittent activation
Do not activate in open circuit
Do not activate in close proximity or direct contact with another instrument Bipolar surgery
Terminate current at the end of vapor phase
Apply current in pulsatile fashion LigaSure vessel sealing system This system applies a precise amount of bipolar energy & pressure to fuse collagen & elastin within the vessel walls -permanent seal that can withstand 3 times normal systolic pressure & seals vessels up to 7 mm .
Sealing achieved w minimal sticking & charring .
Thermal spread --- apx 2 mm
The generator uses a feedback controlled response.
Used in open & laparoscopic surgery.
Disadvantage is the cost ….. Disposable
Non-disposiable devices have been introduced w promising initial results Plasma kinetic tissue management system It employs advanced bipolar tech .
This system delivers pulsed bipolar energy thro the instrument to tissues, allowing intermittent tissue cooling which limits lateral thermal spread & tissue sticking .
It has an instrument identification feature that automatically detects the optimal setting for specific instrument , as well as impedance monitor with visual & audible tissue impedance indicators.
The system has 2 different modes , the vapor pulse coagulation mode & the plasma kinetic tissue cutting mode. Tissue link floating ball A saline-cooled high-density monopolar probe used for dissection & coagulation.
Prevent tissue charring
It achieves a greater depth of tissue coagulation & hemostasis compared w ES without cooling .
Smoke forming & tissue sticking is reduced
Can be used in open & laparoscopic surgery
Mainly used in hepatic & pulmonary surgery < 40 0 less reversible thermal damage
45 C necrosis
70 C coagulation
90 C desiccation
100 C vaporization
> 100 C carbonization (charring ) Key temp points