Principles of Principles of electrosurgery electrosurgery Dr. HOSSAM HUSSEIN
Nov 28, 2014
Principles ofPrinciples ofelectrosurgeryelectrosurgery
Dr. HOSSAM HUSSEIN
Its all about Its all about HEATHEAT
Electrosurgery uses heat to achieve desired effect
Operator must optimise heating effect
Operator must minimise risk
ElectricityElectricity
Electron: tiny –ve charged particle Circuit: path electrons flow round Current: rate of flow (Amps) Voltage: force of flow (Volts)
Properties of Electricity
CURRENT = Flow of electrons during a period of time, measured in amperes
CIRCUIT = Pathway for the uninterrupted flow of electrons
VOLTAGE = Force pushing current through the resistance, measured in volts
RESISTANCE = Obstacle to the flow of current, measured in ohms (impedance = resistance)
ElectrosurgeryElectrosurgery
Current and voltage provided by generator
Circuit: passes through patient
Tissue provides resistance and produces heat
Tissue effectTissue effect
The amount of heat and effect on tissue depends on:
1. Current (amps)2. Voltage3. Duration of application 4. Modulation of flow5. Tissue contact (focus of the instrument
applying the electricity)
Amps and VoltsAmps and Volts1. Current (amps)
2. Voltage
3. Duration of application
4. Modulation of flow
5. Tissue contact
Power (watts) is determined by current and voltage:
Watts = Amps x Volts
Tissue effect depends on Power Relationship between amps and volts
DurationDuration
Tissue death 45oC
Coagulation 70oC
Carbonisation 200oC
Vaporisation 100oCDesiccation 90oC
1. Current (amps)
2. Voltage
3. Duration of application
4. Modulation of flow
5. Tissue contactT
empe
ratu
r e
0
50
100
150
200
250
300
0 sec 10 sec 20 sec 30 sec 40 sec 50 sec
Temperature over time
cut
Electrosurgical generators are able to produce a variety of electrical waveforms. As waveforms
change, so will the corresponding tissue effects. Using a constant waveform, like “cut,” the surgeon
is able to vaporize or cut tissue. This waveform produces heat very rapidly.
coagulation
Using an intermittent waveform, like “coagulation,” causes the generator to modify the waveform so
that the duty cycle (on time) is reduced. This interrupted waveform will produce less heat. Instead
of tissue vaporization, a coagulum is produced.
blended current
A “blended current” is not a mixture of both cutting and coagulation current but rather a
modification of the duty cycle. As you go from Blend 1 to Blend 3 the duty cycle is progressively
reduced. A lower duty cycle produces less heat. Consequently, Blend 1 is able to vaporize tissue with minimal hemostasis whereas Blend 3 is less effective at cutting but has maximum hemostasis.
ModulationModulation
-15
0
15
-16
-1
14
“Cut” = continuousUnmodulated wave form
“Blend ” = Modulated wave formBlend 1: 50% on 50% offBlend 2: 40% on 60% offBlend 3: 25% on 75% off
-16
-1
14
“Coagulation” = 5%:95%Modulated wave form
1. Current (amps)
2. Voltage
3. Duration of application
4. Modulation of flow
5. Tissue contact
Low voltage
High voltage
InstrumentationInstrumentation1. Current (amps)
2. Voltage
3. Duration of application
4. Modulation of flow
5. Tissue contact
Power (Amps X Volts)Power (Amps X Volts)1. Current (amps)
2. Voltage
3. Duration of application
4. Modulation of flow
5. Tissue contact
Use of electricity in practiceUse of electricity in practice
Diathermy:
Diathermy means the use of electricity to generate heat. In surgery it is used to vaporise tissue for cutting purposes or to coagulate it to effect haemostasis or destroy tissue. The electricity has to be of high frequency,
usually referred to as radio-frequency
Electrical circuitsElectrical circuits
PatientPatientGeneratorGenerator
Diathermy Diathermy equipmentequipment
Direct current
Direct current and Alternating current
Direct current: electricity that flows in one direction only It is used in “cautery”.
A current is passed through a wire, heating it. The hot wire could then be used to cut or destroy tissues
Alternating current:
electricity that alternately flows one way and then the other. Household electricity is alternating current.
The frequency of the changes in direction of flow is 50 cycles per second.
Diathermy uses vastly higher frequencies The unit of frequency is the “Hertz”. 1 Hz = 1 cycle per second. The high frequency, is referred to as radio-frequency , because it falls into the range of frequencies used for
wireless transmissions
Heinrich HertzHertz lived from 1857 to 1894 and was the first to demonstrate experimentally the production and detection of Maxwell‘s waves. This discovery of course lead directly to radio.
One of the main values of the high frequency is that it is too fast to stimulate nerve fibres.
This means that you don’t get spasm or paralysis of
muscle. To avoid these unwanted effects, you need
frequencies greater than 100 kHz. Diathermy units use frequencies from 500 kHz
(500,000 cycles per second) to 2 MHz (2 million cycles per second).
Monopolar circuitsMonopolar circuits
this is the type of diathermy that is most often used in surgery, including open, minimally invasive, colposcopic and hysteroscopic
Monopolar circuitsMonopolar circuits
Earth
• Classic system• Risk of return
injury• Surgeon• Patient
Isolated system
Monopolar circuitsMonopolar circuits
Uni-monopolar
• Monitored returnSplit Return plate
Monopolar circuitsMonopolar circuits
• Hysteroscopic surgery• Non-ionic irrigation fluid
and risk of fluid overload
• Laparoscopic surgery• Risk of bowel injury
from return of electricity to generator
Monopolar circuitsMonopolar circuits
Bipolar circuitsBipolar circuits
Generator
+
-
• Bipolar circuits• Minimal lateral damage
Bipolar
• Bipolar circuits• Impedance control
Resistance to flow increases Resistance to flow increases with tissue desiccation and with tissue desiccation and
is detected by the generator is detected by the generator stopping the currentstopping the current
Bipolar circuitsBipolar circuits
•Direct coaption of vessel walls with handpiece
•Heat produced by electrical resistance denatures vessel wall proteins to
create seal
•Generator responsive to electrical impedance
•Power output modified to optimise haemostasis through tissue desiccation without charring
Second generation Second generation methods of haemostasismethods of haemostasis
• Bipolar circuits, 2nd generation• Ligasure• Tripolar
• Non-electrical methods may use sonic vibration to denature vessel wall proteins with little heating effect
Second generation Second generation methods of haemostasismethods of haemostasis
Lowest power and lowest Voltage to achieve tissue effect
Bipolar vs monopolar
Awareness of electrical circuit (return of electricity to generator)
SafetySafety
Place electrode in sheath when not in use
Avoid monopolar with cardiac pacemaker
Return plate Split plate Away from artificial joint Away from scar or bony prominence
SafetySafety
Direct coupling and Capacitive coupling.
Direct injury (field of view)
SafetySafety
• Direct coupled injury
Metal retractorMetal retractor
SafetySafety
Direct coupling and Capacitive coupling cont.,
There are two, circular, conductive plates with a wire attached to each.
They are separated by a gap. The magical thing about a capacitor is the
ability of an alternating current in one side of the device to induce an alternating current on the other side .
• Capacitance coupling
SafetySafety
Surgical smoke Poor view Risk to theatre staff
SafetySafety
Insulation failure
SafetySafety
THANKS
Methods of endometrial ablationNd-YAG Laser ablationEndometrial resectionCryosurgeryMicrowave destructionThermal coagulation
Ablation methodsLaser ablation Nd:YAGLoop resection.Rollerball electrode (2.5 mm)Ball end electrode.Radio-frequency ablation (RaFEA)Microwave ablationUterine thermal balloon (Gynecare,
Thermachoice & Cavaterm).
Thermal balloon ablation
Easy to learn Less time consumingHigh success rateNo risk of fluid overloadSuitable for cardiac, respiratory, renal
cases (suffer much from fluid overload)
LASER INSTRUMENTATION
Laser energy can be delivered to tissue in a variety of ways: by contact or from a distance, in conjunction with an operative microscope, through an endoscope or with the aid of freehand tools.
dry and clear field, even when operating in an environment of high vascularity.
The reasons for this impressive procedural variety and wealth of benefits lie in the particular properties of the laser as a special source of energy
Physical effects of laser on tissue
The laser effect on a tissue sample is one of transmission, reflection, scattering or absorption.
Physical effects of laser on tissue
The effect on tissue achieved by any laser commonly used in therapeutic medicine is a consequence of its absorption therein. In particular, the energy deposited by most of the commonly used lasers is transformed into heat, thereby obtaining a thermal effect on the tissue. The types of lasers used in therapeutic medicine are confined to the visible, ultraviolet and infrared regions of the spectrum.
Physical effects of laser on tissue
CO2 laser
CO2 laser radiation is readily absorbed by the first few cellular layers of tissue, constituting the first 100 μm. Consequently, this is a laser used for superficial treatments.
Nd :YAG
The neodymium: yttrium–aluminum–garnet (Nd :YAG) laser features a wavelength of 1.06 μm (near infrared). Water is completely transparent to this type of radiation. Consequently, the Nd :YAG laser is ideal for the treatment of lesions located in liquid-filled cavities, such as the bladder and the uterus (filled with a distension liquid). The Nd:YAG laser is, however, strongly scattered by the tissue. Penetrating beams are scattered and folded at multiple sites, increasing the effective path length of the beam through the tissue. Nd :YAG laser light, which is absorbed to some degree by the proteins within the tissue bed, deposits energy each time absorption takes place. The end result is the creation of a deep and laterally extended ball of affected tissue, 3–5 mm in diameter.
Thermal effects on tissue
It is noteworthy that the coagulation process induced by the CO2 laser is rather different from that effected by the Nd :YAG laser. Shrinkage of the capillary vessel caused by the CO2 laser is a result of vaporization of the watercontained in the walls of the blood vessel. If, however, the CO2 laser beam hits a vessel, it is readily absorbed by the liquid blood at its exit from the initially desiccated wall. Thus, it will never have the chance to hit the opposite wall, leaving the vessel open and, thereby, causing extensive bleeding. Hence, it is important to remember that the sharply focused beams of CO2 lasers are inadequate for the treatment of highly vascular tissue.
Conversely, Nd :YAG lasers are unhindered by the presence of the liquid medium; consequently, they can very effectively accomplish complete coagulation of the bulk of the tissue. Nd :YAG lasers are excellent coagulators.
Energy, power and power density
Energy, power and power density are the physical parameters that determine the eventual rise in temperature.
Energy is measured in joules. Power is the amount of energy delivered per second and is measured in watts (joules/s). The thermal effect of the laser is local.
Thus, the physical quantity which governs the thermal response of the tissue is the amount of power delivered to a unit of area; this quantity is called power density, and is measured in W/cm2.
FIRST-GENERATION ENDOMETRIAL
ABLATION TECHNOLOGIES Photocoagulation of the endometrium
(ND-yag) Electrocoagulation by the resectoscopic
loop electrode and subsequently by the rollerball electrode (REA).
Transcervical resection of the endometrium The uterus is distended with an electrolyte-free sterile solution (glycine, sorbitol, dextrose, etc.), and the endometrium is coagulated or resected using an electrode connected to a high-frequency electrosurgical generator.
Classification of second-generation endometrial
ablation technologies (SEATs) Hot liquid balloons
ThermaChoice® I, II and III Cavaterm™ and Cavaterm™ plus Thermablate™
Hydrothermablation (HTA) Cryoablation (Her Option®) Microwave endometrial ablation (MEA™) Impedance-controlled ablation
(NovaSure™)
ThermaChoice® II hot water balloon system
The Cavaterm™ hot glycine balloon
Hydro ThermAblator hot free saline system
The microwave endometrial ablation (MEA™) system
ENDOMETRIAL ABLATION
Endometrial ablation is the destruction or elimination of the endometrium by coagulation, freezing or resection, offered as an alternative to hysterectomy