Electrosurgery - HOSSAM

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



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



5. Tissue contact

Low voltage

High voltage

InstrumentationInstrumentation1. Current (amps)

2. Voltage



5. Tissue contact

Power (Amps X Volts)Power (Amps X Volts)1. Current (amps)

2. Voltage



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.

http://inventors.about.com/library/inventors/bl_James_Maxwell.htm

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


Earth

• Classic system• Risk of return

injury• Surgeon• Patient

Isolated system


Uni-monopolar

• Monitored returnSplit Return plate


• Hysteroscopic surgery• Non-ionic irrigation fluid

and risk of fluid overload

• Laparoscopic surgery• Risk of bowel injury

from return of electricity to generator


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.


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.


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

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Electrosurgery - HOSSAM