This document discusses the principles and types of diathermy. It begins by defining diathermy and its history of development. It then describes the principle that heat is generated when electrical current passes through tissue. The document outlines the different types of diathermy including monopolar, bipolar, and modes like cut, coagulate, and blend. It discusses diathermy hazards, safety precautions for use, and advanced energy devices like bipolar electrosurgery and harmonic scalpels.

1. DIATHERMY PRINCIPLE AND TYPES
• Presenter : Dr. Annush Tha
• Moderator: Dr. DA/DB/GA
• Department of Surgery
• Pokhara Academy of Health Sciences
• 2077-07-23

2. Learning objectives
• Principles of diathermy
• Types of diathermy
• Effects of diathermy
• Complications
• Safety measures
• Advanced energy devices

3. Diathermy
• Coined by German physician Karl Franz Nagelschmidt
• Derived from Greek word – “Dia” –through and “therma” – heat
• William T. Bovie developed the first electrosurgical device –Harvard
university
• 1926- First use of Electrosurgery “ to remove mass form patient’s
head”- By Harvey Cushing
• Cushing in 1928 published a series of 500 neurosurgical procedures
using electrocautery developed by Bovie
• Then onwards electrosurgery and electrocautery became the
important tool in operating room

4. Principle of diathermy
• When an electrical current passes through a conductor- some of its
energy appears as heat—produces temperature up to 1000°C but
1cm away from tip Temperature - <38°C
• The heat produced depends upon :
• The intensity of the current
• The wave form of the current
• The electrical property of the tissues through which the current passes
• The relative sizes of the two electrodes
• Mechanism :
• Q(heat in joules)= I2 (current density)* R(resistance)* t(time)

5. Electrosurgery Electrocautery
UsesAlternating Current Uses Direct Current ( electrons flow in only one
direction)
the patient is included in the circuit and current enters
the patient’s body.
current doesnot enter the patient’s body
Only the heated wire comesin contact with tissue

6. The electrosurgical generator is the source of
the electron flow and voltage
The circuit is composed of the
• Generator
• active electrode
• patient
• patient return electrode( passive /dispersive)
Pathways to ground are numerous but may
include the O.R. table, stirrups, staff members
and equipment
The patient’s tissue provides the impedance,
producing heat as the electrons overcome the
impedance

7. Frequency Spectrum
• Standard electrical current alternates at afrequency of 60 cycles per second
(Hz)
• current transmitted through body tissue at 60 cyclescausesexcessive
neuromuscular stimulation and perhaps electrocution
• nerve and musclestimulation ceaseat 100,000 cycles/ second(100 kHz)
• electrosurgery canbeperformed safelyat “radio” frequencies above100 kHz
• An electrosurgicalgenerator takes 60 cyclecurrent and increasesthe
frequency to over 200,000 cyclesper second
• surgicaldiathermyuses frequencyin rangeof400kHz -10MHz

9. Types of diathermy
Monopolar diathermy
• Most commonly used circuit
• Dispersive pad placement:
• On shaved skin
• Contact of at least 70cm2 , preferably
more than twice the areaminimizes
current density and heat
• Avoid bony prominences, scar, metal
prosthesis, areas distal to tourniquet
• Use: cut, coagulation and blend

10. Bipolar Diathermy
No dispersive plate needed
Low power used
Advantage
Avoids lateral spread of thermal
injury
Effective coagulation
Disadvantage
Can’t cut
Doesn’t work when hemostat has
grasped the vessel and buzzed

11. Modes in diathermy
• Cut
• Generates continuous/unmodulated
• low voltage current
• Concentrates energy at a small area( high current
density)
• Rapid heating
• Oscillation of alternating causes intense vibration
and heat with in cells
• Causes cell explosion and form smoke( plume)
• Cuts the tissue by vaporization
• Tip of the electrode to be held very near to tissue
not direct contact
Cut
Low voltage
waveform
100% duty
cycle

12. Coagulation
• Generates interrupted(modulated)
• High voltage current
• Dispersed over large surface area(low current density)
• Modulated current allows tissue to cool slightly-
heating is slower
• Causes dehydration effect (loss of cellular fluid and
protein denaturation)resulting in coagulation
• Modulated current require high voltage for
dehydration
• Increases the risk of tissue damage, thermal spread
and potential complication
Coag
High voltage
waveform
6% duty cycle

13. Blend
• Blend = Cut + Coag
• Enhances cutting current to coagulate small bleeders while dissection
• And coagulation current to dissect during hemostasis
• Modification of the duty cycle

14. Electrosurgical tissue effects
• Coagulation
• Heating effect cell death by dehydration and protein denaturation
• Bleeding stopped by:
• Distortion of vessel wall
• Coagulation of plasma proteins
• Dried and shrunken tissue
• Stimulation of clotting factors
• Intra cellular temperature <100°Cmay produce cutting effect if it exceeds
• Temperature (60-90) °C

15. • Cutting
• Temperature 100°C or above
• Due to intense heat cell explode and vaporize
producing cutting effect
• Fulguration
• Electrosurgical fulguration (sparking with the
coagulation waveform) coagulates and chars the
tissue over a wide area.
• Uses coagulation current and higher voltage is used to
make larger sparks/arcs jump an air gap
• Continues until carbonization or charring
• Use of high voltage coagulation current has
implications during minimally invasive surgery.

16. Desiccation
• Electrosurgical desiccation occurs when the electrode is in direct contact
with the tissue
• Desiccation is achieved most efficiently with the “cutting” current
• By touching the tissue with the electrode, the current concentration is
reduced
• Less heat is generated and no cutting action occurs
• Cells dry out and form a coagulum rather than vaporize and explode.
• . The benefit of coagulating with the cutting current is that you will be
using far less voltage
• This is an important consideration during minimally invasive procedures

17. Diathermy hazards/ complications
• Electrocution
• Occurs if 50-60Hz Alternating current used
• Overcome by using diathermy devices that produces current frequency
>50kHz
• Explosion
• Sparks from diathermy equipment can ignite volatile or inflammable gas or
fluid within the OR
• Alcohol based preparation can catch fire
• Avoid in presence of explosive gases  which present naturally in colon(after
bowel preparation with mannitol)

18. • Burns:
• Most common type of diathermy accident
• causes third degree/full thickness burn
• Cause
• incorrect application of the patient plate
• Patient earthed by touching any metal object-  OT table, anesthesia bar,
etc
• Faulty insulation of the diathermy leads , either due to cracked insulation
or instruments
• Inadvertent activity: accidental activation of foot pedal or accidental
contact of active electrode with other metal instruments
• Burn= (current* time)/Area

19. Channeling effect
• Occurs if current passes up a narrow
channel or pedicle through tissue/organ
• Current intensity may produce heating
effect in narrowest part of channel/pedicle
• Coagulating the tissue
• May be hazardous in cases:
• Coagulation of penis in child during
circumcision
• Coagulation of spermatic cord when electrode
applied to testis

20. Pacemakers
• Diathermy interferes with working of pacemakers causing:
• Alteration of pacemaker function resulting in arrhythmia or cardiac arrest
• Current travelling down the pacemaker wire may cause myocardial burn causing
cardiac arrest
• Diathermy surgical smoke/plume
• Composed of 95% steam and 5% cellular debrisª
• Contains variety of toxic mutagenic chemicals like HCN , benzene
• Viruses and viable cancer cells an also be transmitted via surgical smoke and
diathermy machine( Eg, HPV
• Mutagenic potency of condensates from 1gm of tissues is equivalent to smoking 6
unfiltered cigarettes®

21. Laparoscopic surgery
• Diathermy burns most likely hazard in laparoscopic
surgery
• Relative lack of visibility of instrumentation
• Crowded working space
• Structure of instrument

22. • Burns occur by:
• Diathermy of wrong structure
• Inadvertent activation of the pedal
while the diathermy tip is out of
vision
• Retained heat in the diathermy tip
touching susceptible structure–
bowel
• Insulation failure
• Direct Coupling
• Intraperitoneal contact of the
diathermy with another metal
instrument

23. Capacitance coupling
• Occurswheneveranonconductor separatestwo conductors
• Metallaparoscopic port and insulated diathermyhook passed through it
• Current flowing through hook induces current in the metalport by Electromagnetic
inductioncurrent dissipates via abd wall(but may a damageintraperitoneal
structure)
• This effectcan be avoided using plastic port
• Avoid hybrid port (most disastrous)

24. Safety precautions
 TheESU should not be used in the presence of flammable
agents (i.e.,alcohol and/or tincture-based agents)
 Avoid oxygen-enriched environments
 Theactiveelectrode(s)should beplacedin a clean,dry,well-
insulated safety holsterwhen notin use
 Radiofrequency is not alwaysconfined by insulation
Currentleakage does occur
 It is recommended that:
 Cords not be wrapped around metal instruments
–Cords not be bundled together

25. Advanced energy devices
• Bipolar electrosurgery devices
• Vessel sealing system used in laparoscopic and open
surgery
• Fuses the vessel walls to create a permanent seal
• Used in general surgery, colorectal, urosurgery
gynecological surgery
• Uses combination of pressure and energy to create
vessel fusion which can withstand up to 3*Normal
Systolic BP

26. • Ligasure system-
• Uses body’s own collagen and elastin
to both seal and divide, allowing
surgeons to reduce instrument
handling when dissecting and grasping
• has feedback sensing technology which
automatically discontinues energy once
sealed
• Can seal vessels up to 7nm diameter
with an average seal time of 2-4
seconds
• It can dissect, seal and divide

27. Harmonic scalpel Devices
• Uses ultrasound technology to cut tissues while simultaneously sealing
them
• Uses hand-held ultrasound transducer and scalpel controlled by hand or
foot pedal
• Scalpel vibrates in 20000-50000Hz range and cuts through tissues
• Achieves hemostasis by sealing vessels and tissues by tissue
denaturation produced by vibration
• Provides cutting precision even through thickened scar, improves visibility (
coz smokeless)
• Can coagulate only when it cuts
• Takes longer time to cut and coagulate

28. • Advantages of harmonics
• Less swelling, bruising and bleeding
• Less collateral thermal damage
• Less charring and desiccation
• Reduces operative time and enhances recovery
• Uses :
• Laparoscopic surgeries
• Thyroidectomy
• Plastic surgeries
• Cosmetic breast surgery

29. Take home message
• Diathermy is an important tool in surgical practice
• Monopolar and bipolar diathermy have their own pos and cons
• Electrosurgical unit to be confirmed before initialing diathermy use
• Proper handling of the the diathermy to minimize inadvertent
complications
• Surgical smoke is toxic and mutagenic and should be evacuated
• Diathermy should be used cautiously in patients with pacemakers,
cochlear implants and

30. THANK YOU

31. References
• Bailey and love’s Short practice of surgery
• Sabistons’ text book of surgery
• Principles of electrosurgery –Covidien
• ª surgical diathermy and electrical hazards: causes and prevention, James H MacG
Palmer, Anaesthesia and intensive care medicine
• ®diathermy awareness among surgeons- An analysis in Ireland, Ann MEd Surg
,2016