Diathermy principles and types

Presentations

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)= I 2 (current density)* R(resistance)* t(time)

5. Electrosurgery Electrocautery Uses Alternating Current Uses Direct Current ( electrons flo w in only one direction) the patient is included in the circuit and current enters the patient’s body. current does not enter the patient’s body Only the heated wire comes in 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. F requency Spectrum Standard electrical current alternates at a frequency of 60 cycles per second (Hz) current transmitted through body tissue at 60 cycles causes excessive neuromuscular stimulation and perhaps electrocution nerve and muscle stimulation cease at 100,000 cycles/ second (100 kHz) electrosurgery can be performed safely at “radio” frequencies above 100 kHz An electrosurgical generator takes 60 cycle current and increases the frequency to over 200,000 cycles per second surgical diathermy uses frequency in range of 400kHz -10MHz

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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.

15. 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 C ells 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

16. 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 )

17. 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

18. 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

19. 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®

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

21. 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

22. Capacitance coupling O ccurs whenever a nonconductor separates two conductors Metal laparoscopic port and insulated diathermy hook passed through it Current flowing through hook induces current in the metal port by Electromagnetic induction current dissipates via abd wall (but may a damage intraperitoneal structure) This effect can be avoided using plastic port Avoid hybrid port (most disastrous)

23. Safety precautions The ESU should not be used in the presence of flammable agents (i.e., alcohol and/or tincture-based agents) Avoid oxygen-enriched environments The active electrode(s) should be placed in a clean, dry, well- insulated safety holster when not in use Radiofrequency is not always confined by insulation Current leakage does occur It is recommended that: Cords not be wrapped around metal instruments Cords not be bundled together

24. 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

25. 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

26. 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

27. 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

28. 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

29. THANK YOU

30. 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