Monday, 31 October 2011

Electrosurgical waveforms

Electrosurgery (diathermy) equipment converts domestic alternating current into high-frequency alternating current (of various types) which is converted to heat energy as it passes THROUGH a high-resistance medium such as the skin. Haemostasis can only be achieved satisfactorily if the area being diathermied is relatively dry. Each type of electrosurgical current produces its own wavy pattern of current flow, called the waveform.

Different electrical waveforms produce tissue desiccation/fulguration, coagulation, or cutting. Some machines are designed to produce all effects. There is however some overlap between these effects so that the desiccation waveform (dehydration) can be used, albeit not perfectly, for coagulation and cutting.

Monoterminal procedures (without a dispersive plate) produce desiccation/fulguration. Biterminal procedures produce coagulation with a dispersive plate or bipolar electrode (bipolar forceps, keeps the current flow on the surface travelling from one tine of the forceps to the other) or produce coagulation with cutting or pure cutting without appreciable coagulation effect (electrosection) with a dispersive plate. Pure cutting is useful in diagnostic biopsy avoiding the tissue damage associated with coagulation (after the biopsy is taken, haemostasis can be attained by switching to coagulation). 

In electrofulguration, the needle tip is not in contact with the skin. As the spark jumps between the skin and the needle its energy is spread over a greater area, resulting in more superficial tissue damage (superficial dehydration). Deep penetration does not occur because the charring acts as an insulating barrier.

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Main Works of Reference List (The first eight are my top favourites)

  • British National Formulary
  • British National Formulary for Children
  • Guidelines (BAD - BASHH - BHIVA - Uroweb)
  • Oxford Handbook of Genitourinary Medicine, HIV, and Sexual Health
  • Oxford Handbook of Medical Dermatology
  • Rook's Textbook of Dermatology
  • Simple Skin Surgery
  • Weedon's Skin Pathology
  • A Concise Atlas of Dermatopathology (P Mckee)
  • Andrews' Diseases of the Skin
  • Andrology (Nieschlag E FRCP, Behre M and Nieschlag S)
  • Bailey and Love's Short Practice of Surgery
  • Davidson's Essentials of Medicine
  • Davidson's Principles and Practice of Medicine
  • Fitzpatrick's Colour Atlas and Synopsis of Clinical Dermatology (Klaus Wolff FRCP and Richard Allen Johnson)
  • Fitzpatrick’s Dermatology in General Medicine
  • Ganong's Review of Medical Physiology
  • Gray's Anatomy
  • Hamilton Bailey's Demonstrations of Physical Signs in Clinical Surgery
  • Hutchison's Clinical Methods
  • Lever's Histopathology of the Skin
  • Lever's Histopathology of the Skin (Atlas and Synopsis)
  • Macleod's Clinical Examination
  • Martindale: The Complete Drug Reference
  • Oxford Handbook of Clinical Examination and Practical Skills
  • Oxford Textbook of Medicine
  • Practical Dermatopathology (R Rapini)
  • Sexually Transmitted Diseases (Holmes K et al)
  • Statistics in Clinical Practice (D Coggon FRCP)
  • Stockley's Drug Interactions
  • Treatment of Skin Disease: Comprehensive Therapeutic Strategies
  • Yen & Jaffe's Reproductive Endocrinology