Energy is used every day in the majority of surgical procedures. where  cutting, vaporization, or hemostasis is required.  Energy-based hemostasis is achieved by sealing vessels (electrocoagulation or electrodesiccation) or, for capillary like bleeding, by the process of fulguration. But it is also true that a large proportion  of surgical complications are related to energy; almost all preventable with adequate understanding and the conscious use of a number of principles and techniques. Consequently, it is incumbent on all trainees and surgeons to be intimately familiar with the energy systems that they use. 

By far the most common form of energy used for surgery is radiofrequency (RF) electricity, applied via a spectrum of instruments that can be used laparotomically, vaginally, hysteroscopically or laparoscopically. Another commonly used form of energy is ultrasound that is most often deployed in laparoscopic instruments. The videos and other material here are designed to, in a compressed fashion, provide you with the fundamentals of these energy sources - but a more extensive training program for energy (with the exception of that used at hysteroscopy) can be found in the "FUSE" program, an on-line training system that is available free of charge, and produced by SAGES, the organization that brought you FLS. You just have to provide your specialty and name to create log-in credentials. We should suggest that you especially review Modules 1-5 and 10 of the FUSE program. You can get to it by clicking the FUSE logo at the top of the page.

• All electrical circuits require two poles that possess different electrical potentials; as a result electrons flow between the two poles.
  
• In a "direct current" (DC) circuit, the polarity doesn't change, so electrons flow in only one direction. 
  
• Alternating currents (AC) might better be called "Alternating Polarity" current since the polarity in the circuit changes with each half cycle. This design results in no net movement of electrons and other ionized atoms and molecules.
  
• For RF electricity, the polarity typically changes approximately 500,000 times per second or 500 kilohertz (kHz)  
• While ALL RF electrosurgery is bipolar, monopolar instruments possess only one of the electrodes, while bipolar devices are constructed to include both electrodes.
• Radiofrequency (RF) electrical energy creates tissue effects by inciting rapid oscillation of intracellular ions, including proteins, in concert with the alternating polarity of the circuit. This, tumultuous intracellular event results in an elevation of intracellular temperature .
•  If the intracellular tissue rapidly reaches 100ºC, the intracellular water boils and the cell ruptures in a process called vaporization.
• When the intracellular temperature rapidly exceeds 60ºC, but does not reach 100ºC, the cells undergo desiccation (they lose intracellular water) and coagulation (protein denaturation and reformation). If this process is sustained, the tissue temperature increases by the process of resistive heating similar to what occurs in an incandescent light bulb.
  
• The most important method by which the surgeon controls the tissue effect is by focusing, or defocusing the current; high current concentration (high current or power density) more likely results in rapid elevation of cellular temperature and vaporization, while lower current density results in desiccation and coagulation.
  
• The most efficient waveform (the output of the Electrosurgical Unit or ESU) for RF electrosurgical cutting is the relatively low voltage “cut” waveform.
  
• Paradoxically, the same waveform should ALWAYS be used for tissue coagulation.
  
• Fulguration is a unique type of superficial coagulation that is accomplished using the modulated high voltage output called “coagulation”, usually applied with a relatively large surface area electrode (eg a ball electrode) held close to, but not in contact with tissue, allowing the current to arc to the target site.
• The principles of RF electrosurgery also apply to intrauterine techniques but all are performed in a fluid environment. Monopolar intrauterine RF instrumentation requires the use of media without electrolytes while bipolar instruments demand that electrolyte rich solutions be used. 
• Ultrasonic devices do not require an electrical circuit to create an effect instead, relying upon the process of rapid linear oscillation of a blade (about 55 kHz)  to both mechanically transect and vaporize tissue, while, at the same time create a variable amount of tissue coagulation.

Energy's 6 Modules

In this module you will be introduced to a number of fundamental concepts regarding electricity and radiofrequency (RF) electricity. This is foundational to your understanding of how the devices work, and, ultimately, how you can use them safely. You will also learn why RF electrosurgery is NOT "cautery" , that RF electricity does NOT flow in and direction and be introduced to a number of electrosurgical terms that may be different from what you have heard elsewhere but which should clear up confusion and help you understand the function of new devices as they are presented to you. This module will also describe the function of the electrosurgical generator (NOT the "Movie"!), the difference between bipolar and monopolar instruments and hopefully will help you understand that (essentially) all RF electrosurgery is bipolar, the differences are the location and purpose of the second electrode. 

In this module you will learn how RF electricity causes a tissue effect, starting with the impact that it has on living cells which is basically achieved by increasing the intracellular temperature, initially by the process of intracellular oscillation of proteins and other ionic substances. How quickly this is done has a lot to do with the result - rapid elevation to 100ºC results in vaporization, slower elevation to a lower temperature (60-95º) results in cellular dehydration ("desiccation") and protein coagulation. You will then learn that performing RF electrosurgery, and changing the cellular/tissue effect has more to do with focusing the energy, than on any specific features of the waveforms - although there are important differences. Finally we hope that you learn that the best tissue coagulation effect is achieved by the low voltage output called "cut" in many generators - who would have known?

Since so much bipolar laparoscopic instrumentation is now used for hemostasis, we thought that it would be important to include a separate module on bipolar instrumentation. You will be reminded that bipolar RF instruments still use the same energy - they just have two electrodes in the device rather than one which is the case for monopolar instruments such as the hand held electrosurgical blade that you might use in laparotomy surgery (for example when performing a Cesarean delivery. There are "generic" bipolar instruments that use low voltage ("cutting") current by default, but tend not to have special tissue monitoring systems and there are proprietary bipolar instruments that have their own electrosurgical generator and which use sensors and software to provide feedback regarding when the tissue has been appropriately coagulated. 

This module deals with the potential risks and complications associated with the use of RF electrical energy for surgery. You will understand the role of direct and capacitative coupling in this process as well as the safe storage of these devices when not in use. We hope that you will learn even more about the higher risks of high voltage ("coagulation") waveforms, which are inferior for vessel sealing (yes, for coagulation - who would have known?), and present higher risks for current diversion when used with monopolar instruments. You will also learn how to identify high risk situations such as those created when tissue coagulation induced impedance causes current to be diverted to places that you don't want it to go.

The use of RF energy at hysteroscopy isn't new, and, in many instances is being supplanted by other electromechanical instruments. However, it is still an important component of the armamentarium of the minimally invasive surgeon, and it is NOT covered in the FUSE program discussed at the beginning of this section. Here you will learn the unique aspects of RF electricity in the uterus and the profound differences between monopolar and bipolar instrumentation both with respect to the design of the system and the need for very different distention media. The types of complications unique to intrauterine surgery and with monopolar and bipolar devices are also covered.