Diathermy refers to the use of electrically induced heat to cut, destroy, or coagulate tissue. Though more commonly utilized in physical and occupational therapy to treat injuries and relax muscles, the approach can be used in urologic surgery. The heat generated by diathermy can destroy tumors and infected tissues along the urinary tract or male reproductive system, and can cauterize blood vessels to inhibit excessive bleeding.
How Diathermy Works
Electric currents are generated by the movement of electrons. Normally, a high-frequency alternating current is produced by a diathermy machine by entering an electrical current into it. Alternating currents (between 300 kHz to 5 MHz) cause them to randomly change direction, much like the electricity found in a wall outlet. Since the frequency is so high and rapid, muscles and tissues are not harmed as the current passes through the body.
There are three effects that electrosurgery has on body tissue:
- Coagulation: causing the blood to clot, which reduces bleeding
- Fulguration: cell walls are dehydrated and, as a result, destroyed
- Cutting: heat generation cuts through and destroys tissue cells
All of these effects can be used when:
- Removing tissue for examination (biopsy)
- Treating urological obstructions (such as urethral strictures)
- Cutting away tumors
Monopolar Versus Bipolar Diathermy
Diathermy requires an electrosurgical generator and a handpeice or radiofrequency knife. The two types of electrosurgery include:
Monopolar
Electrical currents pass through two electrodes on the patient's body—one sends a heat source to and near the tissue being targeted, while another catches the energy and sends it back to the diathermy machine. Monopolar diathermy can be used for many of the same procedures as bipolar; however, bipolar tends to be more precise with the amount of tissue affected.
Bipolar
The tissue that is being targeted is put between forcep tips. Electric energy runs along one prong through the tissue and is then reverted back to the diathermy machine through the second prong. Here, both the active and return electrodes are within one forcep. Bipolar diathermy can be much more precise for smaller amounts of tissue. For example, if a small blood vessel needed to be coagulated, bipolar would be preferred. It is also useful on patients with a cardiac pacemaker, as bipolar electric currents avoid interference with pacemakers.
Risks Associated with Diathermy
A surgical procedure utilizing diathermy can generate smoke. This smoke may be harmful since it can contain chemical by-products, carbonized tissue, blood particles, viral DNA particles, infectious viruses, or bacteria. These can be absorbed by the lungs or skin, which may cause damage if masks are not worn and proper smoke filtration systems are not used.
Those with pacemakers should consult with their doctor because diathermy currents can simulate the radiofrequency impulse of pacemakers, thereby reprogramming it or damaging it. Patients who are pregnant or who have metal inside their body or an intrauterine device should also avoid diathermy, as the heat can cause internal disruptions or damage. Health care providers should avoid the use of alcohol based cleaning solutions before the surgical procedure. Metal buttons, jewelry, or piercings should be removed by the patient.
Diathermy burns can occur if proper precautions are not taken. If the diathermy pad is not making complete contact with the patient, the electrical current searches for a way to contact earth and if it is touched, it can be dangerously hot.
Additionally, diathermy can boost blood flow to the targeted tissue; therefore, patients with hemophilia run the risk of hemorrhaging.
References
Reynard J, Turner K, Mark S, et al. (2008). Urological Surgery: Oxford Specialist Handbooks in Surgery. Oxford University Press: New York; 63:65.
Meyer J, & Crew J. (2008). The risks of diathermy in the urological patient with a pacemaker or an automatic internal cardiac defibrillator. British Journal of Urology International;101(5):528-529.
Massarweh NN, Cosgriff N, & Slakey DP. (2006). Electrosurgery: history, principles, and current and future uses. Journal Am Coll Surg; 202:520.
