Often “electrocautery” is used to describe electrosurgery. This is incorrect. Electrocautery refers to direct current (electrons flowing in one direction) whereas electrosurgery uses alternating current. During electrocautery, current does not enter the patient’s body. Only the heated wire comes in contact with tissue. In electrosurgery, the patient is included in the circuit and current enters the patient’s body.

Principles of electricity

Principles of electricity are relevant in the operating room. The electrosurgical generator is the source of the electron flow and voltage. The circuit is composed of the generator, active electrode, patient, and patient return electrode. Pathways to ground are numerous but may include the OR table, stirrups, staff members, and equipment. The patient’s tissue provides the impedance, producing heat as the electrons overcome the impedance.

*The circuit for the alternating current is depicted by arrows in opposite directions.

Standard electrical current alternates at a frequency of 60 cycles per second (Hz). Electrosurgical systems could function at this frequency, but because current would be transmitted through body tissue at 60 cycles, excessive neuromuscular stimulation and perhaps electrocution would result.

Because 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. At this frequency electrosurgical energy can pass through the patient with minimal neuromuscular stimulation and no risk of electrocution.