Overall, EEG is very safe for both the technologist and patient. However, there are known risks associated with the procedure. Exposure to electrical current is the most important determinant of injury risk and can cause injuries ranging from skin burns to induction of seizures or ventricular fibrillation. According to Ebersole and Pedley's definitive text, there are multiple potential sources that can allow harmful currents to flow through patients connected to EEG equipment, including currents from improper grounding, leakage, and double-grounding (37). Electrical grounding is very important in preventing leakage of current through the patient in case of aberrant current flow through the EEG equipment. Grounding is dependent on both the fuses within the EEG machine and the use of proper outlets to ground the machine within the room. Leakage currents can be from either stray capacitance or stray inductance and are most dangerous when combined with improper grounding. Double-grounding presents electrical risk to the EEG patient because of the existence of differences in potential between the grounds. These differences in electrical potential create gradients for current flow through the double-grounded patient. Double-grounding is most likely to occur in medical settings where patients are attached to multiple (grounded) devices.
Tips to maintain electrical safety and avoid exposure of patients to current include the following:
Establish regular EEG equipment maintenance, including protection with proper fuses.
Always use a grounding electrode, except in situations (e.g., intensive care unit, operating room) in which other electrical equipment is attached to the patient (double-grounding must be avoided.
Always connect ground electrodes to the appropriate jack of the input jack box (never to the equipment chassis or another earth ground.
Always use a three-prong plug. Hospital-grade power outlets should be used whenever possible. Do not use a three-prong to two-prong converter, as the converter does not provide the same protection as an actual grounded plug.
Do not use extension cords for EEG machines.
