The Distribution of Radiofrequency Current and Burns

During electrosurgery, nine patients were burned at the sites of electrocardioscope electrodes. Causes were: 1) broken patient-plate ground wires detectable only by conductivity measurements; 2) defective silicon-controlled rectifiers in the sentry modules; 3) a design fault apparent only when the foot switch of one company was used with the electrosurgery machine of another; 4) improper use of the active (knife) electrode; 5) capacitive coupling of radiofrequency current in electrocardioscope cables; and 6) radiofrequency current division. The average maximum radiofrequency current in the ground electrode of an electrocardioscope system was 175 milliam-neres (range 20–290). Approximately 100 milliamperes/cm2 for approximately 10 sec can cause skin damage. Current through an ECG ground electrode during a median sternotomy was ten times greater when this electrode was placed on the upper arm rather than the calf–in each case the ground plate was under the butttock. Radiofrequency inductors (chokes) may prevent these burns.