Tissue penetration of bipolar electrosurgical currents: Joule overheating beyond the surface layer.

BACKGROUND There is extensive evidence that electrosurgical current application increases hemorrhage when compared with "cold" dissection and hemostasis. The way that the "hot" technique is used may influence the outcome decisively. METHODS Temperature-time functions were measured in distances of 3 to 12 mm underneath the surface at which bipolar electrosurgical current was applied. Measurements were made in human cadaver, excised pig tissues, and pig animal models. RESULTS Bipolar current causes Joule heating in distances of several millimeters. A single maximum power pulse of 1 second increased the temperature in the muscle in 3 and 6 mm distance to 90° and 65°C, respectively; similar accumulated thermal effects were detected for a series of low- and medium-power pulses, too. CONCLUSION Joule heating is primarily responsible for unintended thermal damages. Severe damages can easily occur even in several millimeters distance from the forceps tips. Utmost caution is also advised at low power setting when current is applied repetitively.