Real-time thermography during energized vessel sealing and dissection

Background: Energized dissection systems facilitate laparoscopic dissection and hemostasis and reduce instrument traffic. However, they can introduce undesirable thermal collateral/proximity damage to adjacent structures mainly by heat conduction, although other mechanisms may be involved. The latest generation devices have the potential to reduce the incidence of such problems through use of active feedback control over the power output. This effectively regulates the delivery of energy to the target tissue with minimal thermal collateral damage. In addition, innovative heat-sink engineering of the device head ensures that the surface of the instrument tip remains cool (<45°C). In this study, we evaluated the performance of this technology (LigaSure) by using dynamic infrared thermography. The thermal imaging measurements were then correlated with histopathologic studies. The overall value of in situ thermography as an adjunct to energized surgical dissection systems was also assessed. Methods: Eight anesthetized pigs underwent open surgery to mobilize eight target vessels/organs in a randomized fashion. The LigaSure vessel sealing system with Instant Response Technology was used with three different interchangeable heads. In situ dynamic thermography was undertaken with a thermal imaging camera operating in the mid-infrared (3-5 μm) waveband and with each fully digitized 12-bit thermographic frame acquired at a rate of 60 Hz. Following sacrifice at the end of the dissection, tissue from the dissected regions was harvested for histology by an independent pathologist who was blinded to the thermographic data. Results: Seals made with both the LS1000 5-mm laparoscopic head (predominantly to the small bowel and colon) and the LS1100 10-mm (Atlas) device (on the liver and short gastric tissues) were outwardly satisfactory. The average thermal spread (<(Theta)over bar>) with the LS1000 was (Θ) over bar = 4.4 mm, and the exposed surface of the instrument tip developed a temperature of approximately 100degreesC. This instrument thus has the potential, albeit small, for heat-related proximity iatrogenic injury. The more technologically advanced LS1100 10-mm laparoscopic instrument exhibited a superior performance, with (Θ) over bar = 1.8 mm, and with a maximal temperature on the exposed surface of the jaws well within tolerable limits (approximately 35degreesC) for use during surgery (laparoscopic or open). This was confirmed by histological studies that demonstrated negligible evidence of thermal damage. Conclusions: In situ thermal imaging represents a powerful modality for the monitoring of energized dissection/coagulation during surgery. The LigaSure system used with the LS1100 head constitutes a very safe option for energized dissection and hemostasis of vessels with a diameter of up to approximately 7 mm.