Thermal conduction, compression, and electrical current--an evaluation of major parameters of electrosurgical vessel sealing in a porcine in vitro model.

Bipolar vessel sealing is pivotal in laparoscopic hemostasis. However, major coaptive desiccation parameters have yet to be investigated in detail. The current investigation aims to study the impact of compressive pressure, thermal conduction, and electrical current effects on seal quality in a randomized, controlled experimental trial in an in vitro porcine model of vessel sealing. A total of 106 porcine vessels were sealed with either bipolar current or thermal conduction. Compressive pressure on the sealing site and maximum temperature were varied and monitored. Additionally, the longitudinal vessel tension was measured. The burst pressure of the resulting seal was determined as an indicator of seal quality. In bipolar coaptation, seal quality depends on the compressive pressure applied to the coagulation site in both arteries and veins. The optimal pressure interval was around 270 mN/mm2 for arteries and 200 mN/mm2 for veins. Deviation from these optimal pressures towards low and high extremes led to significantly fewer successful seals. We also found that both maximum coaptation temperature and vessel shrinking correlated with the seal quality. This correlation was reciprocal in arteries and veins. Thermal conduction alone was less successful than sealing by bipolar current. Therefore, compressive pressure during coaptation determines the seal quality. Upper and lower pressure boundaries for safe coaptation exist for both arteries and veins. Vessel sealing by thermal conduction without electrical current effects is possible but represents a less effective method for coaptation. These findings have implications for the rational design of new electrosurgical instruments.