Spread of thermal energy and heat sinks: Implications for nerve-sparing robotic prostatectomy

Background and Purpose: During nerve- sparing robot- assisted laparoscopic prostatectomy, nerve injury caused by thermal energy is a concern. Using a porcine model, we studied thermal spread and queried whether vessels such as the prostatic pedicle may act as a heat sink, reducing the spread of thermal energy. Materials and Methods: Monopolar (MP) and bipolar (BP) cautery was applied laparoscopically on the anterior abdominal wall surface of six pigs with the da Vinci robot. Using fiberoptic thermometry (Luxtron Inc. Santa Clara, CA), temperatures were recorded with and without the interposed inferior epigastric vessels to evaluate the heat sink effect. Results: Interposition of the inferior epigastric vessels definitively demonstrated a heat sink phenomenon: at 7 mm from the MP/ BP energy source, temperatures rose 10.7 degrees C to 13.8 degrees C without interposed vessels versus only 1.9 degrees C to 2.5 degrees C when vessels were interposed (P < 0.001). Conclusion: The heat sink phenomenon suggests that the prostatic vascular pedicle should be protective of the neurovascular bundle during transection of the bladder neck during laparoscopic prostatectomy.