Real time monitoring of temperature changes in neurovascular bundles during robotic radical prostatectomy: thermal map for nerve-sparing radical prostatectomy.

OBJECTIVE: A rise in temperature of more than 55 degrees C in tissues, even for short a duration has been implicated in irreversible tissue damage. This study was aimed at recording real time temperature changes at the neurovascular bundle (NVB) during the use of cautery in robotic radical prostatectomy. METHODS: The temperature was monitored with a needle electrode in 15 cases of athermal nerve sparing and 10 cases of non-nerve sparing robotic radical prostatectomy (RRP). The needle was placed in the peritoneal cavity through the camera port and inserted around the NVB. Body temperature was recorded by nasal cannula and compared with the baseline temperature at the neurovascular bundle. The distance of the needle probe from the area of cautery use, changes in temperature at the neurovascular bundle and the duration of cautery use was recorded during the use of monopolar and bipolar current in tissue dissections. RESULTS: The mean baseline temperature at the neurovascular bundle was 0.8 degrees C lower than the body temperature. Average duration for cautery use at the anterior bladder neck and NVB with monopolar and bipolar current was 53.6 (45-65) and 79.8 (70-92) and 56.8 (45-60) and 65.7 seconds (59-76) respectively. The mean temperature rise during bladder neck dissection (distance more than 1 cm) was 43.6 degrees C [36.4-47.3 degrees C] with the monopolar and 38.8 degrees C [36.8 degrees-42.6 degrees C] with bipolar. During NVB dissection, the mean temperature rise was 53.6 degrees C (45.1 to 68.1 degrees C) with monopolar and 60.91 degrees C (47.2 to 109.8 degrees C) with bipolar. Though this difference was not significant, the mean time to return to baseline temperature was 3 seconds more with bipolar than monopolar. CONCLUSIONS: Bipolar cautery may not be safer than monopolar because of a greater rise in temperature of surrounding tissues within 1 cm of its use. Further investigation is needed to fully establish the pathologic consequences associated with increased temperature due to cautery.