Lateral temperature spread of monopolar, bipolar and ultrasonic instruments for robot-assisted laparoscopic surgery




  • To assess critical heat spread of cautery instruments used in robot-assisted laparoscopic (RAL) surgery.

Materials and Methods

  • Thermal spread along bovine musculofascial tissues was examined by infrared camera, histology and enzyme assay.
  • Currently used monopolar, bipolar and ultrasonic laparoscopic instruments were investigated at various power settings and application times.
  • The efficacy of using an additional Maryland clamp as a heat sink was evaluated.
  • A temperature of 45 °C was considered the threshold temperature for possible nerve damage.


  • Monopolar instruments exhibited a mean (sem) critical thermal spread of 3.5 (2.3) mm when applied at 60 W for 1 s. After 2 s, the spread was >20 mm.
  • For adjustable bipolar instruments the mean (sem) critical thermal spread was 2.2 (0.6) mm at 60 W and 1 s, and 3.6 (1.3) mm at 2 s.
  • The PK and LigaSure forceps had mean (sem) critical thermal spreads of 3.9 (0.8) and 2.8 (0.6) mm respectively, whereas the ultrasonic instrument reached 2.9 (0.8) mm.
  • Application of an additional Maryland clamp as a heat sink, significantly reduced the thermal spread.
  • Histomorphometric analyses and enzyme assay supported these findings.


  • All coagulation devices used in RAL surgery have distinct thermal spreads depending on power setting and application time.
  • Cautery may be of concern due to lateral temperature spread, causing potential damage to sensitive structures including nerves.
  • Our results provide surgeons with a resource for educated decision-making when using coagulation devices during robotic procedures.