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Year : 2015  |  Volume : 31  |  Issue : 3  |  Page : 266-267

Temperature spread of energy sources used for robot-assisted laparoscopic surgery


Date of Web Publication1-Jul-2015

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How to cite this article:
Choudhary GR. Temperature spread of energy sources used for robot-assisted laparoscopic surgery. Indian J Urol 2015;31:266-7

How to cite this URL:
Choudhary GR. Temperature spread of energy sources used for robot-assisted laparoscopic surgery. Indian J Urol [serial online] 2015 [cited 2022 May 18];31:266-7. Available from:

Hefermehl LJ, Largo RA, Hermanns T, Poyet C, Sulser T, Eberli D. Lateral temperature spread of monopolar, bipolar and ultrasonic instruments for robot-assisted laparoscopic surgery. BJU Int 2014;114:245-52

   Summary Top

Energy sources for tissue cauterization generate heat; when the temperature rises above 45°C, this can damage the adjacent, sensitive structures by denaturation of proteins. In the present study, the authors systematically evaluated the critical thermal spread of robotic coagulation devices in thin strips of fresh bovine muscle fascia. Considering variable power setting and duration, they describe the extent of thermal damage produced by robotic instruments.

A thin strip of fresh bovine muscle fascia measuring 60 mm × 4 mm was preserved at 4°C until use. These strips were held in place by applying constant traction of 25 g and pre-heated to 32°C, which corresponds to the peritoneal temperature measured during robot-assisted laparoscopic radical prostatectomy by a temperature probe. The strips were positioned over warm water bath with temperature set to 32°C to maintain this constant temperature. Robotic and laparoscopic instruments used were Hot Shears®, Permanent Cautery Hook®, Maryland Bipolar Forceps® and PreCise Bipolar Forceps® (Intuitive Surgery, USA). Three modern tissue-sealing devices with electric generators that employ active feedback: PK Dissecting Forceps® (Intuitive Surgery, USA), LigaSure LF 1537® (Valleylab, Covidien, USA) and the ultrasonic Harmonic ACE Curved Shears®. Power sources used were an Erbe VIO (Erbe Medical, Germany) generator for electrosurgical devices and Harmonic Generator 300 (Ethicon Endo-Surgery Inc., USA) for ultrasonic instruments Gyrus ACMI PK/SP Generator (Gyrus, Olympus, Southborough, MA, USA) for PK and Valleylab Force Triad Energy Platform (Valleylab, Covidien, USA) for LigaSure. Monopolar and bipolar instruments were investigated at different power settings (30, 60 and 90 W) and application time. The tissue-sealing devices were applied up to their termination signal. The ultrasonic instrument was operated in three power modes (1, 3, 5) for 1 s as well as at various application times (0.5, 1, 2 and 4 s) in power mode 3. For completeness, the ultrasonic instrument was also applied until termination signal (power mode 5 at 4 s). To evaluate whether an additional instrument could serve as a heat sink, the measurements at 1 s were repeated with a Maryland instrument placed laterally to the cauterization instrument.

A modified lactate dehydrogenase (LDH) assay was used to evaluate thermal damage at the protein level. Light microscopy (Leica Application Suite, Leica, Germany) was used to determine the extent of significant protein damage, assessed by measuring the distance to the blue-stained healthy tissue. Critical heat spreads of >20 mm were found with monopolar devices used for 2 s at 60 W. The thermal damage was significantly lower with bipolar energy. Safety distance of 2.1 mm was noticed with bipolar instruments used for 1 s at 60 W. At 4 s, this safety distance increased to 5 mm, while lowering the power to 30 W and 1 s reduced thermal spread to 1.5 mm. Modern vessel-sealing devices, e.g., the PK and LigaSure forceps, provided increased power output and constant impedance measurement. At the termination signal, the PK forceps showed a thermal spread of ≈3.9 mm, whereas the LigaSure and the Harmonic shears showed 3.1 mm and 2.9 mm, respectively. In this study, macroscopic findings were supported by the results at the protein level. The Maryland forceps next to the sensitive tissue significantly lowered the heat spread by a mean (range) of 0.8 (0.3-1.1) mm at the same power settings (P = 0.02). During the coagulation process, the additional Maryland forceps served as a heat sink and warmed up by 10°C. [1],[2]

   Comments Top

The authors analyze tissue damage at the cellular level by various energy sources and instruments used during robotic surgery. Sometimes, hemostatsis is crucial near vital structures and if the surgeon is unaware of the extent of thermal damage caused by these instruments, it can cause inadvertent damage. Although scientific papers regarding energy-based surgical devices are focused on coagulative potency and safety, the extent of tissue injury described by the authors seem more than that described in the past [3],[4],[5] Moreover, as the authors used a strip of tissue (kept in the best-matched physiological environment), this cannot replicate in vivo tissue and the effect of electro-cautery may be different in vivo. In vivo tissue has continuous blood supply, is connected all around to adjacent tissues , with different tissues having their own property to resist heat transmission. These factors may affect the extent of thermal damage to tissue in vivo. Goldstein et al. and Hruby et al. analyzed tissue damage with Harmonic ACE and LigaSure V and found that the damage to the adjacent tissue depends on the temperature of the blade, energy mode and application time. However, quantification of lateral tissue damage was based only on hematoxylin and eosin staining. [4] Brzeziński et al. analyzed the lateral thermal spread when using monopolar and bipolar diathermy devices as well as a bipolar vessel sealing system (Thermostapler™) by comparing a 30 and 60 W setting.[5] The infrared camera imaging showed a higher heat spread for all instruments in the 60 W compared with the 30 W setting. However, with the single and comparably long application time of 5 s, the observed differences were not statistically significant. As stated by the authors, placing a Maryland forceps adjacent to the tissue significantly sinks the heat spread; whether this sink is on the side of Maryland or all around is not clear. It will be a worthy attempt to carry out this kind of analysis in vivo, which will indicate the true extent of damage during surgery.

   References Top

Hefermehl LJ, Largo RA, Hermanns T, Poyet C, Sulser T, Eberli D. Lateral temperature spread of monopolar, bipolar and ultrasonic instruments for robot-assisted laparoscopic surgery. BJU Int 2014;114:245-52.  Back to cited text no. 1
Eberli D, Hefermehl LJ, Muller A, Sulser T, Knonagel H. Thermal spread of vessel-sealing devices evaluated in a clinically relevant in vitro model. Urol Int 2011;86:476-82.  Back to cited text no. 2
Hruby GW, Marruffo FC, Durak E, Collins SM, Pierorazio P, Humphrey PA, et al. Evaluation of surgical energy devices for vessel sealing and peripheral energy spread in a porcine model. J Urol 2007;178:2689-93.  Back to cited text no. 3
Goldstein SL, Harold KL, Lentzner A, Matthews BD, Kercher KW, Sing RF, et al. Comparison of thermal spread after ureteral ligation with the Laparo-Sonic ultrasonic shears and the Ligasure system. J Laparoendosc Adv Surg Tech A 2002;12:61-3.  Back to cited text no. 4
Brzezinski J, Ka³uzna-Markowska K, Naze M, Strózyk G, Dedecjus M. Comparison of lateral thermal spread using monopolar and bipolar diathermy, and the bipolar vessel sealing system ThermoStapler™ during thyroidectomy. Pol Przegl Chir 2011;83:355-60.  Back to cited text no. 5


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