New semi-spherical radiofrequency energy device for liver resection: an experimental study in pigs

The aim of this experimental study was to verify a new semi-spherical surgical tool for bipolar radiofrequency liver ablation, which can solve some of the disadvantages of the commonly used device, such as long duration of ablation. A total of 12 pigs which were randomly divided into two groups were used. Each pig underwent resection of the two liver lobes. In group 1, pigs were treated with the commonly used device; in group 2 the newly developed semispherical device was used. During surgery and the post-surgical period, many categories were observed and later analyzed. The blood count and biochemistry were monitored on days 0, 14 and 30 from the operation. On day 14 since the liver resection, pigs underwent diagnostic laparoscopy to evaluate their condition focusing on the site of the liver lobe resection. On day 30 after operation, all pigs were euthanized and subjected to histopathological examination. Histopathological evaluation of thermal changes at the resection margin showed strong thermal alteration in both groups. Data between both groups were compared using median test for continuous variables and Fisher’s exact test for categorical variables. Statistical analyses were performed with IBM SPSS software version 18.0. Statistical analysis of collected data did not prove any significant (P < 0.05) differences between the commonly used device and the newly designed surgical tool. Animal study, pig model, liver ablation, radiofrequency energy The liver is very frequently affected with metastases of colorectal carcinoma (Jemal et al. 2008). The incidence of colorectal carcinoma is increasing all around the world, including the Czech Republic (Ferlay et al. 2010; Pavlík et al. 2012). Therefore, it is necessary to focus research on the demands for instrumental equipment in liver surgery and the need to develop innovative designs (Vavra et al. 2014). This in vivo study follows an ex vivo study, which was done during the years 2009–2011. The pig as an animal model was chosen because of its availability, economic considerations, and relatively undemanding farming conditions (Varadarajulu et al. 2009; Lesser et al. 2011). Another medically justifiable ACTA VET. BRNO 2015, 84: 397-401; doi:10.2754/avb201584040397 Address for correspondence: Ass. Prof. Petr Vávra, M.D., Ph.D. Department of Surgery, University Hospital in Ostrava 17. listopadu 1790, Ostrava 708 52 Czech Republic Phone: +420 737 550 050 E-mail: [email protected] http://actavet.vfu.cz/ reason for the selection of this species was that the pig liver is similar in physiological functions, size and topographic links to other abdominal organs of the human body. Several studies have been performed using an ex vivo and/or in vivo animal model to verify the effectiveness of radiofrequency on various tissue types (Johnson and Cadeddu 2003; Date et al. 2005). The primary hypothesis was to demonstrate the feasibility and safety of the newly developed semi-spherical bipolar device for liver ablation and resection (RONJA) compared with the commonly used device for liver resection. The secondary hypothesis was to confirm that the system configuration of electrode needles into a semi-spherical shape was designed in such a way that it would shorten the ablation and thus the operation time while maintaining the same effect of thermal coagulation (Vavra et al. 2014). Materials and Methods This experimental in vivo study (no. 65/2012) was approved by the Institutional Animal Care and Use Committee of the University of Veterinary and Pharmaceutical Sciences Brno in accordance with Article 18, paragraph 6 b, of Act No. 246/1992 on the protection of animals against cruelty. Our experiment was also approved by the Ministry of Education, Youth and Sports of the Czech Republic and was granted permission to be carried out on September 7, 2012. One-year-old pigs were provided by the Research Institute of Animal Production (Uhrineves, Department of Pig Breeding, Kostelec, address: Komenskeho 1240, 517 41, Czech Republic, accreditation number 444/2011MZE-17214, valid until April 6, 2016). The whole experiment took place in the research surgical theatre of the Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic. Twelve pigs (Sus scrofa domestica) were randomly divided into two groups of six pigs. Pigs in group A underwent liver resection using the newly tested device and in control group B pigs were operated on with the commonly used surgical multiple needles device for radiofrequency liver ablation. The surgical procedure All animals were intramuscularly premedicated with a mixture of TKX – tiletamin-zolazepam (Zoletil, Virbac, France), ketamine (Narketan, Vetoquinol, Czech Republic), xylazine (Rometar, Bioveta, Czech Republic) (2 mg/kg from each subs.) and atropine (Atropin, Leciva, Czech Republic) (0.02 mg/kg). Anaesthesia was induced by intravenous propofol (Norofol, Norbrook Lab. Ltd., North Ireland) (0.5–1 mg/kg), then anaesthesia was maintained by a constant rate infusion of propofol (0.1 mg/kg/min). The surgical field and surroundings were shaved and made antiseptic by washing with iodopovidon (Betadine soap, Egis Pharmaceutical, Hungary); chlorhexidine (Nolvasan, Cymedica s.r.o., Czech Republic) was applied to the surgical field. During the surgical procedure Hartmann solution (B. Braun, Germany) 10 ml/kg/h were administered to the animals intravenously through a cannulated auricular vein. Postoperatively, the animals were administered amoxicillin (15 mg/kg) and meloxicam (0.4 mg/kg) (Metacam, Boehringer Ingelheim, Germany) intramuscularly. An upper middle laparotomy was performed with the position of the animal on its back. Two liver resections were always performed on each pig (Plate VI, Fig. 1) one from the right lateral lobe and one resection of the left lateral lobe of the liver (Plate VI, Fig. 2). The resected samples were fixed in 10% formalin solution for a follow-up histopathological examination. The entire abdominal laparotomy was closed in three layers (peritoneum together with fascia, subcutaneous tissue, skin). A special antiseptic spray Silver Aluminium Aerosol (Henry Schein, Inc., Germany) bandage protection against contamination was applied to the surgical wound (Vavra et al. 2014).