Partial liver resection is a treatment of choice for liver tumors; the range of parenchyma excision varies from a small part of the tissue surrounding the neoplasm up to 70% of the organ. One of the major concerns during liver resection is blood loss. Thulium lasers which are characterized by the length of emission wave corresponding to a peak absorption of water create a new possibility of cutting tissues efficiently with minimal thermal damage and concurrently providing a good hemostasis control. The aim of our study was to evaluate an impact of liver transection with thulium doped fiber laser on an intraoperative bleeding and histopathological changes during postoperative period in swine model. Ten animals were subjected to open surgery partial liver resection and an incision of liver tissue with an all-fiber, diode-pumped, and continuous-wave Tm3+-doped fiber laser emitting 37.4 W of output power at ~1.94
Partial liver resection is the standard treatment for primary and secondary liver tumors. The two most common indications for liver resection are colorectal liver metastases and hepatocellular carcinomas, and the range of liver parenchyma resection varies from limited to the tissue surrounding the tumor to up to 70% of the organ [
Soon after Maiman in 1960 discovered the first ruby-based working laser, many types of gaseous, liquid, and solid materials were found applicable in a laser technique [
The aim of our study was to evaluate an impact of liver transection with all-fiber, diode-pumped, continuous-wave Tm3+-doped fiber laser on an intraoperative bleeding and histopathological changes during postoperative period in swine model.
The experiment was approved by the Second Wroclaw Local Ethics Committee for Animal Experimentation (no. 50/2012) and performed in accordance with the standards established in the directive of the EU (2010/63/EU). 10 Polish Large White (WBP) female pigs aged 10 weeks were used in this study. The animals were obtained from a single farm (The National Research Institute of Animal Production, Experimental Station in Pawłowice, Poland) and acclimatized for 2 weeks before enrolling into one of two equal groups. In both experimental groups, the animals underwent partial hepatectomy of the right lateral lobe and incision of the liver parenchyma under general anesthesia. The excised fragments of tissue were assessed by histopathology (HP). After recovery from anesthesia, pigs were kept in the pens of a vivarium for 7 days (T1 group) or for 14 days (T2 group) and, after this period of time, were euthanized with intravenous pentobarbitone (48–96 mg/kg; Morbital®, Biowet Puławy, Poland) to obtain tissues for HP.
The thulium laser used in the experiment was a prototype all-fiber, diode-pumped, and continuous-wave Tm3+-doped fiber laser. The laser was built with the use of a mode area single-mode thulium doped fiber. The silica core fiber 25
The animals were sedated with intramuscular (i.m.) injection of medetomidine (0.1 mg/kg body weight; Domitor®, Orion Pharma, Poland) and butorphanol (0.2 mg/kg body weight; Butomidor®, Richter Pharma AG, Austria) and were inserted a venous catheters into the auricular veins. Intravenous (i.v.) propofol bolus (4 mg/ kg; Scanofol®, Scan Vet, Poland) was used to induce anesthesia in pigs, to allow their placement in the dorsal recumbent position and tracheal intubation. General anesthesia was maintained with 1.5%vol isoflurane. Analgesia was provided with an i.v. constant-rate infusion of fentanyl (50
After euthanasia, pigs were subjected to necropsy with a particular emphasis on the signs of bleeding or bile leakage from the site of resection, and the specimens from this part of the liver were collected for HP.
Specimens obtained either during surgery or necropsy were immediately fixed in 4% buffered formaldehyde for 72 h and then washed in running water for 24 h. Before embedding in paraffin (Microm EC 350-1, Thermo Scientific, USA), specimens were dehydrated successively in 75%, 96%, and 100% solutions of ethanol. Paraffin blocks with the liver samples were cut into 7
Data are expressed as mean and standard deviation of average values from measurements made in specimens obtained from n animals. Data were subjected to Student’s
All animals survived the surgical procedure without any complications. They remained in good clinical condition and had a good appetite until the end of the experiment and were euthanized after 7 or 14 days in T1 or T2 group, respectively.
Intraoperatively not any signs or minor signs of bleeding during 5 minutes after cutting the tissue with Tm:fiber laser were observed in the pigs from T1 and T2 groups. No bile leakage was observed. On the surface of the excision and incision margins a carbonization was present, which macroscopically formed a 1-2 mm deep zone in the liver lobe. After 7 days carbonization was still visible, while after 14 days only small foci of carbonization remained. No extravasated blood, clots, or any other signs suggesting delayed bleeding or bile leakage were present in T1 and T2 group. After 14 days adhesion of the liver with abdominal wall or neighboring organs at the site of cutting was visible. Tissue of the liver lobe apart from the incision line showed no macroscopic changes in any of the animals (Figure
Macroscopic evaluation of right lateral liver lobe after thulium laser surgery. (a) Incision of the liver tissue with a thulium laser (first from the left), image taken intraoperatively; (b) macroscopic changes in pig liver on day 7; carbonization is visible in the resection wound; incomplete healing of the wound after incision (the first from the right); (c) a scar formation in the liver on day 14 (T2 group) after partial resection.
During HP evaluation of specimens taken intraoperatively and 7 days after surgery the superficial and deep zones of changed tissue were distinguished, whereas in T2 group both zones merged. The width of the thermally changed area and its microscopic appearance varied with time (Table
Width of the microscopic changes in the right lateral lobe of the swine liver produced by the partial resection using a Tm:fiber laser.
Specimen | T1 and T2 intraoperatively (n=10) | T1 (n = 5) | T2 (n = 5) |
---|---|---|---|
Zone of superficial thermal damage in the liver tissue [ | | | - |
| |||
Total width of microscopic thermal changes in the liver tissue [ | | | 765.35 ± 55.94 |
T1 and T2: groups of animals undergoing euthanasia on days 7 and 14, respectively. Values are presented as mean ± SD; n: number of animals. Values marked with
Histopathological evaluation of the fragment of the liver excised with thulium laser on day 0 (HE staining). (a) Magnification ×40; (b) magnification×100.
Histopathological evaluation of the liver tissue damage on day 7 after cutting with thulium laser (magnification x40, HE staining). (a) and (b) Total depth of thermal tissue damage; (c) focal necrotic lesions; (d) clear zone of carbonization in the middle of the incision wound.
Histopathological evaluation of the liver tissue at the site of transection with thulium laser on day 14 ((a) and (b) magnification x100, HE staining).
The superficial zone of the microscopic changes in specimens collected intraoperatively was characterized by exudation and carbonization without extravasated erythrocytes. In the deeper zone of thermal damage morphologically altered lobules were present; however, hepatic cells themselves had a preserved structure and intact nuclei. This layer was clearly separated from the normal liver parenchyma (Figure
In the samples from T1 group a superficial zone with carbonized tissue and exudative phase was still present; however, the width of this layer decreased significantly (Table
In the samples taken 14 days after surgery both zones merged and formed a layer of isolated areas of laser activity filled with the granulation tissue and the residues of carbonized tissue. These areas were surrounded by granulocytes mostly neutrophils, by macrophages, lymphocytes, plasmatic cells, and mesenchymal cells. In T2 group the total width of changed tissue decreased comparing with samples taken 7 days after surgery (Figure
Liver resection remains a surgery not without complications, of which a blood loss is the most serious concern. Different methods of vascular occlusion are applied, and new techniques and devices for parenchymal transection are sought to minimize bleeding. Among others cavitron ultrasonic surgical aspirator, ultrasonic shears, and radiofrequency dissecting sealer are the devices designed to cut liver parenchyma with minimal bleeding [
In the middle 80s of XX century different types of lasers were tested for their feasibility in liver surgery. Most attention was turned to Nd:YAG lasers and CO2 lasers. Na:YAG laser was compared with ultrasonic surgical aspirator and blunt dissection in a dog model of liver resection. It was not superior to the other two techniques in particular due to a large zone of thermal damage [
Thulium doped fiber lasers are promising devices in surgery due to several favorable features. Firstly, they operate at a wavelength of approximately 1940-2000 nm, which corresponds to the length of light highly absorbed by water. Most of the soft tissues is characterized by an abundance of water, and similarly, porcine liver has been shown to have a maximum absorption coefficient at 1940 nm [
Another advantageous feature of the Tm:fiber laser is that the potent local thermal effect resulting in its ability to cut is accompanied by coagulation, thus providing hemostasis. Control of blood loss is a common problem in surgery of highly vascularized tissues as kidney, spleen, or liver. As opposed to early studies on CO2 laser in liver resection, in which an efficient cutting did not produce hemostasis [
In conclusion Th:fiber laser is efficacious in cutting with a narrow zone of thermal injury and provides good hemostasis during partial liver resection and liver tissue incision. Tm:fiber laser operating at 1940 nm may be a potential tool in oncologic liver surgery, especially when sparing of a healthy tissue is being a priority and small atypical excisions are performed.
The data used to support the findings of this study are included within the article.
The authors declare that there are no conflicts of interest regarding the publication of this article.
This work was financed by the National Centre for Research and Development (Grant no. INNOTECH-K3/IN3/55/225968/NCBR) and by the Wroclaw Center for Biotechnology Program KNOW (National Scientific Leadership Center) for the 2014–2018.