Comparison of two different transection techniques in liver surgery—an experimental study in a porcine model

Aims

Postoperative morbidity and mortality after liver resection is closely related to the degree of intraoperative blood loss; the majority of which occurs during transection of the liver parenchyma. Many approaches and devices have therefore been developed to limit bleeding, but none has yet achieved perfect results up to now. The aim of this standardized chronic animal study was to compare the safety and efficacy of the LigaSure? Vessel Sealing System (LVSS) with the stapler technique, which is one of the modern techniques for transecting the parenchyma in liver surgery.

Methods

Sixteen pigs underwent a left liver resection (LLR). Eight pigs received a LLR by means of an Endo GIA, whereas the other eight pigs underwent liver parenchymal transection followed by simultaneous sealing by the LVSS. The operating time, transection time, blood loss during transection, and time of hemostasis were measured on the day of LLR (postoperative day 0/POD 0). Animals were re-explored on postoperative day 7 (POD 7) and the transection surface of remnant liver was observed for fluid collection (hematoma, biloma, and abscess), necrosis, and other pathologies. A biopsy was taken from the area of transection for histopathological examination.

Results

All animals survived until POD 7. Operating time and transection time of the liver parenchyma on POD 0 was significantly shorter in the stapler group. There was no significant difference between the two groups in terms of blood loss during transection, time of hemostasis and number of sutures for hemostasis on POD 0, morbidity rate, as well as the histopathological examination on POD 7. Furthermore, the material costs were significantly higher in the stapler group than in the LVSS group.

Conclusion

In this standardized chronic animal study concerning transection of the parenchyma in liver surgery, LVSS seems not only to be safe, but also comparable with the stapler technique in terms of morbidity and mortality. Additionally, LVSS significantly reduces material costs. However, the transection time is significantly longer for LVSS than for the stapler resection technique.     

Evaluation of fluid absorption during flexible ureteroscopy in an in vivo porcine model

Objective

To evaluate the relationship between renal pelvis pressure and fluid absorption during ureteroscopy (URS) in a live porcine model.

Materials and Methods

Flexible URS (fURS) was performed in anaesthetised female Yorkshire pigs. Prior to performing fURS, a 0.3556-mm (0.014″) pressure-sensing guidewire (Comet™, Boston Scientific) was placed to monitor renal pelvis pressure. A simulated fURS procedure was then performed for 1 h. Infusion of irrigation fluid (5% ethanol in saline) at target renal pelvis pressures (37–150 mmHg) was maintained for 1 h using a pressure bag and real-time feedback from the pressure-sensing guidewire. Venous blood was sampled every 10 min. The volume of irrigation fluid absorbed was estimated with established equations.

Results

A URS procedure was performed in vivo in 18 porcine kidneys and the volume of irrigation fluid absorbed during the 1 h URS was calculated. The mean (SD) volume of irrigation fluid absorbed after 1 h of simulated URS was 7.6 (5.7), 10.8 (7.1), 26.0 (15.8), and 56.8 (22.3) mL at renal pelvis pressures of 37, 55, 75, and 150 mmHg, respectively. Compared with URS with renal pelvis pressure of 37 mmHg, the volume of fluid absorption was significantly greater at renal pelvis pressures of 75 and 150 mmHg (P = 0.026 and P = 0.047, respectively). In addition, compared with URS with renal pelvis pressure of 37 mmHg, the rate of absorption was significantly greater at renal pelvis pressures of 75 and 150 mmHg (both P < 0.001).

Conclusion

In this study of an in vivo porcine model of URS, increasing renal pelvis pressures during URS were associated with increases in irrigation fluid absorption and increases in the rate of fluid absorption.     

Endoluminal laser-assisted vascular anastomosis—an in vivo study in a pig model

Microvascular surgery is time consuming and requires high expertise. Laser-assisted vascular anastomosis (LAVA) is a promising sutureless technique that has the potential to facilitate this procedure. In this study, we evaluate the handling of our soldering material and the 1-week patency rate in a porcine model. Six pigs were subjected to LAVA. For each pig, the saphenous artery on one side was transected while the contralateral side was used as control. A porous polycaprolactone scaffold soaked in 40% (w/w) bovine serum albumin solution in combination with 0.1% (w/w) indocyanine green was wrapped at the anastomosis site and at the control site. Both sides were then soldered with a diode laser coupled into a light diffuser fiber emitting radiation with a wavelength of 808 nm and a power of 2–2.2 W. Vessels were successfully soldered with a 100% immediate patency rate. The 1-week patency rate was 83% for the anastomoses versus 67% for the control side. Vessels irradiated for 80 to 90 s tended to maintain the highest patency rate. Macroscopically, there was no difference between the two sides. The patch was easy to handle provided that the environment could be kept dry. This study shows the potential and the limitations of endoluminal LAVA as a one-step procedure without the use of stay sutures. Further studies are needed to improve the soldering material, the long-term patency rate, and standardized irradiation parameters. The long-term effects of laser soldering on the vessel wall remain to be determined.     

Short-term follow-up of disc cell therapy in a porcine nucleotomy model with an albumin–hyaluronan hydrogel: in vivo and in vitro results of metabolic disc cell activity and implant distribution

Purpose

Cell therapy would be favorably performed immediately after nucleotomy, to restore intervertebral disc functionality and to slow down disc degeneration. Promising results were reported from small animal models but remaining problems, especially in larger animals, include loss of vital cells due to annular damage at the injection site and detrimental intradiscal conditions. The aim of the present study was to optimize cell-based disc therapy using a new albumin–hyaluronan hydrogel together with bone marrow-derived mesenchymal stem cells in a large porcine disc model.

Methods

Luciferase cell labeling was evaluated to follow-up stem cells metabolically up to 7 days in 3D cell cultures mimicking the harsh disc environment with low oxygen and glucose concentrations. As a pilot in vivo study, the implant was injected into porcine discs after removal of ~10 % of nucleus volume and animals were killed immediately after surgery (n = 6) and 3 days later (n = 6). 24 discs were analyzed. Implant persistence and cell activity (luciferase + WST assay) were observed simultaneously.

Results

In vitro cell culture with reduction of glucose (20, 5, 0.5, 0 mM) and oxygen (21, 5, 2 %) significantly decreased metabolic cell activity and luciferase activity after 3 days, with no recovery and a further decrease after 7 days, establishing luciferase activity as a metabolic sensor. During 3 days of 3D culture with disc-like conditions, luciferase activity decreased to 8 %. In vivo, initial implant volume shrank to 61 % at day 3 with evidence for hydrogel compression. Luciferase activity in vivo at day 3 was 2 % without referencing but 23 % after referencing to in vitro cell adaptation, and 38 % after additional consideration of detected implant volume loss.

Conclusion

In vitro analysis up to 7 days established for the first time luciferase activity as a metabolic sensor for mesenchymal stem cells used in regenerative disc therapy. Under the present protocol, short-term in vivo analysis after 3 days suggests improved implant retainment inside the disc and persistence of metabolically active cells; however, further studies will have to prove long-term in vivo outcome.     

Effectiveness of various thermal ablation techniques for the treatment of nodular thyroid disease—comparison of laser-induced thermotherapy and bipolar radiofrequency ablation

Alternative minimally invasive treatment options such as radiofrequency ablation (RFA) or laser-induced thermotherapy (LITT) are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. So far, studies have not been able to show a secure advantage for neither LITT nor RFA. The aim of this study was to compare the two ablation procedures in terms of their effectiveness. Thermal lesions were induced in porcine thyroid glands either by LITT or bipolar RFA ex vivo (n = 110 each) and in vivo (n = 10 each) using power settings between 10 and 20 W. Temperature spread during application was documented in 5- and 10-mm distance of the applicator. Postinterventional lesion diameters were measured and lesion size was calculated. Furthermore, enzyme histochemical analysis of the thyroid tissue was performed in vivo. Lesion volumes induced by LITT ranged between 0.74 ± 0.18 cm³ (10 W) and 3.80 ± 0.41 cm³ (20 W) with a maximum of 5.13 ± 0.16 cm³ at 18 W. The inducible lesion volumes by RFA were between 2.43 ± 0.68 cm³ (10 W) and 0.91 ± 0.71 cm³ (20 W) with a maximum of 2.80 ± 0.85 cm³ at 14 W. The maximum temperatures were 112.9 ± 9.2°C (LITT) and 61.6 ± 13.9°C (RFA) at a distance of 5 mm and 73.2 ± 6.7°C (LITT) and 53.5 ± 8.6°C (RFA) at a distance of 10 mm. The histochemical analysis demonstrates a complete loss of NADPH dehydrogenase activity in thermal lesions as a sign of irreversible cell damage both for LITT and RFA. This study is the first to compare the effectiveness of laser-induced thermotherapy and radiofrequency ablation of thyroid tissue. LITT as well as RFA are suitable for singular thyroid nodules and induces reproducible clinically relevant lesions in an appropriate application time. The maximum inducible lesion volumes by LITT are significantly larger than by RFA with the devices used herein.     

Laparoscopic liver resection for posterosuperior and anterolateral lesions—a comparison experience in an Asian centre

Background

Minimally invasive surgery has been one of the recent developments in liver surgery, laparoscopic liver resection (LLR) was initially performed for benign lesions at easily accessible locations. As the surgical techniques, technology and experience improved over the past decades, LLR surgery had evolved to tackle malignant lesions, major resections and even in difficult locations without compromising safety and principles of oncology. It was also shown to be beneficial in cirrhotic patients. We describe our initial experience with LLR in a population with significant proportion having cirrhosis, emphasising our approach for lesions in the posterosuperior (PS) segments of the liver (segments 1, 4a, 7, and 8).

Methods

A review of patients undergoing LLR in single institution from 2006 to 2015 was performed from a prospective surgical database. Clinicopathological, operative and perioperative parameters were analyzed to compare outcomes in patients who underwent LLR for PS vs. anterolateral lesions (AL).

Results

LLR was performed in consecutive 197 patients, with a mean age of 60 years. The indications for resection were hepatocellular carcinoma (HCC) (n=105; 53%), colorectal cancer liver metastasis (n=31; 16%), other malignancies (n=19; 10%) and benign lesions (n=42; 21%). A significant proportion had liver cirrhosis (25.9%). More females underwent surgery in the AL group and indications for surgery were similar between both groups. Major liver resection was performed more frequently for the PS group than for the AL group (P<0.001) and significantly more PS resections was performed in our latter experience (P=0.02). The mean operative time and the conversion rate were significantly greater in the PS group than in the AL group (P≤0.001 and 0.03, respectively). However, the estimated blood loss (EBL), rate of blood transfusion and mean postoperative stay were similar in the two groups (P=0.04, 0.88 and 0.92, respectively). The overall 90-day morbidity and mortality rate was 21.3% and 0.5% respectively, with no differences between the two groups. Surrogates of difficulty such as operative time, blood loss, conversion and outcomes e.g., morbidity and mortality, were similar in patients who underwent PS resections with or without cirrhosis.

Conclusions

LLR in selected patients is technically feasible and safe including cirrhotic patients with lesions in the PS segments.     

Which parameters are needed for targeting a multitined radiofrequency device—an approach to a simple algorithm

Background  The use of radiofrequency ablation (RFA) for treatment of liver malignancies is limited by the high rate of local recurrences. The aim of this experimental study was to evaluate parameters describing the reproducible target volume of a RFA procedure in order to facilitate better applicator placement. Materials and methods  RFA was performed in perfused and nonperfused pig livers. The following parameters were measured: axial and transverse diameter, front margin, coagulation center, diameter of sphere ablated (D _S), distance to center (DC), and volume. Graphic overlays were utilized to visualize variability. Parameters were evaluated for Rita XL (2 algorithms), LeVeen, and Rita Xli applicators. Results  The best prediction of a reproducibly ablated target volume can be made by the diameter of the sphere ablated and the distance of the applicator tip to center of the sphere (DC). The spheres were significantly different in diameter (D _S) depending on the applicator Rita XL 29 ± 6 mm, Rita XL^wet 35 ± 5 mm, LeVeen 35 ± 8 mm, Rita Xli 44 ± 5 mm (perfused livers, p < 0.001). Graphic overlay demonstrated differences in variability that can influence the reliability of the system. Conclusions   D _S and DC as specific values for each applicator and algorithm facilitate a placement of the applicator relative to the target volume that maximizes the chance of complete ablation.     

Androgen receptors and experimental bone loss — an in vivo and in vitro study

Testosterone is a sex hormone that exhibits many functions beyond reproduction; one such function is the regulation of bone metabolism. The role played by androgen receptors during testosterone-mediated biological processes associated with bone metabolism is largely unknown. This study aims to use a periodontal disease model in vivo in order to assess the involvement of androgen receptors on microbial-induced inflammation and alveolar bone resorption in experimental bone loss. The impact of hormone deprivation was tested through both orchiectomy and chemical blockage of androgen receptor using flutamide (FLU). Additionally, the direct effect of exogenous testosterone, and the role of the androgen receptor, on osteoclastogenesis were investigated. Thirty male adult rats (n = 10/group) were subjected to: 1-orchiectomy (OCX); 2-OCX sham surgery; or 3-OCX sham surgery plus FLU, four weeks before the induction of experimental bone loss. Ten OCX sham-operated rats were not subjected to experimental bone loss and served as healthy controls. The rats were euthanized two weeks later, so as to assess bone resorption and the production of inflammatory cytokines in the gingival tissue and serum. In order to study the in vitro impact of testosterone, osteoclasts were differentiated from RAW264.7 cells and testosterone was added at increasing concentrations. Both OCX and FLU increased bone resorption, but OCX alone was observed to increase osteoclast count. IL-1β production was increased only in the gingival tissue of OCX animals, whereas FLU-treated animals presented a decreased expression of IL-6. Testosterone reduced the osteoclast formation in a dose-dependent manner, and significantly impacted the production of TNF-α; FLU partially reversed these actions. When taken together, our results indicate that testosterone modulates experimental bone loss, and that this action is mediated, at least in part, via the androgen receptor.     

Delivery efficiency of periadventitial approach in comparison of intravascular delivery: an assessment of pharmacokinetics in porcine arteries

Objective To investigate the delivery efficacy of periadventitial delivery of ^125I-iododeoxyuridine （^125I-IUdR） in comparison of intravascular delivery to determine the optimal delivery method for inhibiting post-angioplasty restenosis. Methods In 8 pigs, one side carotid, subclavian and iliac arteries of each pig were injured by balloon angioplasty with a 20% overstretches. Then, 4 mCi of ^125I-IUdR was delivered at each targeted vessel with periadventitial method in 4 pigs （periadventitial group） and with intravascular method via a porous balloon catheter in other 4 pigs （intravascular group）. The animals survived for 5 hours and the blood radioactivity was investigated prior to and hourly after procedure until sacrifice. The targeted vessels and renal arteries （for control） were harvested for gamma-counting and histological observation. Meanwhile, the radioactivity in thyroid, liver, bladder, small bowel and each kidney also were measured to determine the biodistribution of ^125I. The activities of ^125I presented in arterial and tissue specimens were compared between the two delivery groups. The targeted arteries were histologically observed and the ratio of intima to media （I ： M ratio） was calculated. Results The target arterial walls in the periadventitial group had 3.4 times as much of ^125I radioactivity as in the intravascular group, respectively （P = 0. 038） ; the blood activity in intravascular group was significantly higher than periadventitial group immediate after procedure （P〈0.05） and intravascular delivery resulted in much higher activity in urine than periadventitial delivery （P〈0.05）. The systemic biodistributions of ^125I-IUdR in the organs were slightly higher in the intravascular group （P〉0.05）. The mean I： M ratios in both groups were 0.05 without additional injury at the vessel wall. Conclusion The periadventitial delivery offered substantial advantage over intravascular approach with high local delivery efficacy. The apparent redistribution rate is more rapid following intravascular delivery.     

Carbon fiber–reinforced PEEK versus titanium implants: an in vitro comparison of susceptibility artifacts in CT and MR imaging

Neurosurgical Review - Artifacts in computed tomography (CT) and magnetic resonance imaging (MRI) due to titanium implants in spine surgery are known to cause difficulties in follow-up imaging,...     

Vascularization of Lando® dermal scaffold in an acute full-thickness skin-defect porcine model

The Lando^® dermal scaffold is a newly developed, tissue-engineered dermal scaffold material. This study sought to observe its vascularization in an acute full-thickness skin-defect porcine model. There were eight Tibetan pigs in this research. Six 5?×?5?cm full-thickness skin-defect wounds were prepared on the dorsal area of each pig, which were divided into two groups. The experimental group wounds were covered by Lando^® dermal scaffolds, while the other received Vaseline gauzes as blank control. At day 3, 7, 14 and 21 after injury, the general condition of wounds was observed, and wound specimens were obtained for HE staining, Masson staining and the expression of CD31, α-SMA and VEGF, which were examined by immunohistochemistry. The results showed the wounds in the experimental group (Lando) were drier with a lower incidence of infection, and the granulation tissues grew better and smoother than the control group. In the experimental group, the hyperemia, edema and inflammatory reactions were milder, the fibroblasts ingrew earlier, the capillaries grew mostly parallel to the wound surface which resembled normal skin, and the collagen fibers were thicker with more regular arrangement than in the control group. The CD31?+?microvessel count, α-SMA?+?microvessel count and VEGF expression of the experimental group were significantly higher than the control group at day 7 and 14 after injury (p?® dermal scaffold showed good vascularization at day 14 post grafting in an acute full-thickness skin-defect porcine model, which may be associated with increased expression of VEGF.     

Establishment of a mechanical injury model of rat hippocampal neurons in vitro

Objective： To establish a simple, reproducible, and practical mechanical injury model of hippocampal neurons of Sprague-Dawley rats in vitro. Methods ： Hippocampal neurons isolated from 1-2-day old rats were cultured in vitro. Mild, moderate and severe mechanical injuries were delivered to the neurons by syringe needle tearing, respectively. The control neurons were treated identically with the exception of trauma. Cell damage was assessed by measuring the Propidium Iodide （PI） uptaking at different time points （0.5, 1, 6, 12 and 24 hours） after injury. The concentration of neuron specific enolase was also measured at some time points. Results ： Pathological examination showed that degeneration, degradation and necrosis occurred in the injured cultured neurons. Compared with the control group, the ratio of PI-positive cells in the injured groups increased significantly after 30 minutes of injury （P 〈 0.05）. More severe the damage was, more PI-positive neurons were detected. Compared with the control group, the concentration of neuron specific enolase in the injured culture increased significantly after 1 hour of injury （ P 〈 0.05）. Conclusions： The established model of hippocampal neuron injury in vitro can be repeated easily and can simulate the damage mechanism of traumatic brain injury, which can be used in the future research of traumatic brain injury.     

Laparoscopic blood-saving liver resection using a new radiofrequency-assisted device: preliminary report of an in vivo study with pig liver

Background

The aim of any device designed for liver resection is to allow blood saving and quick resections. This may be optimized using a minimally invasive approach. A radiofrequency-assisted device is described that combines a cooled blunt-tip electrode with a sharp blade on one side in an in vivo preliminary study using hand-assisted laparoscopy to perform partial hepatectomies.

Methods

Eight partial hepatectomies were performed on pigs with hand-assisted laparoscopy using the radiofrequency-assisted device as the only method for transection and hemostasis. The main outcome measures were transection time, blood loss, transection area, transection speed, blood loss per transection area, and tissue coagulation depth. The risk for biliary leak also was assessed using the methylene blue test.

Results

The transection time was 13 ± 7 min for a mean transected area of 34 ± 11 cm². The mean total blood loss was 26 ± 34 ml. The mean transection speed was 3 ± 1 cm²/min, and the blood loss per transection area was 1 ± 1 ml/cm². Abdominal examination showed no complications in nearby organs. One biliary leak was identified in one case using the methylene blue test. The transection surface was 34 ± 11 cm², and the mean tissue coagulation depth was 9 ± 2 mm. The inviability of the coagulated surface was assessed by adenine dinucleotide (NADH) staining.

Conclusions

The radiofrequency-assisted device has shown with a laparoscopic approach that it can perform liver resections faster and with less blood loss using a single device in a minimally invasive manner without vascular control than other commercial devices. The results show no significant differences with the same device used in an open procedure.