Zhe Feng, Shan-Pei Wang a , Hao-Hua Wang b , Qiang Lu c , Wei Qiao d , Kai-Ling Wang ,Hong-Fan Ding , Yue Wang , Rong-Feng Wang , Ai-Hua Shi b , Bing-Yi Ren e ,Yu-Nan Jiang e , Bin He e , Jia-Wei Yu e , Rong-Qian Wu b , Yi Lv , ?

a Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China

b National Local Joint Engineering Research Center for Precision Surgery & Regenerative Medicine, Shaanxi Provincial Center for Regenerative Medicine and Surgical Engineering, Institute of Advanced Surgical Technology and Engineering, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China

c Department of Geriatric Surgery, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an 710061, China

d Department of Hepatobiliary Surgery, Shaanxi Provincial People’s Hospital, Xi’an 710 0 0 0, China

e Zonglian College, Xi’an Jiaotong University, Xi’an 710 0 0 0, China

Keywords:Liver transplantation Laparoscopy Magnetic surgery Vascular anastomosis

ABSTRACT Background: Although laparoscopic technology has achieved rapid development in the surgical field, it has not been applied to liver transplantation, primarily because of difficulties associated with laparoscopic vascular anastomosis.In this study, we introduced a new magnetic-assisted vascular anastomosis technique and explored its application in laparoscopic liver transplantation in pigs.

Introduction

Liver transplantation is the most effective treatment modality for end-stage liver diseases [1].The operation can be adequately performed through a “J-shaped incision”or “classic Mercedes incision”[2].However, there are certain drawbacks, such as complexity of the operation, large incision and long operative time [3].Moreover, the high rate of incision-related complications after liver transplantation results in a long hospital stay, high cost, and decreased quality of postoperative life [4–6].Furthermore, surgical site infections caused by multidrug-resistant bacteria are associated with increased morbidity and mortality [3].In addition, there is no evidence for any conservative intervention that offers significant benefits in reducing wound complications in liver transplantation [7].

Fig.1.Magnetic vascular anastomosis ring (MVAR).A: Gap elliptical MVAR for recipient SHVC; B: integrated elliptical MVAR for recipient SHVC; C: MVAR for recipient PV and IHVC; D: MVAR for donor liver PV and IHVC.SHVC: suprahepatic vena cava; PV: portal vein; IHVC: infrahepatic vena cava.

Laparoscopic surgery has shown a rapid development in the last 30 years [8].It is nowa routine practice in many institutions because of its well-known benefits of reduced intraoperative bleeding, postoperative analgesic consumption, fewer postoperative morbidities, and enhanced recovery [ 9 , 10 ].Till date, left lateral sectionectomy, laparoscopic left hemihepatectomy, laparoscopic major hepatectomy, and laparoscopic kidney transplantation have been successfully used in many cases [11–14].Currently, no laparoscopic liver transplantation is routinely performed in transplant centers in the world.And no research team has performed it on animal experiment.Although Dokmak et al.reported the world’s first “l(fā)aparoscopic liver transplantation”, he only performed laparoscopic hepatectomy on the recipient and carried out piggyback liver transplantation [15].No clinical or animal studies have been conducted on laparoscopic orthotopic liver transplantation (LOLT) and major vascular reconstruction in laparoscopic liver transplantation.In our previous study, it has been confirmed that magnetic-assisted vascular anastomosis has a shorter reconstruction time and less complications [16–18].In this study, we aimed to verify the feasibility of laparoscopic liver transplantation using a new magnetic vascular anastomosis ring (MVAR).

Methods

MVA devices

In this study, we used two sets of MVARs.One set was used for anastomosis of the suprahepatic vena cava (SHVC), and the other was used for the infrahepatic vena cava (IHVC) and portal vein (PV).To match the different diameters of the vasculature, the MVARs were designed with different diameters.The MVAR system for SHVC consisted of two elliptical magnetic rings, one integrated elliptical magnetic ring, which is used for donor liver SHVC( Fig.1 A), called DSMVAR, and a gap-elliptical magnetic ring, which is used for the recipient ( Fig.1 B), called RSMVAR.The MVAR had inner diameter of 28-36 mm and external diameter of 32-40 mm,with thickness of 2 mm and height of 4 mm.The magnetizing direction of the magnetic ring was radial, and the magnetic flux density was approximately 380 mT.

The same type of MVA system was used for the IHVC and PV systems.It consisted of NdFeB composite rings called DMVAR for the donor liver ( Fig.1 C), and a soft magnetic (No.45 steel) ring called RMVAR for the recipient ( Fig.1 D).To match the different diameters of the IHVC and PV, we also designed different RMVARs with inner diameters ranging from 10 to 22 mm, external diameter from 15 to 27 mm, thickness of 2.5 mm, and height of 3 mm.At the top of the ring, approximately every 2 mm, a perforated hole was made to place the needle, and then the needle was welded to the hole using a laser.The external diameter of the DMVAR ranged from 15 to 27 mm, the thicknesses of the top and bottom were 2.5 and 1 mm, respectively, and the height was 4 mm.The internal face of the DMVAR was a slope that accommodated the needle and expanded the anastomosis of blood vessels to avoid stenosis.The magnetizing direction of the magnetic ring was radial, and the magnetic flux density of the bottom and top was approximately 360 mT.All MVAR devices were sterilized with ethylene oxide before surgery.

Animals

Liver transplantation was performed in 12 pigs (6 females and 6 males; 3-4 months old, 35-50 kg).Loading and anastomosis of IHVC and PV was done totally with laparoscopy (case 1-3) and with hand assistance (case 4-6).Male pigs were used as donors and female pigs as recipients.Food deprivation was induced in pigs for 24 h and water deprivation for 12 h before the operation.This study was approved by the Ethics Committee of Animal Experiments of Xi’an Jiaotong University.

Anesthesia

Animals were given primary anesthesia with an intraperitoneal injection of pentobarbital sodium (20 mg/kg) and ear vein(1 mg/kg).After the animal was placed in the supine position,the limbs were fixed.A gastrointestinal decompression tube was placed via the mouth.After proper fixation, endotracheal intubation was performed using a laryngoscope.The breathing parameters were set for the following breathing mode using highfrequency jet ventilation tidal volume, 10-20 mL/kg; respiratory rate, 16 bpm; inhalation and exhalation ratio (I:E), 1:2; and oxygen concentration, 100%.General anesthesia was maintained with isoflurane (1.5%-5.0%).Preoperative jugular vein catheterizationwas mainly used for intraoperative anesthesia maintenance administration, intraoperative and postoperative fluid replenishment, venous blood collection, and internal carotid artery catheterization to monitor arterial blood pressure.Intraoperative infusion of crystalloid and colloid fluids was used to maintain blood pressure, and vasoactive drugs were administered when necessary.

Fig.2.Loading MVAR for donor liver.A: Repairing diaphragm and SHVC of donor liver; B: SHVC loaded with integrated elliptical MVAR; C: PV loaded with MVAR; D: IHVC loaded with MVAR.MVAR: magnetic vascular anastomosis ring; SHVC: suprahepatic vena cava; PV: portal vein; IHVC: infrahepatic vena cava.

Donor procedure

A cross incision was made along the xiphoid process.Upon entering the abdominal cavity, a surgical retractor was used to ensure sufficient surgical field exposure.The first porta was sufficiently exposed, and the common bile duct was dissociated and ligated.The hepatic artery was dissociated from the celiac trunk, and the other branches were ligated.The PV and the IHVC were exposed clearly, the ligaments around the liver were disconnected, and the second hepatic portal was fully dissociated.Blood collected by the aortic cannula was used in other experiments.

Ice was placed around the liver, and the PV and celiac trunk were intubated and heparinized.The heparinized balanced salt solution was perfused at 4 °C, and the outflow tract was opened.When the color of the liver changed and the outflow fluid became clear, the liver was removed.The diaphragm around the SHVC was preserved, and the IHVC was severed above the diaphragm.The PV was severed at the confluence of the splenic and superior mesenteric veins, and the IHVC was severed 2.5 cm below the liver.The donor liver was removed and placed in a liver repair basin in an ice-water bath.Suitable inner-diameter magnetic rings were selected to match the vessel diameters.The SHVC above the diaphragm was eliminated and the diaphragm was sheared to fit the size of the ring ( Fig.2 A).The SHVC was approached using the “beltization”technique [19], in which 4-0 Prolene was used to suture the vein wall circumferentially along its margin with a 5-mm interval between each stitch.Then, the DMVAR was set into the outer side of the vessels, and the vessels were everted to the undersurface of the DMVAR.The knot was tied to moderate strength, and the magnetic rings were fixed ( Fig.2 B).The PV and IHVC were approached in the same manner as the SHVC ( Fig.2 C, D).

Recipient procedure

A transverse incision of 15-20 cm was made at the fifth or sixth nipple level of the pigs, and a gasless abdominal tractor was established to form a laparoscopic operation space.A 10-mm trocar was established at the intersection between the anterior median line and the fourth or fifth nipple level to place the laparoscope.The other four trocars were established at the intersection between the left or right anterior axillary line and the second or fourth nipple level.The size of the trocars was 5 or 12 mm.The right lobe and part of the intestine of the right upper abdomen and the left lobe were ward offwith abdominal gauze or were pushed aside by the first assistant by holding the gauze with nondestructive forceps.The first porta was successfully exposed.The peritoneum on the surface of the hepatoduodenal ligament was opened, the common bile duct was dissociated and ligated with a titanium clip, and then severed.Lymph nodes present in the ligated hepatoduodenal tissue were dissected.The proper hepatic artery was dissociated and ligated, and the PV was fully exposed.The peritoneum on both sides of the IHVC was opened, and the IHVC was fully dissociated.The perihepatic ductile-band was disconnected.

The left and right phrenic veins were sutured using ligation.The diaphragm above the IHVC was cut open at 2 cm, and the inferior vena cava (IVC) was visible ( Fig.3 A).The IVC was completely dissociated.The block rope was placed around the IVC to occlude the blood flowand then the DSMVAR was placed around the IVC( Fig.3 B).The PV, IHVC, and SHVC were successively occluded.The PV and IHVC were severed at appropriate positions to match the donor liver.The SHVC was severed, and the diaphragm was closed.Finally, the recipient livers were isolated.The RMVAR was loaded under laparoscopy, and the PV and IHVC were placed on the needle of the RMVAR either with totally laparoscope or manual assistance ( Fig.3 C, D).The SHVC was anastomosed with hand assistance ( Fig.3 E), and the IHVC and PV were anastomosed totally using a laparoscopic instrument or manual assistance ( Fig.3 F).Blood flow was reperfused after anastomosis was completed, and the liver was rewarmed.The bile duct was anastomosed end-toend under laparoscopy or hand assistant.The diaphragm and ab-domen were closed, and an ultrasound examination was performed to check for blood flow.One hour after the operation, the animals were sacrificed by sodium pentobarbital overdose, and autopsies were performed.

Fig.3.Loading and anastomosing MVAR for recipient.A: The diaphragm opened lengthwise above the SHVC; B: the gap elliptical MVAR placed around the IVC; C: the recipient’s IHVC loaded with RMVAR; D: the recipient’s PV loaded with RMVAR; E: magnetic anastomosis of SHVC; F: magnetic anastomosis of IHVC and PV.MVAR: magnetic vascular anastomosis ring; SHVC: suprahepatic vena cava; IVC: inferior vena cava; PV: portal vein; IHVC: infrahepatic vena cava; RMVAR: magnetic vascular anastomosis rings for recipient.

Ultrasound examination

Duplex ultrasonography (LMD 2140MD Diagnostic Ultrasound System, SONY CORPORATION, Minato-ku, Tokyo, Japan) was performed immediately after the procedure to evaluate the patency of the anastomotic stoma.

Statistical analysis

An independent samples Student’st-test was used to compare the values between the two groups.All data were expressed as mean ±standard deviation.Statistical significance was set atP<0.05.

Results

Six pigs underwent laparoscopic liver transplantation.The anastomosis of the PV and IHVC was performed totally using the laparoscope in case 1-3 and with manual assistance in case 4-6.Liver transplantation was successfully performed in five cases.Postoperative ultrasonographic examination showed that the portal inflow was smooth, and that no lumen stenosis was detected ( Fig.4 ).However, in case 2, the MAVRs of the PV and IHVC were attached to each other, resulting in PV bending and blood flow obstruction.

The observation data for laparoscopic liver transplant operations for the recipient pigs are shown in Table 1.The cold ischemia time was 89 ±12 min for the laparoscope group and 85 ±7 min for the manual assistance group.The time for loading MVAR for the donor liver was 20 ± 1 min, 8 ± 1 min, and 6 ±1 min for SHVC, IHVC, and PV, respectively, in the laparoscope group, and 18 ± 3 min, 7 ± 2 min, and 5 ±1 min for SHVC, IHVC, and PV, respectively in the manual assistance group.The time for loading MVAR for the recipients of IHVC was 13 ± 2 min and 5 ± 1 min in the laparoscope group and the manual assistance group, respectively(P<0.01).The loading time for the recipients of PV was 10 ±2 min and 4 ±1 min in the laparoscope group and the manual assistance group, respectively (P<0.05).The anastomotic time for SHVC was 2 ± 1 min in the laparoscope group and 3 ± 1 min in the manual assistance group (P>0.05).Anastomotic time for IHVC was 5 ± 1 min vs.1 ± 1 min in the laparoscope group and the manual assistance group (P<0.01), and that for PV was 4 ±1 min vs.1 ± 1 min (P<0.01).The anhepatic phase was 43 ± 4 min in the laparoscope group and 23 ±2 min in the manual assistance group (P<0.01).Operative time and blood loss were not significantly different between the two groups.All ultrasonographic findings showed that the portal inflow was smooth ( Fig.4 ), except in case 2.No lumen stenosis was observed in any of the pigs.During autopsy, we found that the MVAR of the PV and IHVC in case 2 attracted each other, resulting in PV bending and blood flow obstruction.

Table 1The observation data of the laparoscopic liver transplantation for pigs.

Discussion

The improvement in minimally invasive surgery technology [20], video equipment, laparoscopic instrumentation, and richer experience with laparoscopic surgery, has led many hepatobiliary surgeons to attempt laparoscopic treatment of various hepatic diseases [21–23].

Surgeons have gained sufficient knowledge and laparoscopic operational skills to perform laparoscopic procedures for the liver and affiliated conduits.Several cohort studies have suggested that laparoscopic left lateral sectionectomy should be accepted as the standard of care [11].Currently, laparoscopic hemihepatectomy and major resection were reported to be better than open surgery in terms of wound infection rate, blood loss, time to oral intake, and hospital duration, without increased operative time or other complications [ 12 , 24 ].Laparoscopic end-to-end biliary reconstruction and bilio-enteric anastomosis have also been considered safe and feasible [ 25 , 26 ].Laparoscopic arterial reconstruction is a reliable technique [27].Surgeons have sufficient experience with laparoscopic hepatobiliary surgery.Furthermore, anesthesia and nursing for liver transplantation have made great progress over the years [28–30].

Laparoscopic parenchymatous organ transplantation is not a radical procedure.The first report on the performance of a com-plete laparoscopic procedure in a porcine survival model was presented by Meraney et al.[31].The average operative time was 6.2 h.Laparoscopic venous and arterial anastomoses were performed at 33 and 31 min, respectively.Rosales et al.presented the first laparoscopic kidney transplantation for a 69-year-old woman who had no surgical history and was suffering from end-stage renal disease without dialysis in 2010 [14].They used three trocars and a 7-cm Pfannenstiel incision to place a hand-access device.Hoznek et al.was the first to perform a robot-assisted kidney transplantation in humans [32].This initial experience demonstrates the feasibility of robot-assisted kidney transplantation.Studies demonstrated that regional hypothermia could achieve good outcomes in robot-assisted kidney transplantation with a set of guidelines [33–37].Robot-assisted kidney transplantation was associated with lower blood loss, smaller incisions, lower postoperative pain and use of anesthesia, fewer wound complications (0 vs.4%), and fewer symptomatic lymphoceles (0 vs.7%) than open surgery.Graft function, graft rejection rate, and overall graft survival were similar.In summary, minimally invasive surgery has achieved profound development and wide application in the field of kidney transplantation; thus, it is imperative to combine minimally invasive surgery with liver transplantation.

Fig.4.Ultrasonographic scanning vessel inflow.A: Ultrasound image of PV anastomosis stoma; B: ultrasound image of IHVC anastomosis stoma.PV: portal vein; IHVC:infrahepatic vena cava.

However, unlike laparoscopic renal transplantation, laparoscopic liver transplantation has not been performed.Laparoscopic vascular anastomosis is one of the most important operations in laparoscopic liver transplantation.Liver transplantation, especially vascular anastomosis, is a highly time-sensitive procedure, where a long anhepatic period can increase the rate of adverse events [38–40].At present, a variety of vascular anastomosis devices have been used in animal experiments and clinical trials [ 16 , 41-44 ].Obora et al.first reported the use of magnets for anastomosis (MCA) at the ends of blood vessels in 1978 [45].Wang et al.designed a new magnetic compression anastomosis device, which comprised a pair of titanium alloy and neodymium-ferrum-boron magnet composite rings to reconstruct the PV in canines [46].The duration of PV anastomosis was significantly shorter in the MCA group than in the manual suture group (8.16 vs.36.24 min).Angiostenosis or thrombosis did not appear in any of the canines postoperatively, and electron microscope scanning showed that the endovascular intima of MCA anastomosis was smoother and the endothelial cells were more orderly.Liu et.al.designed a new magnetic anastomosis ring and demonstrated the feasibility of magnetic anastomosis in the IVC and arteries of canines, and further confirmed it in canine liver transplantation [ 17 , 18 ].After the modification of the magnetic ring,it was successfully used for major vascular reconstruction among patients undergoing liver transplantation, and the anhepatic duration was reduced to 10.5 min [47].

Liver transplantation has been performed for nearly 50 years [48].However, the “J-shaped incision”or “classic Mercedes incision”has never been replaced by a minimally invasive technique.In this study, we designed a new MVAR for laparoscopic liver transplantation.The RMVAR with a needle was introduced to aid in laparoscopic evagination of recipient vessels.This procedure can dilate the anastomosis and avoid anastomotic stenosis.Proper training was undertaken prior to the procedure for laparoscopic magnetic vascular anastomosis on a training instrument using porcine abdominal organs.At present, it takes less time to use manually assisted MVAR loading and anastomosis of the PV and SHVC than with laparoscopy, the main reason being that there is no special instrument to fix the MVAR and evaginate vessels.In the future, we need to design equivalent instruments to perform a pure laparoscopic operation in a short period of time.In case 2,the two MVARs were attracted together because the repair portal vein was long enough such that the vascular tension was low.In the process of abdominal closure, the movement of organs led to magnet displacement and attraction.In the subsequent cases, we appropriately shortened the PV to ensure appropriate tension in the vessel after anastomosis, which can effectively avoid this problem.

In addition, because the SHVC of pig liver is too short, the same method could not be applied; and thus, we placed a gapmagnetic ring above the diaphragm.We suggest that laparoscopic liver transplantation in humans can be performed using MVAR with needles for anastomosis of SHVC, but further confirmation is needed in cadaver experiments.

We believe that laparoscopic liver transplantation should be performed in the future, initially with either orthotopic liver transplantation or piggyback liver transplantation.We have proposed a potential program for the exploration of laparoscopic liver transplantation, which will further improve and optimize the experimental methods and devices used in this procedure.Its feasibility in humans can be evaluated through cadaver experiments, if necessary, to provide a more reliable basis for clinical promotion.

Acknowledgments

None.

CRediT authorship contribution statement

Zhe Feng:Data curation, Formal analysis, Methodology, Investigation, Project administration, Software, Writing – original draft, Writing –review & editing.Shan-Pei Wang:Investigation, Methodology, Project administration.Hao-Hua Wang:Methodology.Qiang Lu:Methodology.Wei Qiao:Methodology.Kai-Ling Wang:Methodology.Hong-Fan Ding:Methodology.Yue Wang:Methodology.Rong-Feng Wang:Methodology.Ai-Hua Shi:Methodology.Bing-Yi Ren:Methodology.Yu-Nan Jiang:Methodology.Bin He:Methodology.Jia-Wei Yu:Methodology.Rong-Qian Wu:Writing – original draft, Writing – review & editing.Yi Lv:Project administration, Funding acquisition, Supervision, Writing –original draft, Writing –review & editing.

Funding

This work was supported by a grant from the Key R&D Project of Shaanxi Province (No.2020GXLH-Z-001 ).

Ethical approval

This study was approved by the Ethics Committee of the Animal Experiments of Xi’an Jiaotong University.

Competing interest

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.