Novel magnetic rings for rapid vascular reconstruction in canine liver transplantation model

Shortening the recipient warm ischemia time could be a strategy for expanding the liver donor pool

BACKGROUND

Shortening the recipient warm ischemia time (rWIT) has been proven to be effective for improving the short- and long-term outcomes after liver transplantation (LT) and offsets the negative impact of an extended cold ischemia time. However, few studies have been conducted to explore the prognostic effects of shortening the rWIT in transplantations using a liver graft from an extended-criteria donor (ECD).

AIM

To investigate whether shortening the rWIT could improve the outcomes of ECD LT.

METHODS

Rat ECD autologous orthotopic LT were performed with variable rWITs (0, 10, 20, and 30 minutes). Near-infrared fluorescence imaging (FI) was used for the real-time assessment of liver graft ischemia-reperfusion injury after the anhepatic phase. Survival was assessed, and liver function and histological analyses were performed on the third day after transplantation.

RESULTS

The FI curve growth rate and postoperative three-day survival rate significantly increased, and the liver function and Suzuki score of the liver grafts significantly improved when the rWIT was ≤ 10 minutes (P < 0.05).

CONCLUSION

The post-transplant outcomes were significantly better with a shorter rWIT (10 minutes or less) than with a longer rWIT, which could be a strategy for expanding the liver donor pool.

Laparoscopic-assisted full-sized liver transplantation with magnetically fast portal vein anastomosis: an initial cohort study

BACKGROUND

Some cases of laparoscopic-assisted liver transplantation (LA-LT) with utilization of reduced-size grafts has been reported. The authors here introduced successful utilization of LA-LT with whole liver grafts and magnetic portal vein anastomosis.

METHODS

Eight patients with liver cirrhosis were included for LA-LT using donor organs after cardiac death. The surgical procedures included purely laparoscopic explant hepatectomy and whole-liver graft implantation via the midline incision. After explant removal, the whole-liver graft was then placed in situ, and a side-to-side cavo-caval anastomosis with 4-5 cm oval opening was performed. The magnetic rings were everted on the donor and recipient portal vein, respectively, and the instant attachment of the two magnets at the donor and recipient portal vein allowed fast blood reperfusion, followed by continuous suturing on the surface of the magnets.

RESULTS

The median operation time was 495 (range 420-630). The median time of explant hepatectomy and inferior vena cava anastomosis was 239 (range 150-300) min and 14.5 (range 10-19) min, respectively. Of note, the median anhepatic time was 25 (range 20-35) min. All the patients were discharged home with no major complications after more than 12 months follow-up.

CONCLUSION

LA-LT with full-size graft is feasible and utilization of magnetic anastomosis would further simplify the procedure.

Research progress on anatomy reconstruction of rat orthotopic liver transplantation

Rat orthotopic liver transplantation (ROLT) serves as an ideal animal model and has gained popularity in addressing complications and perioperative treatments related to clinical liver transplantation. Through extensive research on ROLT model construction, the conventional "two-cuff" method has gradually become established. However, traditional methods still present challenges including limited visual field during vascular suturing, vascular torsion, biliary tract injuries, and prolonged anhepatic periods. Consequently, this paper aims to review the latest advancements and various techniques in this field, providing a valuable reference for individuals interested in constructing ROLT models.

Liver transplantation using magnetic anastomosis in pigs

Magnetic anastomosis substantially shortens the duration of vascular anastomosis. We aimed to apply magnetic anastomosis technology (MAT) to donor liver implantations in pig orthotopic liver transplantation (OLT). Twenty healthy adult pigs were randomly divided into donors and recipients, and major vascular anastomosis was performed using MAT during OLT. Recipient liver and kidney function was measured pre-surgery and 12, 24 and 72 h post-surgery. Vascular anastomoses examinations were performed using ultrasound or angiography weekly post-surgery, and pathological examinations of vascular anastomoses were performed during autopsy after animal euthanasia. All recipients survived 24 h after surgery, which is considered as successful transplantation. Anhepatic duration was only 13 min, and no anastomotic obstruction or stenosis, magnetic displacement and anastomotic angulation, or distortion was found upon postoperative examinations of major liver vasculature. Aspartate aminotransferase, alanine aminotransferase, and total bilirubin serum levels increased considerably postoperatively. The follow-up period for this study was 1 year, and the median survival time of all recipients was 115 d (interquartile range = 11-180 d). The main causes of death were liver failure, immune rejection, infection, and arterial anastomotic bleeding. Moreover, vascular anastomoses healed well with a survival time of more than two weeks. We developed a novel magnetic device to create a fast and safe technique to perform major vascular anastomoses in pig liver transplantations. Additionally, the liver graft implantation using MAT considerably shortened the recipient warm ischemia time, which will reduce the extent of ischemia-reperfusion injury. We conclude that MAT is an effective method for donor liver fast implantation in OLT in pigs.

A novel magnetic compression technique for cystostomy in rabbits

Magnetic compression technique (MCT) is a popular new anastomosis method. In this paper, we aimed to explore the feasibility of use of MCT for performing cystotomy in rabbits. The parent magnets and daughter magnets for rabbit cystostomy were designed and manufactured according to the anatomical characteristics of rabbit lower urinary tract. Twelve female New Zealand rabbits were used as animal models. After anesthesia, a daughter magnet was inserted into the bladder through the urethra, and the parent magnet was placed on the body surface projection of the bladder over the abdominal wall. The two magnets automatically attract each other. Postoperatively, the state of magnets was monitored daily, and the time when the magnets fell off was recorded. Cystostomy with MCT was successfully performed in all twelve rabbits. The mean operation time was 4.46 ± 0.75 min. The magnets fell off from the abdominal wall after a mean duration of 10.08 ± 1.62 days, resulting in the formation of bladder fistula. Macroscopic and microscopic examination showed that the fistula was well formed and unobstructed. The junction between bladder and abdominal wall was tight and smooth. We provide preliminary experimental evidence of the safety and feasibility of cystostomy based on MCT.

End-to-end vascular anastomosis using a novel magnetic compression device in rabbits: a preliminary study

Magnetic compression anastomosis (MCA) has been appreciated as an innovative alternative to manual suturing in vascular reconstruction. However, magnetic devices have limitations in their applications. The present study aimed to introduce a newly developed magnetic device for end-to-end vascular anastomosis. Twenty male New Zealand rabbits were randomly assigned to receive end-to-end postcaval vein anastomosis using either a newly designed MCA device (Group MCA) or continuous-interrupted suturing (Group CIS). The anastomotic patency was evaluated by Doppler or venography immediately, 1 week, and 12 weeks after surgery. Anastomotic quality was evaluated gross and microscopic histological study 12 weeks after surgery. The procedure was successfully performed and all animals survived until sacrifice. The duration of surgery and anastomosis time in Group MCA were significantly shorter compared to Group CIS (all p < 0.001), and the incidence of anastomotic patency and postoperative morbidity were comparable between the two groups (all p > 0.05). Hematoxylin-eosin staining showed that anastomotic intima from Group MCA was much smoother with more regularly arranged endothelial cells than from compared to the Group CIS. A novel MCA device was successfully applied in rabbit vascular anastomosis. We demonstrated the reliability and effectiveness of this newly developed MCA in this study.

Magnetic Anastomosis Rings to Create Portacaval Shunt in a Canine Model of Portal Hypertension

PURPOSE

This study evaluated a novel magnetic compression technique (magnamosis) for creating a portacaval shunt in a canine model of portal hypertension, relative to traditional manual suture.

METHODS

Portal hypertension was induced in 18 dogs by partial ligation of the portal vein (baseline). Six weeks later, extrahepatic portacaval shunt implantation was performed with either magnetic anastomosis rings, or traditional manual suture (n = 9, each). The two groups were compared for operative time, portal vein pressure, and serum biochemical indices. Twenty-four weeks post-implantation, the established anastomoses were evaluated by color Doppler imaging, venography, and gross and microscopic histological examinations.

RESULTS

Anastomotic leakage did not occur in either group. The operative time to complete the anastomosis for magnamosis (4.12 ± 1.04 min) was significantly less than that needed for manual suture (24.47 ± 4.89 min, P < 0.01). The portal vein pressure in the magnamosis group was more stable than that in the manual suture group. The blood ammonia level at the end of the 24-week post-implantation observation period was significantly lower in the magnamosis group than in the manual suture group. Gross and microscopic histological examinations revealed that better smoothness and continuity of the vascular intima had been achieved via magnamosis than with manual suture.

CONCLUSION

Magnamosis was superior to manual suture for the creation of a portacaval shunt in this canine model of portal hypertension.

Novel magnetic compression technique for establishment of a canine model of tracheoesophageal fistula

BACKGROUND

Clinically, tracheoesophageal fistula (TEF) is lack of effective surgical strategies. One reason is due to the lack of appropriate animal models of acquired TEF, which is usually complex and difficult. Recently, the magnetic compression technique has been applied for digestive tract anastomosis or vascular anastomosis in animals. In this study, an animal model of TEF in dogs was developed by using the magnetic compression technique, hoping to provide a new method for mimicking TEF.

AIM

To establish a TEF model in dogs by using the magnetic compression technique.

METHODS

Six male beagles were used as models with two Nd-Fe-B permanent magnets for TEF. The parent magnet and the daughter magnet were placed in the cervical esophagus and trachea, respectively. The anterior wall of the esophagus and the posterior wall of the trachea were compressed when the two magnets coupled. After 4-6 d, the necrotic tissue between the two magnets fell off and the parent and daughter magnets disengaged from the target location, leaving a fistula. Gastroscopy/bronchoscopy, upper gastrointestinal contrast study, and histological analysis were performed.

RESULTS

The establishment of the TEF model in all six beagles was successful. The average time of magnet placement was 4.33 ± 1.11 min (range, 3-7 min). Mean time for the magnets to disengage from the target location was 4.67 ± 0.75 d (range, 4-6 d). TEFs were observed by gastroscopy/bronchoscopy and esophageal angiography. The gross anatomical structure of the esophagus and the trachea was in good condition. There was no esophageal mucosa or pseudostratified ciliated columnar epithelium at the site of the fistula according to histological analysis.

CONCLUSION

It is simple, feasible, and minimally invasive to use the magnetic compression technique for the establishment of the TEF model in dogs.

Magnetic compression anastomosis for biliojejunostomy and pancreaticojejunostomy in Whipple's procedure: An initial clinical study

BACKGROUND AND AIM

Magnetic anastomosis has been attempted in biliary and intestinal reconstruction. The objective of the current study was to introduce an initial clinical use of magnetic compression anastomosis for pancreaticojejunostomy and biliojejunostomy in Whipple's procedure.

METHODS

Patients with peri-ampullary carcinoma and dilated bile and pancreatic ducts were prospectively enrolled from 2016 to 2017. After pancreaticoduodenectomy, an appropriate mother magnet and drainage tube was placed in the proximal bile duct and pancreatic duct. The daughter magnets were introduced to mate with the mother magnets at the anastomotic sites. A close postoperative surveillance and routine cholangiopancreaticography via the drainage tube were performed.

RESULTS

One female and three male patients with a median age of 69 years (range, 57-77) were included. The diameter of the common bile ducts and pancreatic ducts ranged from 8 to 15 mm, and 7 to 10 mm, respectively. The median time duration for biliojejunostomy and pancreaticojejunostomy was 7 (range, 5-8 min) min and 9 (range, 8-10 min) min, respectively. The median time of biliojejunostomy and pancreaticojejunostomy formation was 17 (range, 15-21 days) days and 11 (range, 10-18 days), respectively. With a median follow up of 313 days, one patient developed biliary anastomotic stricture at 11 months after surgery, and underwent stent placement via percutaneous transhepatic drainage sinus, and recovered well.

CONCLUSIONS

Magnetic anastomosis is safe, effective, and simple for both biliojejunostomy and pancreaticojejunostomy in Whipple's procedure.

Fast magnetic reconstruction of the portal vein with allogeneic blood vessels in canines

BACKGROUND

The resection and reconstruction of large vessels, including the portal vein, are frequently needed in tumor resection. Warm ischemia before reconstruction might have deleterious effects on the function of some vital organs and therefore, how to reconstruct the vessels quickly after resection is extremely important. The present study was to introduce a new type of magnetic compression anastomosis (MCA) device to establish a quick non-suture anastomosis of the portal vein after resection in canines.

METHODS

The new MCA device consists of a pair of titanium alloy and neodymium-ferrum-boron magnet (Ti-NdFeB) composite rings. The NdFeB magnetic ring as a core of the device was hermetically sealed inside the biomedical titanium alloy case. Twelve canines were divided into two groups: a MCA group in which the end-to-end anastomoses was made with a new device after resection in the portal vein and a traditional manual suture (TMS) group consisted of 6 canines. The anastomosis time, anastomotic patency and quality were investigated at week 24 postoperatively.

RESULTS

The portal vein was reconstructed successfully in all of the animals and they all survived. The duration of portal vein anastomosis was significantly shorter in the MCA group than in the TMS group (8.16+/-1.25 vs 36.24+/-2.17 min, P<0.05). Portography and ultrasound showed that the blood flow was normal without angiostenosis or thrombosis in all of the canines. Hematoxylin-eosin staining and electron microscope scanning showed in contrast to the TMS group, MCA anastomotic intimal was much smoother with more regularly arranged endothelial cells at week 24 postoperatively.

CONCLUSIONS

The Ti-NdFeB composite MCA device was applicable in reconstruction of large vessels after resection. This device was easy to use and the anastomosis was functionally better than the traditional sutured anastomosis.

Magnetic ring anastomosis of suprahepatic vena cava: novel technique for liver transplantation in rat

To improve the technique of suprahepatic vena cava (SHVC) reconstruction in rat OLT, novel magnetic rings were designed and manufactured to facilitate reconstruction of SHVC and shorten the anhepatic time. One-hundred and twenty adult male Wistar rats were randomly divided into two groups: rings group (n = 30), using magnetic rings for SHVC reconstruction; suture group (n = 30), 7/0 prolene suture was used for SHVC running anastomosis as control. Cuff techniques were used for portal vein and infrahepatic vena cava reconstruction as Kamada and Calne described. The bile duct was reconnected with a stent. The hepatic re-arterialization was omitted. In the rings group, the SHVC reconstruction took 0.91 ± 0.24 (mean ± SD) min; the anhepatic phase and the recipient operation time were 5.63 ± 0.65 min and 36.02 ± 8.02 min, respectively. In suture group, the anastomotic time of SHVC was 10.40 ± 2.11 min; the anhepatic phase and the recipient operation time were 17.76 ± 2.51 and 49.38 ± 12.06 min, respectively, and there was statistically significant difference between the two groups. The ALT levels reached peak at 24 h post-OLT (186.2 ± 32.5 IU/l) and restored to normal level at 96 h gradually. In the rings group, 29 of 30 rats survived at day 7 and 28 of 30 rats survived at day 30. In contrast, only 25 of 30 recipients in suture group remained alive at day 7 and 22 of 30 remained alive at day 30 (P < 0.05). Better anastomotic healing was founded in rings group by pathology and scanning electron microscope. The magnetic rings technique provides a novel, simple method for SHVC reconstruction of OLT in rat. It significantly shortens anhepatic phase, while the success rate of the operation is satisfactory.

Establishment of a simple living donor liver transplantation dog model using a two-step nonvenous bypass hepatectomy

AIM

Dogs are an ideal model for studying living donor liver transplantation (LDLT). However, due to their poor tolerance to congestion and acidosis during portal vein blockage, current LDLT dog models with long operation times have high mortality. To address the issue, we designed a novel simplified operation with two-step nonvenous bypass (NVB) hepatectomy.

METHODS

Eighty dogs were evenly randomized to the living liver donor (LLD) or the recipient (LLR) groups. A standard lobectomy of I, II, and III lobes was performed in the LLD group. In the LLR group, first only I, II, and III lobes were resected using NVB; the residual lobes were resected off just after donor lobes were implanted.

RESULTS

For the LLD group, the operation time was 172.67 ± 20.98 minutes, amount of blood loss was 71.39 ± 13.59 mL, and 2-week survival rate was 85.00%. For the LLR group, the operation time was 251.61 ± 22.87 minutes, amount of blood loss was 220.00 ± 96.40 mL, amount of blood transfusion was 163.89 ± 44.74 mL, and 48-hour survival rate was 77.14%. In the LLR group, the mean arterial and central venous pressures decreased after organ implantion, but gradually recovered to normal levels after surgery. The liver function biochemical parameters recovered to preoperational levels after 14 days in the LLD group; in the LLR group, they gradually increased during 48 hours after operation.

CONCLUSION

The present method with two-step NVB hepatectomy can be used efficiently and safely for establishing LDLT dog model.

Portacaval shunt established in six dogs using magnetic compression technique

BACKGROUND AND AIMS

Installing the transjugular intrahepatic portosystemic shunt for portal hypertension is relatively safe, but complications are still high. To explore a new method of portacaval shunt, the magnetic compression technique was introduced into the shunting procedure.

METHODS

A portal-inferior vena cava shunt was performed on 6 male mongrel dogs by two hemocompatible Nd-Fe-B permanent magnets, parent and daughter. The parent magnet was applied to the inferior vena cava guided by a catheter through the femoral vein. The daughter magnet was moved to the anastomosis position on the portal vein with a balloon catheter through the splenic vein. After the daughter magnet reached the target position, the two magnets acted to compress the vessel wall and hold it in place. Five to 7 days later, under X-ray guidance, the magnets were detached from the vessel wall with a rosch-uchida transjugular liver access set. One month later, histological analysis and portal venography were performed.

RESULTS

5-7 days after the first surgery, a mild intimal hyperplasia in the portal vein and the inferior vena cava, and continuity of the vascular adventitia from the portal vein to the inferior vena cava as observed. During the second surgery, the contrast media could be observed flowing from the portal vein into the inferior vena cava. Portal venography revealed that the portosystemic shunt was still present one month after the second surgery.

CONCLUSIONS

Magnamosis via a device of novel design was successfully used to establish a portacaval shunt in dogs.

Portacaval shunt established in six dogs using magnetic compression technique

BACKGROUND AND AIMS

Installing the transjugular intrahepatic portosystemic shunt for portal hypertension is relatively safe, but complications are still high. To explore a new method of portacaval shunt, the magnetic compression technique was introduced into the shunting procedure.

METHODS

A portal-inferior vena cava shunt was performed on 6 male mongrel dogs by two hemocompatible Nd-Fe-B permanent magnets, parent and daughter. The parent magnet was applied to the inferior vena cava guided by a catheter through the femoral vein. The daughter magnet was moved to the anastomosis position on the portal vein with a balloon catheter through the splenic vein. After the daughter magnet reached the target position, the two magnets acted to compress the vessel wall and hold it in place. Five to 7 days later, under X-ray guidance, the magnets were detached from the vessel wall with a rosch-uchida transjugular liver access set. One month later, histological analysis and portal venography were performed.

RESULTS

5-7 days after the first surgery, a mild intimal hyperplasia in the portal vein and the inferior vena cava, and continuity of the vascular adventitia from the portal vein to the inferior vena cava as observed. During the second surgery, the contrast media could be observed flowing from the portal vein into the inferior vena cava. Portal venography revealed that the portosystemic shunt was still present one month after the second surgery.

CONCLUSIONS

Magnamosis via a device of novel design was successfully used to establish a portacaval shunt in dogs.

Causes of intra-abdominal hemorrhage in rhesus monkeys after liver transplantation

AIM: To analyze the causes of abdominal hemorrhage in rhesus monkeys after liver transplantation.

METHODS: Healthy male rhesus monkeys weighing 7.2-11.5 kg were used as recipients, while healthy females or males weighing 5.3-8.1 kg were use as donors. Donor operation was performed quickly by making a big crucial incision in the abdomen. The improved dual-cuff of the portal vein and inferior vena cava was completed except for keeping biliary support tube within the donor liver. Classical orthotopic liver transplantation was performed in recipients.

RESULTS: Classical orthotopic liver transplantation was successful in all 25 rhesus monkeys. Eleven rhesus monkeys suffered from abdominal hemorrhage in the early postoperative stage, and 5 of them died. The distribution of abdominal hemorrhage site was as follows: anastomotic hemorrhage of the inferior vena cava in 5 cases, anastomotic hemorrhage of the portal vein in 5 cases, anastomotic hemorrhage of the superior vena cava in 4 cases, anastomotic hemorrhage of the liver bed in 4 cases, hemorrhage from mechanical injury in 3 cases, subcapsular hemorrhage of the liver in 3 cases, and hemorrhage of the right suprarenal vein and lumbar vein in 2 cases.

CONCLUSION: The most common cause of abdominal hemorrhage in rhesus monkeys after classical orthotopic liver transplantation is anastomotic hemorrhage of the inferior vena cava and portal vein.