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SURGICAL MODELS

ovel Magnetic Rings for Rapid Vascular Reconstruction in Canineiver Transplantation Model

. Shi, Y. Lv, B. Wang, Y. Zhang, A. Jiang, J.H. Li, X.F. Zhang, Q.Y. Li, K.W. Meng, C. Liu, L. Yu,nd C.E. Pan

ABSTRACT

Objective. Magnetic rings were used for rapid vascular reconstruction in a canine livertransplantation model.Materials and methods. Thirty-two adult mongrel dogs weighing 13 to 16 kg wererandomly selected as donors or recipients of transplantations. The recipients wererandomly divided into two groups: group A (n � 10) had magnetic rings used for vascularreconstruction without venovenous bypass; group B (n � 6) had vascular reconstructionperformed by continuous suturing with splenojugular venovenous bypass.Results. In group A, the entire operative period was 3.24 � 0.49 hours, the durations ofclamping the portal vein and the infrahepatic vena cava of the recipient were 5.89 � 2.27minutes and 3.89 � 0.73 minutes, respectively. In group B, the entire operative period was4.12 � 0.51 hours with the duration of clamping portal vein and infrahepatic vena cava,28.33 � 6.04 minutes and 12.16 � 3.72 minutes (P � .01 vs group A). In group A, meanarterial pressure dropped during the anhepatic phase but recovered quickly afterreperfusion. The fluid infusion was about 730.56 � 50.56 mL in the group A and a pressoragent was unnecessary. In group B, blood pressure dropped during the anhepatic phaseand slowly recovered. The fluid infusion was about 2241.67 � 390.78 mL and a pressoragent was used to maintain the blood pressure of the recipient. No twist or thrombus wasdiscovered in the anastomoses group A and the endothelium at the site of anastomosis wasentire. In group B, errhysis was common in the anastomotic stomas. Nine of 10 dogs ingroup A survived more than 3 days, the longest being 8 days, whereas four of the six dogsin group B survived less than 3 days.

From the Department of Hepatobiliary Surgery (Y.S., Y.L., B.W.,.Z., A.J., J.H.L., X.F.Z., Q.Y.L., C.L., L.Y., C.E.P.), First Hospital ofi’an Jiao Tong University, China, and Department of Hepatobili-

Address reprint requests to Yuan Shi, PhD, Department ofHepatobiliary Surgery, The First Affiliated Hospital of Xi’anJiao Tong University, 710061 China. E-mail: luyil69@126.com

ry Surgery (K.W.M.), Yan’tai Yuhuangding Hospital, China.

041-1345/06/$–see front matter © 2006 by Elsevier Inc. All rights reserved.oi:10.1016/j.transproceed.2006.08.174 360 Park Avenue South, New York, NY 10010-1710

070 Transplantation Proceedings, 38, 3070–3074 (2006)

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MAGNETIC RINGS FOR VASCULAR RECONSTRUCTION 3071

Conclusion. The results showed that the anhepatic time was significantly shortened(about 5.89 � 2.27 minutes) in group A compared with group B and venovenous bypasswas unnecessary. Magnetic rings could be used for rapid vascular reconstruction in canineliver transplantation model. The long-term results of this procedure should be clarified

before it is applied in clinical practice in the future.

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he needle and thread are still used for vascular anas-tomosis in liver transplantation more or less as Alexis

arrel described 100 years ago.1 However, there are severalisadvantages of suturing. The penetration of the needleroduces vessel wall damage, which affects the healingesponse. Nonabsorbable suture material left as an intralu-inal foreign body may cause an inflammatory reaction,

latalet aggregation, impaired endothelial function, intimalyperplasia, and hence stenosis.2–5 Because hand-sewingakes time and the portal vein and inferior vena cava haveo be clamped for more than 30 minutes during therocedure, one may encounter severe hypotension, hypoxiccidosis, hyperpotassemia, and even renal dysfunction dur-ng the anhepatic phase.6–8 Therefore, in this study we used

agnetic rings with a titanium oxide coating for rapidascular reconstruction in canine liver transplantation. Thenhepatic time was shortened to 5.89 � 2.27 minutes witho need for venovenous bypass.

ATERIALS AND METHODSreparation of Magnetic Rings

agnetic rings of various sizes made from neodymium-ferrum-oron are widely used in dental surgery.9 These rings especiallyoated by a titanium oxide airbrush have a powerful magnetic forcend low noxious property.10 The inner diameter of the magneticings (weighing 0.25 to 0.5 g) is 6 to 15 mm and their outer diameters 9 to 18 mm. The magnetic flux density of the rings is about 68o 92 mT. The diameters of the vessels were measured to selecthe proper fit of the rings, which were sterilized by iodophorolution.

nimals

hirty-two adult mongrel dogs weighing 13 to 16 kg were randomlyelected as 16 donors or 16 recipients. The recipients were ran-

Fig 1. The vein was passed through the magnetic rings. v

omly divided into two groups: group A (n � 10) using magneticings for vascular reconstruction without venovenous bypass; group

(n � 6) using a hand-sewn anastomosis, with a heparin-coatedatheter for splenojugular passive venovenous bypass.

ransplantation Procedure

he operation was performed under general anesthesia with endo-racheal intubation and mechanical ventilation using intravenousdministration of sodium pentobarbital (30 mg/kg) and pancuro-ium bromide (0.1 mg/kg). No immunosuppressive drugs wereiven.

In the donors, the liver was harvested after flushing with 1500 mLf ice-cold Ringer’s lactate and 6000 U of heparin. In group A, theagnetic ring was passed through the suprahepatic inferior vena

ava, which was everted. A purse-string suture fixes the magneticing. The infrahepatic inferior vena cava and portal vein wererepared similarly (Figs 1-4). In group B, the donor livers wererepared as previously discribed.3

The recipient hepatectomy was performed using the methodescribed by Ku et al.4 In group B, a heparin-coated catheter wassed for a splenojugular passive venovenous bypass, while noenovenous bypass was used in group A. The graft was implantedn the orthotopic position with vascular anastomosis performedith magnetic rings in group A as follows: the suprahepatic inferiorena cava, the portal vein, and infrahepatic inferior vena cava (Figs-7). After vascular eversion the magnetic ring was fixed outsidehe vein wall with a purse-string suture. The ends of the donor andecipient vessels were put together to finish the anastomosis.wisted vein stomas were corrected by turning the magnetic ringsfter the vascular anastomosis. We chose antero-right hepatic vein

Fig 2. Purse-string suture.

ig 3. Magnetic rings were inserted into the purse through

ascular ecstrophy, then fixed.

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3072 SHI, LV, WANG ET AL

s the 11 o’clock point to avoid suprahepatic inferior vena cavawisting, and chose supraloric vein as 0 o’clock point to avoid portalein twisting. We even could correct twisted stomas by revolvinghe magnetic rings after reperfusion. The reconstruction of vesselsn group B was performed by suturing as previously described.

The hepatic artery reconstruction was performed by an end-to-nd anastomosis in the recipient. Finally, the donor celiac axis orommon hepatic artery and the recipient common hepatic arteryere anastomosised in end-to-end fashion by hand-sewing.

ESULTS

peration time is shown in Table 1.

ean Arterial Pressure Changes

n group A, mean arterial pressure dropped during thenhepatic phase but recovered quickly after reperfusion.he fluid infusion was about 730.56 � 150.56 mL in groupand a pressor agent was not necessary. In group B, blood

ressure dropped during the anhepatic phase only slowlyecovering (Fig 8). The fluid infusion was about 2241.67 �90.78 mL and a pressor agent was required in group Becipients.

nastomosis Site

y the autopsy of the animals in the two groups, no errhysis,wist or thromus was detected. The endothelium at the sitef anastomosis was intact (Figs 9-10). In group B, frequencyf errhysis, twist and thromus at the site of anastomosis washarply higher than that in group A.

Fig 4. The superahepatic inferior vena cava magnetic rings.

Fig 5. Magnetic rings for superahepatic inferior vena cava.

Graft survival is described in Table 2; all grafts wereventually lost due to rejection or other causes.

ISCUSSION

cclusion of portal vein and infrahepatic inferior vena cavaor more than 20 to 30 minutes is known to lead to severeypotension, hypoxic acidosis, hyperpotassemia, cardiacrrhythmia, and death in canine orthotopic liver transplan-ation.11 It is difficult to complete the anastomosis duringhis time. So, a venovenous bypass is necessary. However,enovenous bypass has been abandoned in most liverransplantation centers in the world due to the shortcom-ngs of pulmonary embolism, pipe embolism, hepariniza-ion, prolonged operation time, and so on.12–14 Mondent al reported the cuff method to perform the venousnastomosis in canine liver transplantation without veno-enous bypass; the anhepatic time was less than 15 min-tes.15 Although it is attractive, Fumitaka et al did notelieve that this method significantly shortened the anhe-atic time (around 25 to 30 minutes).16 Thus cuffed ringechnique did not gain clinical application.

In 1978 Yoshiro Obora first described a method foremoral and carotid artery anastomosis of dogs and ratsased on the force between two matching magnetic ringssing a cogwheel-shaped hollow metal instrument withix spurs.17 Histological continuity of the vascular wallas confirmed 20 days after the anastomosis. There was

Fig 6. Magnetic ring anastomosis.

Fig 7. After reperfusion.

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MAGNETIC RINGS FOR VASCULAR RECONSTRUCTION 3073

ardly any foreign body reaction or inflammation at thenastomosis site. Neither necrosis nor thickening of theascular wall was evident at 180 days after the procedure.n this experiment, neodymium-ferrum-boron was cho-en to make the rings. The rings have a powerfulagnetic force and low noxious property. They were

oated with titanium oxide for safety and biocompatibil-ty.

The results showed that the anhepatic time was signif-cantly shortened (about 5.89 � 2.27 minutes) in group Aompared with group B and a venovenous bypass was notecessary. The endothelium at the anastomosis site was

ntact. There was no errhysis, twist, or thrombus detectedn group A. The anastomosis time for infrahepatic vena

Fig 8. MAP changes.

ig 9. Inside overlook of suprahepatic inferior vena cava anas-omosis site after reperfusion.

Table 1. Operation Time

Group A Group B

otal operation time (h) 3.24 � 0.49 4.12 � 0.51*old ischemia time (h) 1.21 � 0.37 1.32 � 0.14**uprahepatic inferior vena cava(min)

3.15 � 1.16 16.32 � 5.12*

nhepatic time (min) 5.89 � 2.27 28.33 � 6.04*nfrahepatic inferior vena cava (min) 3.89 � 0.73 12.16 � 3.72*

*P � .01 vs group A.**P � .05 vs group A.

ava was only 3.89 � 0.73 minutes when magnetic rings t

ig 10. Inside overlook of suprahepatic inferior vena cava

ig 11. (1) Slots for anastomosis; (2) dismantling slots; (3) slope

Table 2. Survival, Cause of Death, and Vascular Pantencyat Anastomosis

DogNo.

Survival(d) Cause of Death

Vein AnastomosisPantency

1 7 Rejection Patent2 5 Infection Patent3 3 Hepatic artery thrombosis Patent4 6 Rejection Patent5 7 Rejection Patent6 12 h Anesthetic accident Patent7 6 Rejection Patent8 5 Pneumonia Patent9 8 Rejection Patent10 3 Unknown Patent1 5 Rejection Patent2 1 Errhysis at anastomic

stomaAnastomotic stomal

leak3 2 Portal vein thrombosis Portal vein thrombosis4 12 h Errhysis at anastomic

stomaPortal vein twist and

leak5 6 Rejection Patent6 1 Errhysis at anastomic Anastomotic stomal

o prevent endothelial damage.

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ere applied, and the hemodynamics were stable. Also,n anastomosis with magnetic rings could even be per-ormed by junior surgeons.

However, the rings used in the experiment have to be leftn the canine abdominal cavity, and the anastomotic stomaas rigid and poorly compliant. About 4 cm had to be leftetween the portal vein and infrahepatic inferior vena cavanastomosis sites to avoid the attraction of the rings.ong-term results must be defined; however, dismantling

he magnetic rings (Fig 11) might resolve the potentialroblems mentioned above. Further study must be performo assess future clinical applications.

EFERENCES

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eedles and suture. J Neurosurg 53:32, 19803. Morito Monden MD, Richard H, Barters JG, et al: A simpleethod of orthotopic liver transplantation in dogs. Ann Surg

95:110, 19824. Ku Y, Maekawa Y, Tominaga M, et al: Suprahepatic vena

ava anastomosis of the donor liver to the recipient retrohepaticena cava in canine liver transplantation. Eu Surg Res 24:155, 1992

5. Zeebregts CJAM, van den Dungen JJAM, Kalicharan D,t al: Nonpenetrating vascular clips for small-caliber anastomos.

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6. Nakasuji M, Bookallil MJ, Asada A, et al: Causes of renalysfunction during the anhepatic phase in patients for orthotopic

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unction during orthotopic liver transplantation. Minerva Anest-siol 63:221, 1997

8. Schwarz B, Pomaroli A, Hoermann C, et al: Liver transplan-ation without venovenous bypass: morbidity and mortality inatients with greater than 50% reduction in cardiac output afterena cava clamping. J Cardiothorac Vasc Anesth 15:460, 2001

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ion with preservation of the inferior vena cava. Ann Surg 210:649,98913. Fleitas MG, Casanova D, Martino E, et al: Could the

iggyback operation in liver transplantation be routinely used.rch Surg 129:842, 199414. Cherqui D, Lauzet JY, Rotman N, et al: Orthotopic liver

ransplantation with preservation of the caval and portal flows.ransplantation 58:793, 199415. Monden M, Barters RH, Fortner JG: A simple method of

rthotopic liver transplantation in dogs. Ann Surg 195:110, 198216. Oike Fumitaka, Uryuhara Kenji, Otsuka Masayuki, et al:

iver Transplantation 71:328, 200117. Obora Y, Tamaki N, Matsumoto S: Nonsuture microvascu-

ar anastomosis using magnet rings: preliminary report. Surg

eurol 9:117, 1978