Dorsal penile vein as a new training model for microvenous anastomosis in rats

The authors present a new model for microsurgical training of venous anastomosis-namely, the dorsal penile vein of the rat. In 12 male Wistar rats weighing 220 to 290 g, the anatomy of the dorsal penile vein was studied by dissection and histology. Anatomic dissection studies revealed that the dorsal penile vein has an average diameter of 1.4 mm (range, 1.2-1.6 mm) without tendency to collapse. The vein could be dissected for an average segment of 25 mm without any branches, allowing easy dissection and approximator clamp placement. Comparison of its cross-section with that of the femoral vein histologically by light microscopy and scanning electron microscopy revealed a larger diameter and much thicker vessel wall with a prominent tunica media and adventitia. Based on the findings of the anatomic study, the dorsal penile vein anastomotic model was created in the rat. In 20 animals, the vein was divided sharply in its midsection and was anastomosed end-to-end using standard microsurgical technique. Results indicated a 100% patency rate immediately after the anastomosis and a 90% patency rate (18 of 20) 1 week after the procedure. This model offers the advantages of easy dissection without ligation of any side branches and a thick vessel wall without a tendency to collapse. Moreover, a major limb vein is not sacrificed. It is concluded that this new model may better simulate the clinical procedure of microvenous anastomosis because it presents similarities to human veins.     

Investigating human microskin grafting technique in a new experimental model

Background

. Microskin graft technique is a possible solution for treating major burns. The goal of this study was to investigate microskin graft techniques using a new model of grafting human skin onto athymic nude mice.

Materials and methods

Twenty female nude mice were randomly divided into a research group and a control group (14 mice in the research group, six in the control group). On the 11th day after the procedure, the following parameters were investigated: percentage of epithelial coverage, degree of contracture, thickness of the epidermis, thickness of the dermis, number of blood vessels, number of melanocytes.

Results

The healing rate (epithelial coverage) of the wounds was an average of 100% (±0%) in the control group and 97% (±5%) in the research group (P > 0.05). The average degree of wound contraction in the control group was 30% compared to 63% in the research group (P < 0.01). The average thickness of the epidermis formed at the grafted site was 8.17 (±1.94)μm in the control group compared to 4.45 (±4.17)μm in the research group, at the wound margins (P > 0.05).

Conclusion

We found that the microskin graft, created by grinding a sheet of human skin, remained vital, and tissue of human origin was present at the grafted site. Our study shows that this novel method is feasible and has the advantage of enabling investigation of human skin on an animal model. Significant contracture appears to be a drawback of this technique, and we feel that the method should be improved before its clinical application on patients.     

The precise technique of end-to-side microvascular anastomosis with a suitable experimental model.

In order to perform extracranial to intracranial microrevascularisation a good end-to-side microvascular anastomosis technique is the first essential. The rabbit femoral vessels are similar in size to the human cortical branches of the middle meningeal artery and superficial temporal artery and an easy technique of end-to-side anastomosis of these vessels is described. This pays particular attention to proof of patency until the last stitch is applied. Assessment of patency in all three directions is checked by the directional Doppler or the electromagnetic flow probe.     

The effects of preservation on microvascular vein grafts in rats

Segments 15 mm in length were excised from the femoral veins of rats and preserved by refrigeration at 4 C in lactated Ringer's solution for periods up to 21 days. The findings show that veins can be preserved for up to seven days and successfully grafted to recipients. Although there was some success in preserving vein segments for more than seven days, a high rate of thrombosis occurred after implantation in the recipients. It is generally accepted that damaged endothelium causes thrombosis. The light and electron microscopic observations in this study, however, suggest that the condition of the endothelium may not be the only important factor in the patency of small vessels. A thickened and prominent elastic lamina may also play a role in keeping the lumen open.     

The microsurgical triple clamp: a technique for microvascular grafting of short interposition grafts

The microsurgical triple clamp has been developed for use when grafting arteries and veins. Advantages are that the grafting technique can be performed by one person, that the clamp anchors the graft so that quick yet accurate anastomoses can be performed, and that visualization of the back wall is possible throughout the anastomosis.     

Rat tail replantation as a training model for microvascular procedures of digit replantation

In this study we sought to evaluate the potential of rat tail replantation as a tool for very-small-vessel microvascular anastomoses. We used 10 adult Sprague-Dawley rats. The tail was completely amputated 2.0-cm distal to the base of the tail. Then the tail was replanted with anastomoses of two superficial dorsal veins from both sides and one artery. All 10 replanted tails were pink, viable, and normal-appearing at all daily inspections performed from the first to the fourteenth postoperative days. This model can provide a training tool for the acquisition of superior microvascular surgical technique for the repair of very small vessels that stimulate digital replantation. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:364–367, 1998     

Effect of desmopressin on vein graft patency in a microvascular model

Desmopressin acetate decreases blood loss after cardiac surgery by activating platelets. We studied whether this effect was detrimental to small-caliber vein grafts in rats. Thirty minutes before femoral artery grafting with 0.75-mm-diameter reverse autogenous saphenous vein grafts, 20 rats received desmopressin acetate intravenously at 1.0 micrograms/kg over 10 minutes, and 20 control rats received normal saline intravenously over 10 minutes. In each group, 10 rats received a 6-mm-long graft and 10 an 18-mm-long graft. Graft patency was evaluated at 20 minutes, 24 hours, and 30 days. Intimal thickening was assessed by light and scanning electron microscopy. At 30 days, 9 short grafts and 8 long grafts in the desmopressin-treated group were patent, whereas only 8 short control grafts and only 6 long control grafts were patent. Intimal thickening and platelet deposition were the same in both groups. These data show no detrimental effects of desmopressin acetate on saphenous vein graft patency.     

Posterolateral cervical vein as a recipient vein in reconstructive microvascular surgery of the head and neck

Free flaps are becoming the preferred method of choice for head and neck reconstruction. However, many patients who have undergone radiotherapy and radical neck dissection or who require treatment for recurrent tumor, often present difficulty in choosing recipient vessels. The authors have noted a potential recipient vein coursing vertically along the anterior ridge of the trapezius muscle. They used this vein as the recipient vein in two patients; the two free flaps were transferred successfully without complications. This vein, which they provisionally named the posterolateral cervical vein (PLCV), is considered an important option as a recipient vein in head and neck reconstruction when more commonly used recipient cervical veins are unavailable.     

The success of in situ vein grafting: early results in comparison with the reversed vein technique

In a 6-year retrospective analysis of 341 consecutive femorodistal autogenous vein bypasses, results from 104 in situ veins (IS) were compared with 209 reversed veins (RV). The groups were comparable for age, sex, diabetes, indication for surgery and calf vessel run-off, but a significantly higher proportion of the in situ group had a lower distal anastomosis (16% IS, 6% RV, chi 2 = 7.1 P less than 0.01). Overall, operative mortality was 2% and early graft failure was similar in both groups (11% IS, 12% RV, P = NS). Cumulative graft patency rates were 74% IS, 79% RV at one year and 71% IS, 71% RV (P = NS) at three years. Cumulative limb survival rates were 81% IS, 85% RV at one year and 79% IS, 81% RV [P = NS) at 3 years. These results demonstrate that the in situ technique has been used in a wider variety of patients and yielded similar early and intermediate term results to reversed vein.     

The back-approach technique of endoscopic saphenous vein harvesting in coronary artery bypass grafting

PurposeOne of the concerns during endoscopic saphenous vein harvesting (EVH) in coronary artery bypass grafting (CABG) is injury to the vein or its branches. The cutting edge of bipolar electrocautery scissors, used to divide the side branches of the saphenous vein, can cause vascular injury leading to reduced graft patency. We have developed a novel back-approach technique using a C-ring to divide the wide side branches of the saphenous vein during EVH. The aim of the study was to describe the technique and assess early outcomes of EVH using this technique. The back-approach technique is as follows: (a) insert the C-ring near the target branch, (b) push the C-ring over the proximal aspect of the target branch, (c) twist the C-ring forward to capture the target branch, and (d) cut the target branch by bipolar electrocautery.MethodsWe investigated 169 patients, including 35 women (mean age 70.1 ± 8.9 years), who underwent CABG at our hospital, using a novel EVH technique. The patients were categorized as those who underwent EVH (EVH group, n = 44) or open vein harvesting (OVH) (OVH group, n = 125). This method involves the creation of a small incision (2 cm), sufficient saphenous vein dissection near the skin incision, adequate dissection to separate the vein from the surrounding tissues, and the back-approach technique with C-ring to divide the side branch of the saphenous vein. The primary endpoint was the graft patency rate, and the secondary endpoints were leg wound complications and length of hospitalization.ResultsNo significant intergroup difference was observed in early patency of saphenous vein graft patency (OVH vs. EVH = 94.7 vs. 95.6%, p = 0.763). The incidence of lower extremity wound lymphorrhea was significantly lesser (OVH: EVH = 16.0: 0.0%, p = 0.005) and the length of hospitalization was also significantly shorter in the EVH group (OVH vs. EVH = 24.2 ± 9.8 vs. 19.0 ± 5.3 days, p = 0.001).ConclusionsEVH, using the back-approach technique, showed satisfactory short-term results; therefore, this technique performed with C-ring might be effective for vein harvesting during EVH.     

Reconstruction of ureteral defects with microvascular vein grafts in a rat model

This study was undertaken to test the performance of an autologous vein graft as a ureteral replacement in the rat model. Twenty-six rats were divided into three groups. In Group 1 (n = 10), the animals had a 3-mm segment of the ipsilateral ureter excised and the ureteral defect repaired, using a superficial epigastric vein graft. In Group 2 (n = 10), the same ureteral defect was created and again repaired, using a superficial epigastric vein graft, with the addition of a Silastic stent. The control, Group 3 (n = 6), had the ureter transected and repaired solely by means of primary anastomosis. Animals from each group underwent urography and were sacrificed for histology at three different postoperative intervals: 1, 4, and 12 weeks. Postoperative urography results showed normal renal function in the animals with ureteral reconstruction using vein grafting aided by a stent, as well as in those with primary ureteral anastomosis. No renal function return was seen in the animals with ureteral reconstruction by vein grafting alone, without stent support. Histologically, a progressive loss of the vascular endothelium, and replacement with the urothelium typical of the ureter, was seen in the stented vein grafts. Severe ureteral obstruction at the proximal site of the graft and hydronephrosis were seen in the vein-graft group without stenting. This study demonstrates that autologous vein grafts can be used successfully to correct a ureteral deficit, contingent on accurate microsurgical technique and immediate stenting.     

A modified method of microvascular autogenous interposition vein grafting for vascular reconstruction

A modified technique of vein grafting for vascular reconstruction that facilitates surgical procedures by preventing size, diameter, and length discrepancies as well as twisting, is presented. The distal end of the harvested vein graft is ligated, and the graft is inflated with heparinzed saline. The determination of the small side branches makes ligation easier. Gentle hydrostatic dilation relieves spasm, straightens the vein, and ligation of the proximal end is then performed under tension. As the vein inflated with heparinzed saline achieves maximum size, diameter, and length without torsion, the sausage-like graft can easily be interposed in tunnels, passages, or soft tissues between recipient vessel gaps. As the graft is under adequate tension, it is easy to determine its appropriate length, size, and diameter. Suturing is carried out using double approximating clamps. The graft will not twist or kink, as it is anastomosed under tension. The clamps are left in place until completion of the distal and proximal anastomoses. The distal clamp is released first. With this simple modification, most of the technical difficulties, such as length, size, and diameter discrepancies, and twisting and torsion of the graft, can be eliminated. The risk of failure due to vascular thrombosis at the anastomotic sites is lowered, as the vein graft is filled with heparinzed saline, and no blood flow is permitted during the reconstruction. The surgeon also saves time with this easy, simple, and feasible method.     

Permanent access to the portal vein in rats: an experimental model

A safe and reproducible method for placement of indwelling catheters into the portal venous system is a prerequisite for improved delivery of anticancer drugs to experimental liver metastases. Due to the lack of tumor models in large animals and the difficulty in establishing permanent access to the portal vein in rodents, this type of model has rarely been described in the laboratory setting. We propose a simple, minimally invasive method for repeated portal vein injections in rats. A vascular access device was used, which remained patent for periods of up to 3 months. Placement and support of the catheter tip in the portal vein was performed with a technique designed to avoid portal thrombosis and infections. Permanent portal vein access in a rodent model of liver metastases will be invaluable for the development of novel therapeutic strategies.     

The strength of microvascular anastomoses— an experimental evaluation in rats

To determine the longitudinal strength of microvascular anastomoses during early healing, the left femoral arteries of 56 rats were divided and anastomosed with six interrupted sutures of 10– 0 nylon. The right femoral arteries served as unoperated controls. The vessels were then harvested immediately, or 3, 7, 14, 21, 28, or 120– 150 days after surgery. The crosssectional surface area was measured and the force required to pull the vessels apart (burst strength) was determined with a tensiometer. Fifty- four of the 56 anastomosed vessels were patent at the time of harvest. All of the operated vessels ruptured at the site of anastomosis when the sutures pulled through the vessel wall. The mean burst strength of the anastomosed vessels was 44% of the contralateral unoperated controls immediately after surgery and did not significantly increase for four to five months. It was concluded that early mobilization of replanted parts is not limited by the strength of microarterial anastomoses.     

Autologous fat grafting: a technique for stabilization of the microvascular pedicle in DIEP flap reconstruction

Proper orientation of the microvascular pedicle is essential to ensure a high success rate in microvascular surgery. The inset of a deep inferior epigastric perforator (DIEP) flap breast reconstruction can sometimes be problematic given the long vascular pedicle, the acute takeoff from an internal mammary anastomosis, and the positioning of the flap on top of the vascular pedicle. In the postoperative period, the flap can also shift as the patient's activity level increases. We present a technique where nonvascularized autologous fat grafts are used to stabilize and cushion the vascular pedicle. Over a 14-month period, 117 consecutive DIEP flaps were performed to the internal mammary vessels with autologous fat grafting to the microvascular pedicle. Six flaps (5.1%) were explored during the immediate postoperative period for anastomotic compromise. Only one total flap failure (0.8%) was observed during this time. We had no direct complications related to the fat grafts. The use of nonvascularized autologous fat grafts is a simple and safe technique for stabilization of a microvascular pedicle. It should be considered in DIEP flap breast reconstruction and other microvascular cases where the vascular pedicle might be compressed by adjacent structures.     

Comparison of experimental microvascular end-to-end anastomosis via VCS-Clips versus conventional suture technique in an animal model

In this experimental study on 96 CD rats, microvascular end-to-end anastomoses created via suture or alternatively by means of a VCS-Clip-Application-System, were compared. The aorta abdominalis of the animals, with a diameter of 1.5 +/- 0.2 mm, was experimentally dissected, and the free ends of the vessel then anastomosed. The results were evaluated using sonography, microangiography, histologic examination, and vascular imprints. Postoperative examination was carried out after 1, 3, 7, 14, or 30 days. Major advantages of the VCS-Clip technique over suturing were that it was easy to learn, significantly faster to perform (execution of anastomosis 10.9 +/- 2.6 min versus 19.4 +/- 5.0 min), and produced significantly more favorable histologic results in terms of less inflammatory response, foreign body reaction, necrosis of the tunica media, hyperplasia of the intima, and thrombosis of the vessel lumen. The main disadvantage of the clip technique was a significantly higher rate of stenoses (15.8 +/- 6.0 versus 4.1 +/- 6.6 percent).