Survival Of Venous Flaps Research Articles

Effect of hirudin on arterialized venous flap survival in rabbits

Arterialized venous flap (AVF) is limited in clinical application because its survival remains inconsistent and its exact survival mechanism is still unclear. Hirudin is an effective thrombin specific inhibitor, which is isolated from the salivary gland secretions of the leech. Our study evaluated the impact of hirudin on the viability of AVFs in rabbits. Thirty-six rabbits were randomly divided into three groups: sham group (physiological perfusion), control group (AVF), and hirudin group (AVF + hirudin). In hirudin group, 20 antithrombin units (ATU) hirudin (2.5 ml) were injected into each flap. In sham group and control group, the same amount of normal saline was injected into each flap. Status of flap survival, water content, vascular perfusion, histopathology, expression of CD34, VEGF, eNOS and HIF-1α were analyzed in each group. Analysis of oxidative stress was performed by measuring the activity of superoxide dismutase (SOD) and malondialdehyde (MDA). Compared with flaps in sham group with physiological perfusion mode, results of survival rate, perfusion status, SOD activity, expression of CD34, VEGF, and eNOS of AVFs in control group were significantly lower, while water content, MDA level and expression of HIF-1α were higher. The flap condition of AVFs injected with hirudin in hirudin group was improved significantly, and the results were similar to sham group. Our findings revealed that hirudin can effectively improve survival of AVF.

Venous Flaps for Revascularization and Soft-Tissue Coverage in Traumatic Hand Injuries: A Systematic Review of the Literature.

The use of the venous flap for simultaneous revascularization and coverage of soft tissue defects has been documented in the literature for over 30 years. First described in 1981, Nakayama et al demonstrated that a vein and overlying skin, or a venous flap, may be transposed from one area of the body to another with complete survival of the graft. The aim of this study was to conduct a systematic review of the literature to determine predictors of venous flap survival in traumatic hand injuries. A literature search of PubMed, MEDLINE, and Cochrane Library was performed with emphasis on venous flap use in traumatic hand injuries. MeSH terms included: vein graft, revascularization, venous flow through flap, arterialized venous flap, bypass, replantation, amputation, avulsion, trauma, injury, amputate, finger, hand, and thumb. Forty-three articles were collected that contained data on 626 free venous flaps. Most patients were males (73.9) and injured their right hand (52.3%). The forearm was the most commonly used venous flap donor site (83.6%), and most of the skin paddles were 10 to 25 cm2 (41.1%). Arterial inflow was used in 93.1% of the flaps. Most venous flaps (79.6%) healed without superficial tissue loss or necrosis. Ninety-two (14.7%) flaps had partial loss while 36 (5.8%) flaps did not survive. The use of venous flaps for concomitant revascularization and soft tissue coverage of the hand permits good results with limited morbidity. The overall flap survival rate is nearly 95%. Younger patients whose flaps have arterial inflow and skin paddles of medium size (10-25 cm2) have the best chance for survival.

Allogenic endothelial progenitor cell transplantation increases flap survival through an upregulation of eNOs and VEGF on venous flap survival in rabbits

Endothelial progenitor cells (EPCs) are one type of bone marrow hematopoietic stromal cells which play a vital role in neovascularization and tissue repair. In this study, we investigated whether EPCs promote flap survival in a rabbit venous model. EPCs were customized from CHI Scientific, Inc, China. Thirty-six rabbits were randomly assigned to either the sham group (n = 12), the control group (n = 12) or the EPC transplantation group (n = 12). A 10 × 6cm venous flap was created on the rabbit abdomen. Both the EPC transplantation and control groups had the same volume of EPCs-PBS (phosphate buffered saline) and PBS on postoperative day 1. Flap survival, blood flow, histopathology, expression of endothelial nitric oxide synthase (eNOs) and Vascular Endothelial Growth Factor (VEGF) were detected on postoperative day 10. Cellular immunofluorescence assay positively confirmed that the EPCs were undergoing differentiation. The survival rate of the flap in the EPC transplantation group was 58.4±7.1%, which was significantly higher than that of the control group (4.8±3.4%) (p<0.01). Histological examination revealed that the EPC transplantation group had higher microvessel density, fewer inflammatory cells, and a higher expression of eNOs and VEGF. Significantly increased blood flow perfusion was seen in the EPC transplantation group using laser Doppler imaging. The Western Blot technique revealed that the expression of eNOs and VEGF in the EPC transplantation group were both significantly higher than those in the control group. This study demonstrated that EPC transplantation improved venous flap survival in rabbits. The present findings may provide insight into the promotion of venous flap survival in clinical practice in the future.

A single center comparison of one versus two venous anastomoses in 564 consecutive DIEP flaps: investigating the effect on venous congestion and flap survival

A single center comparison of one versus two venous anastomoses in 564 consecutive DIEP flaps: investigating the effect on venous congestion and flap survival

Improvement of Prearterialized Venous Flap Survival with Delay Procedure in Rats

The purpose of this experimental study is to investigate the improvement in flap survival of prearterialization with delay procedure in venous flaps in rats. The transverse superficial inferior epigastric flap was utilized. Forty-six rats were randomized into four groups: group 1 as arterialized venous flaps, group 2 as venous flaps of prearterialization with delay procedure, group 3 as arterial perfusion venous flap, and group 4 as venous perfusion venous flap. Direct observation, histological analysis, and vascular perfusion examination by Indian ink injection were performed for flap assessment. The percentage of flap survival was 41.6 +/- 2.4%, 98.0 +/- 1.8%, 89.5 +/- 1.0%, and 11.3 +/- 0.8% in these four groups, respectively. Significant differences were noted between groups ( P < 0.05) except for between group 2 and group 3 ( P > 0.05). Vascular perfusion studies revealed that the Indian ink filled the entire flaps of group 2 in comparison with partially filled flaps in other groups. Histological examination showed more small vessels were observed through all layers of the flaps as well as dilated superficial veins in group 2 than those in other groups. In conclusion, prearterialization with delay procedure can improve the viability of the flap, and this method may be a strategy for flap prefabrication based on the venous network.

Nitric Oxide in Flow-Through Venous Flaps and Effects of l-Arginine and Nitro-l-Arginine Methyl Ester (l-NAME) on Nitric Oxide and Flap Survival in Rabbits

Venous flaps are relatively recent practices in plastic surgery, and their life mechanisms are not known exactly. Partial necroses frequently occur in these flaps; therefore, their survival should be enhanced. Nitric oxide (NO) is an endogenous compound which has recently been dwelt upon frequently in flap pathophysiology, and its effect on viability in conventional flaps has been demonstrated. However, its role in venous flaps is unknown. The purpose of this study is to determine possible changes in the NO level in venous flaps and to investigate the possible effects of NO synthesis precursor and inhibitor on the venous flap NO level and flap survival. Thirty white male rabbits of New Zealand type, aged 6 months, were divided into 3 groups as control (n = 10), L-arginine (n = 10), and nitro-L-arginine methyl ester (L-NAME) (n = 10). Blood and tissue samples were taken from one ear of 10 rabbits in the control group for the determination of NO basal levels 2 weeks before flap practice. The 3-x-5-cm flow-through venous flaps, which are sitting on the anterior branch of the central vein, were elevated on each ear of 10 rabbits in all groups. After flaps were sutured to their beds, 2 mL/d saline, 1 g/kg/d L-arginine (NO synthesis precursor), and 50 mg/kg/d L-NAME (NO synthesis inhibitor) were administered intraperitoneally in control, L-arginine, and L-NAME groups, respectively, for 3 days. At the 24th postoperative hour, blood and tissue samples were taken from all animals for biochemical analyses. At day 7, flap survivals were assessed. Mean NO levels in the blood following the flap elevation (129 +/- 76 micromol/mg protein) increased in comparison with basal levels (59 +/- 44 micromol/mg protein) (P < 0.06); however, the tissue level remained unchanged. NO levels in the blood in the L-arginine and L-NAME groups were alike compared with the control group. The tissue NO level in L-NAME group (0.08 +/- 0.03 micromol/mg protein) decreased significantly compared to the control group (0.46 +/- 0.36 micromol/mg protein) (P < 0.001). Mean flap survival in the L-arginine group (95% +/- 6) increased according to the control group (61% +/- 14) (P < 0.001), whereas it did not change in the L-NAME group (55% +/- 13). In our model of venous flap, NO level in the blood increased, while it did not change in the tissue; L-arginine significantly enhanced flap viability without affecting NO level. Additionally, L-NAME decreased NO level, but it did not affect flap survival. In light of these findings, NO increases in venous flaps; the change in its level does not affect flap survival, though. However, L-arginine enhances venous flap survival if not by virtue of NO.

Improvement of Venous Flap Survival by Application of Vascular Endothelial Growth Factor in a Rat Model

Expression of vascular endothelial growth factor (VEGF) in the venous flap and the effect of exogenous VEGF on survival of the venous flap were studied in rats. A 4- x 4-cm groin type 2 venous skin flap was used in the study. In part 1, biopsies were taken from the flap at 0, 6, 12, 24, and 48 hours after the flaps were raised. VEGF gene expression was measured. In part 2, exogenous VEGF (1 microg/mL) was injected subdermally into the flaps in 10 rats before the flaps were replaced. Flaps that received a saline injection were used as the control. Skin paddle survival was measured on postoperative day 7. The results showed that VEGF expression was significantly increased at 24 and 48 hours after venous flap elevation (P < 0.05). Injection of exogenous VEGF to the flap significantly improved survival of the flap (73% of the flap) when compared with the control, which had a 39% mean percent survival (P < 0.05). We conclude that VEGF expression was increased in the venous flap. Administration of exogenous VEGF significantly improved survival of the venous flap.

Effects of methylprednisolone on the viability of experimental flow-through venous flaps.

In this study, the effects of a corticosteroid, methylprednisolone, on the survival of flow-through venous flaps were investigated in rabbits. Flow-through venous flaps, sized 3.0 x 4.5 cm, were raised in the rabbit-ear model. Animals were randomly distributed into three groups, and 30 flaps were raised as follows: Group 1 (n=10): control flow-through venous flaps (intramuscular saline injection 2 ml/d); Group 2 (n=10): flow-through venous flaps with daily intramuscular methylprednisolone injection (30 mg/kg/d); and Group 3 (n=10): negative control composite grafts with the flow-through vein ligated at both edges of the flap. All injections were done 24 hr and 1 hr preoperatively, and for 5 days postoperatively. Observations included gross and histologic examination, and percentage of survival of the flaps on the tenth day. Venous flaps of the animals receiving daily methylprednisolone injections (Group 2) were noted to have statistically significantly improved flap survival ( p<0.05), compared to the control group (Group 1). Flaps in Groups 1 and 2 demonstrated significantly higher survival rates, compared to the composite grafts ( p<0.01). Histologic examination of methylprednisolone-treated animals showed normal stratified squamous epithelium, while complete necrosis was noted in the composite grafts. Untreated flow-through venous flaps demonstrated patchy epidermal sloughing, crusting, and partial necrosis. These results suggest that the survival of potentially ischemic flow-through venous flaps can be enhanced in rabbits by daily methylprednisolone treatment in the perioperative period. Increased tolerance to ischemia and modulation of venous flap microcirculation might be possible mechanisms for this salutary effect.

The effect of pentoxifylline on venous flap survival

An experimental study was performed to determine whether the survival area of a flap can be increased using pentoxifylline in a single-pedicled venous skin flap in the rat. Epigastric island venous skin flaps measuring 1.5×2.5 cm were constructed bilaterally. The experimental group received intraperitoneal injections of pentoxifylline 25 mg/kg daily for 7 days following the operation. This study shows the pentoxifylline had no beneficial effect on single-pedicled venous island skin flap viability in the rat model.

Effects of some pharmacological agents on the survival of unipedicled venous flaps: an experimental study.

Clinical and experimental studies have been conducted to improve the survival of venous flaps. As a result of these studies, although various survival mechanisms were raised, none obtained satisfactory information. Venous stasis, and the resultant venous thrombosis, is a factor that decreases the survival of venous flaps. In this study, we evaluated the effects of two antiinflammatory agents, etodolac and etofenamate, on the survival of unipedicled venous flaps. In this study, 35 male New Zealand white rabbits (3,500-4,000 g) (70 ears) were used. Perichondrocutaneous flaps, 3 x 4.5 cm in size, were designed and raised, keeping the central veins intact in the middle of venous flap. Central arteries and nerves were ligated and transected both proximally and distally, to prepare unipedicled venous flaps. A silicone sheet was placed between the cartilage tissue and flap, to prevent blood flow and revascularization beneath. The subjects were divided into seven groups, consisting of five rabbits (10 ears). In the negative control group (group I), the single vascular pedicle of venous flaps, central veins were ligated and flaps sutured into their own place as the composite graft. In the positive control group (group II), after venous flaps were prepared, normal saline, 0.2 mL, was given subcutaneously. In the first of five experimental groups (group III), unfractionated heparin (100 U/day) was given subcutaneously. In the second experimental group (group IV), etodolac (5 mg/kg/day) was given subcutaneously. In the third experimental group (group V), etophenamate (5 mg/kg/day) was given orally through a feeding tube. In the fourth experimental group (group VI), parnaparin (5 anti-Xa U/kg/day) was given subcutaneously. In the fifth experimental group (group VII), nadroparin (5 anti-Xa U/kg/day) was given subcutaneously, about 7 days postoperatively. At the eighth postoperative day, surviving areas of venous flaps were measured, and the results were evaluated by Kruskal-Wallis ANOVA and Mann-Whitney U-test (P < 0.05). Biopsies were also taken from the flaps for histological evaluation of border of necrotic tissue. Surviving areas of unipedicled venous flaps were larger in experimental groups than those in negative and positive control group (P < 0.05). However, comparison of the experimental groups demonstrated no statistically significant difference (P > 0.05). We concluded that all pharmacological agents used in the experimental groups succeeded in increasing the survival of unipedicled venous flaps. Survival of the unipedicled venous flap was higher in venous flaps than that of composite graft, clearly showing the importance of the venous pedicle.

A microneurovascular study of the great saphenous vein in man and the possible implications for survival of venous flaps

Cross sections (n = 372) of human long saphenous veins (n = 12) from unsalvageable fresh above knee amputation specimens brought to a trauma centre in a large metropolitan hospital were studied. The veins were harvested longitudinally with an amount of soft tissue equivalent to the diameter of the vein and sectioned at intervals of 5 mm. The sections were stained with haematoxylin and eosin for general study, Van Gieson for better delineation of different coats of the vessel wall and reticulin stain to differentiate between venules and arterioles. The vascular structures within the vein wall and its surrounds were analysed by using analySISpro via a CCD camera attached to a light microscope, with the help of a frame grabber card and image analysis software. Results show that the vein has vasa vasorum within its wall, a capillary network around it, arterioles, venules and the saphenous nerve and its branches with their vascular network a further distance apart. The relevance of the microsurgical anatomy of the saphenous vein and its soft tissue envelope in the survival of venous flaps is discussed.

Comparison of two types of arterialized venous forearm flaps for oral reconstruction and proposal of a reliable procedure

The mechanism of survival of venous flaps is not yet completely understood. To determine the conditions for reliable success, in 1996 and 1997 we used arterialized venous forearm flaps for oral reconstruction in patients with neoplastic disease. Building on earlier experience with flow-through flaps, we compared two different designs obeying the following specifications: five so-called arterialized flow-through flaps, elevated from the ulnar flexor side of the forearm, with a single vein for orthograde inflow and outflow, diameter not larger than 2 mm (type 1); and five arterialized flaps with two parallel veins on the proximal side of the flap, also with a diameter of 1-2 mm, to avoid by-passing of flap tissue by 'catching' the blood in the venous/capillary system (type 2). There were nine male and one female patients with a mean age of 55.7 years. We covered defects of the anterior or anterolateral floor of the mouth to avoid folding of the flaps. Microsurgical anastomosis was done to the facial artery, the cranial thyroid artery and the external jugular vein or the facial vein. Average size of the flaps was 23 +/- 7.28 cm2 (type 1) and 25 +/- 5 cm2 (type 2). Four flaps of type 1 showed total or subtotal success and only one was lost because of a haematoma. In comparison with this we saw three losses in type 2 and only one partial and one total success, respectively. Analysis showed regularly occurring problems: there was failure of venous drainage in the lost type 2 flaps one day after microsurgery. In the flow-through flaps and the surviving type 2 flaps which had visible communicating branches between the two veins, the partial by-passing of the arterial input avoided this problem. There was no donor site morbidity after covering with a split-thickness skin graft. It could be shown that survival of arterialized venous forearm flaps is based on a combination of an arteriovenous shunt and capillary blood flow. In conclusion, we define six rules for a reliable venous forearm flap.

Expansion of venous flaps: an experimental study in rats

In this study, the effects of controlled tissue expansion on the survival of unipedicled venous flaps were investigated in rats. In three groups of Lewis rats, a 3 x 6 cm unipedicled Lateral thoracic venous flap was studied with group 1 as control group (n = 30) without any manipulation, group 2 (n = 30) where an expander was introduced under the flap area but was not expanded and group 3 (n = 30) in which a 40 ml expander was introduced under the flap area and was expanded over a period of 10 days. Observations included gross and histological examination, reverse microangiography, reverse flow resistance and percentage of survival of flaps. Group 3 (expanded) showed more angiogenesis, a better delineation on microangiography, lower reverse flow resistance and higher survival rates as compared to group 2 (non-expanded). In the control group the survival rate of flaps was the poorest and the flaps showed higher rates of reverse flow resistance. Microangiography was not successful in the control group. In a pilot project prior to this experiment microscopic examination of the Lateral thoracic vein in 10 Lewis rats had confirmed the presence of two or three valves in this vein.

Experimental study of mechanism of survival of venous flaps. (Chinese)

Experimental study of mechanism of survival of venous flaps. (Chinese)

The effect of glutathione, superoxide dismutase and adenosine triphosphate on venous flap survival

Oxygen-derived free radicals and the energy supply for resynthesis are important factors that affect flap survival. An experimental rabbit model was designed to investigate the effects of the free radical scavengers, glutathione (GSH), superoxide dismutase (SOD), and adenosine triphosphate (ATP-MgCL2), on venous flap survival. Four 4×6 cm flaps were elevated in each animal along the axis of the thoraco-epigastric veins. Postoperatively, the agents were administered intravenously and relative flap survival was measured after two weeks. Mean flap survival, using the free radical scavengers, ranged between 76 and 87%, which showed a significant improvement over saline controls (68.73%, p<0.01). The respective mechanisms of the individual agents are discussed.

The microcirculation and survival of experimental flow-through venous flaps

The subject of venous flaps is controversial. The purpose of this study was to investigate the haemodynamic changes and the survival process of venous flow-through flaps. Venous flaps and composite grafts were elevated along the axis of the thoracoepigastric veins in rabbits. The microcirculation was studied by capillaroscopy and injection studies. For the first 72 h, the flaps were nourished by venous blood; venous blood flowed slowly from the principal vein to its tributary veins and then through venous anastomoses to reach other tributary veins. No backflow from venules into capillaries was seen. New vessels began to grow into the flaps from 72 h postoperatively. Four days postoperatively, arterial flow with low velocity was seen in the primary flap arteries and the backflow of venous blood disappeared. Seven days postoperatively, the abnormal flow in “unphysiological” channels was replaced by normal flow in “physiological” channels. Six weeks postoperatively, the vessel structure of venous flaps was the same as that of normal skin. These results suggest that the profuse venous network in venous flaps and early invasion of new blood vessels are the mainstays of venous flap survival.

The pedicled venous flap. Clinical applications

Experimental findings of survival of pedicled venous flaps were clinically applied in seven cases for traumatic skin defects on digits. Five flaps which were transferred to or on digits other than the thumb survived, but two flaps from the index to the thumb developed partial necrosis. In order to prevent flap necrosis, the draining vein should be short.

The pedicled venous flap. An experimental study

Musculocutaneous pedicled venous flaps on the dorsum of rats survived at a statistically significantly higher rate than musculocutaneous composite grafts (p<0.01). With a Silastic ® sheet (Dow Corning) beneath, both composite grafts and pedicled venous flaps necrosed. When a Silastic ® sheet with holes in it to allow some revascularisation from the bed was placed beneath, the survival rate was significantly better than with a complete Silastic ® sheet (p<0.01). These results demonstrate that pedicled venous flap survival depends both on the draining vein, and revascularisation from the underlying bed.

An experimental study of the flow-through venous flap: investigation of the width and area of survival with one flow-through vein preserved.

A quantitative analysis was undertaken to investigate the width and area of survival of flow-through venous flaps in 20 ears of 10 rabbits. The 3.0- x 3.0-cm flap models, which included one flow-through vein, were prepared with additional circulation from the graft bed and surrounding tissue excluded, as far as possible. The flaps were divided as follows: Group A--composite grafts (n = 10), and Group B--flow-through venous flaps (n = 10). All flaps in Group A became necrotic and all those in Group B showed partial survival along the flow-through vein. The average survival width was 1.10 +/- 0.48 cm, and the survival rate was 44 +/- 19.3 percent. Microangiograms revealed patency of the flow-through vein in all flaps of Group B. Histologically, there tended to be progressively more fibrous tissue in the area further away from the flow-through vein. The model is useful to investigate the width and area of survival in flow-through venous flaps.

Biochemical analysis of the venous flap in the dog.

There has been great interest stimulated by reports on factors influencing the survival of skin flaps which possess only venous inflow and outflow, i.e., venous flaps. The present study serially (Days 1, 2, and 4 postoperatively) observed several biochemical factors which might affect flap survival. ATP levels were measured to assess endogenous energy stores, malonyldialdehyde (MDA) and xanthine oxidase (XO) to estimate free radical production, superoxide dismutase (SOD) to quantify antioxidant defenses, and edema to measure inflammatory changes. Eighteen thighs on nine dogs were assigned randomly to one of three groups: full-thickness skin grafts, flaps based solely on the saphenous artery and vein (AV flaps), or flaps based solely on the saphenous vein (venous flaps). These were regarded as being mostly ischemic, totally perfused, and partially ischemic, respectively. Control skin biopsies were obtained adjacent to surgical sites. AV flaps and control skin were similar in all respects. Venous flaps compared with skin grafts were significantly less edematous (P less than 0.01) had less MDA and XO (P less than 0.05), but no significant differences in SOD and ATP levels. However venous flaps had significantly less ATP than AV flaps (P less than 0.01). Thus venous flaps survive despite depletion of ATP levels. These results suggest that decreased free radical production and lessened edema may be important factors in promoting ultimate survival of venous flaps.