An experimental study of delay of flow-through venous flaps

Unconventional Perfusion Flaps in the Experimental Setting: A Systematic Review and Meta-Analysis

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Background:

Unconventional perfusion flaps offer multiple potential advantages compared with traditional flaps. Although there are numerous experimental articles on unconventional perfusion flaps, the multiple animal species involved, the myriad vascular constructions used, and the frequently conflicting data reported make synthesis of this information challenging. The main aim of this study was to perform a systematic review and meta-analysis of the literature on the experimental use of unconventional perfusion flaps, to identify the best experimental models proposed and to estimate their global survival rate.

Methods:

The authors performed a systematic review and meta-analysis of all articles written in English, French, Italian, Spanish, and Portuguese on the experimental use of unconventional perfusion flaps and indexed to PubMed from 1981 until February 1, 2017.

Results:

A total of 68 studies were found, corresponding to 86 optimized experimental models and 1073 unconventional perfusion flaps. The overall unconventional perfusion flap survival rate was 90.8 percent (95 percent CI, 86.9 to 93.6 percent; p < 0.001). The estimated proportion of experimental unconventional perfusion flaps presenting complete survival or nearly complete survival was 74.4 percent (95 percent CI, 62.1 to 83.7 percent; p < 0.001). The most commonly reported animal species in the literature were the rabbit (57.1 percent), the rat (26.4 percent), and the dog (14.3 percent). No significant differences were found in survival rates among these species, or among the diverse vascular patterns used.

Conclusion:

These data do not differ significantly from those reported regarding the use of unconventional perfusion flaps in human medicine, suggesting that rabbit, rat, and canine experimental unconventional perfusion flap models may adequately mimic the clinical application of unconventional perfusion flaps.

Revascularization of Arterialized Venous Flaps through a Total Retrograde Reverse Blood Flow: Randomized Experimental Trial of Viability

Background:

Arterialized venous flaps (AVFs) have been used for reconstruction of soft tissue defects throughout the body. Several different revascularization models have been performed, but venous drainage through the arterial system has not been studied. In our total retrograde reverse blood flow (TRRBF) perfusion model, the arterial blood flow enters through the venous system and venous drainage exits through the arterial system.

Methods:

We developed a novel experimental model in rabbit ears to evaluate the capacity of TRRBF perfusion pattern to allow AVF viability. The ears were assigned to 3 groups: group 1, total devascularization without revascularization (n = 3); group 2, TRRBF (n = 12); and group 3, conventional AVF (n = 12). The ears were observed during a 30-day follow-up period, and clinical serial assessment of edema, cyanosis, and necrosis was performed. Tissue oxygenation was determined at the beginning and end of the follow-up. Histological analysis was performed.

Results:

Necrosis was found in 3/3 (100%) ears in group 1, 3/12 (25%) in group 2, and 0/12 (0%) in group 3 (95% CI, 0.505–0.994; P = 0.0001). In group 2, edema was higher (5/12, 41.66%) than in group 3 (0/12, 0%) (95% CI, 0.0135–0.65; P = 0.041). Cyanosis and venous congestion was of greater intensity and duration in group 2 than in group 3 (10.33 ± 4.51 vs 4.5 ± 2.06 d).

Conclusions:

Although evolution is torpid and prolonged in ears with TRRBF, 9/12 (75%) survived, suggesting that TRRBF can be used as a rescue method.

Delay of the reverse pedicled venous island flap: clinical applications

In patients with hand or foot injuries, the delay procedure of the reverse pedicled venous flap was applied, including the loose areolar tissue around the pedicle vein. As preliminary clinical observations, five patients were treated with delay and the results compared with those of four patients without delay. The delay procedures were two types: type 1 was circumferential incision with ligature of the proximal vein, and type 2 was a bipedicled flap without ligature of the pedicle vein. Two weeks later, the flap was transferred to the defect. In the patients treated without delay, the maximum limit of the perfectly survived flap sizes was 4.0 × 2.0 cm. However, in the patients treated with delay, the perfectly survived sizes were 5.0 × 3.0 cm and 10 × 4.0 cm in type 1 delay and 12 × 5.0 cm in type 2 delay. The delay procedure appeared to stabilise the reverse pedicled venous flap and to expand its clinical applications.

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

OBJECT

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.

MATERIAL AND METHODS

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.

RESULTS

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).

CONCLUSION

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.

Reactive oxygen species in experimental ischemic flow-through venous flaps and effects of antioxidants on reactive oxygen species and flap survival

We made an experimental study on rabbit ears using an ischemic flow-through venous flap model to determine the changes in levels of reactive oxygen species (ROS) in venous flaps and effects of exogenous antioxidants on endogenous antioxidant superoxide dismutase (SOD) and ROS indicator malonyldialdehyde (MDA) levels and on flap survival. Mean SOD level significantly decreased and the MDA level significantly increased after the flap elevation according to basal levels of untreated flaps. The mean flap survival rates in the exogenous SOD or glutathione (GSH)-treated groups were significantly increased with respect to the untreated group. The SOD level was increased significantly and the MDA level was decreased significantly in the SOD- or GSH-treated groups relative to the control group after the flap elevation. These results have suggested that ROS may have an important role in ischemic flow-through venous flap pathogenesis and additionally, antioxidants could enhance the rate of flap survival.

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.