Direct monitoring of the microcirculation in experimental venous flaps with afferent arteriovenous fistulas

Treatment of Patients With Electrical Injury by Using Modified Forearm Venous Flap: Retrospective Case Series Study

OBJECTIVE

Severe hand electrical injuries often occur in functional areas such as joints; the repair requires attention to both appearance and function due to the visibility of the hand. This study aimed to present the clinical experience of successfully repairing hand electrical injuries using improved forearm venous flaps.

METHODS

From 2020 to 2022, 15 cases of severe hand electrical injuries were diagnosed, including 10 males and 5 females. Among them, 6 cases were repaired in the first web space, 4 in the thumb, 3 in the index finger, 2 in the middle finger, 2 in the ring finger, and 2 in the little finger. The size of venous flaps ranged from 2.0 cm × 1.8 cm to 12 cm × 4.0 cm. All patients underwent repair using improved forearm venous flaps. The follow-up period ranged from 5 to 8 months.

RESULTS

All flaps survived without serious complications. All patients were satisfied with the postoperative aesthetics and function of their hands.

CONCLUSION

The improved forearm venous flap is a simple and reliable method for repairing hand electrical injuries.

Conditioning of microvascular venous flaps in rats

Venous-only perfusion flaps have not been used widely because of the associated high failure rate. Tissue conditioning offers a broad scope of techniques that can be applied pre-, peri-, or postoperatively to promote the adaptation of the affected tissue to any subsequent stress. This study aimed to assess the survival rates associated with a pure venous perfusion flap and investigate whether the timing of the vascular conditioning can affect free flap survival. Forty-four rats were included in the experiment. Group I underwent veno-arterial anastomoses with epigastric graft with pure venous perfusion without tissue conditioning. Groups II and III were pretreated for 7 or 14 days with ischemic conditioning. These groups were compared with a control group (group IV) of conventionally perfused flaps. After the initial surgery, all flaps were assessed clinically, photometrically, and by indocyanine green videoangiography. The flap success rates were 0% in group I, 49.97% ± 24.34% in group II, and 64.95% ± 20.36% in group III. The control group showed an overall survival of 89.3% ± 6.51%. With suitable conditioning, pure venous blood supply can provide adequate perfusion in the rat epigastric flap model. The timing of vascular conditioning appears to be critical for flap survival.

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.

Free medialis pedis venous flap transfer for reconstruction of volar finger defects: Clinical application and esthetic evaluation

BACKGROUND

There have been many reports about venous flaps, which are often used for the reconstruction of soft tissue defects after finger injury because such flaps are simple to elevate. Recently, high viability rates and nearly normal histological findings were reported for venous flaps, although the mechanism of flap survival remains unclear. This study investigated the esthetic outcomes after the reconstruction of volar finger defects with free medialis pedis venous flaps, which are venous flaps that elevated between the submalleolar and medial plantar regions.

MATERIALS AND METHODS

Reconstruction of volar finger defects was performed in 6 patients. All flaps were arterialized flow-through flaps with the venous anastomosis as the outflow. All 6 patients were men, with a mean age of 32.0 years. The defect involved the finger shaft in 4 patients and the finger pulp in 2 patients, and the mean size of the venous flap was 16.7 mm (width) × 34.2 mm (length). Five plastic surgeons specializing in maxillofacial surgery evaluated the color match of the flaps at 6 months postoperatively by assigning a score (maximum: 5 points).

RESULTS

The flap showed complete viability with little postoperative atrophy in all 6 patients. The mean color match score for the flaps was 3.7, and it decreased as the flaps were raised further from the medial plantar region.

CONCLUSION

Free medialis pedis venous flaps can be used for the reconstruction of volar soft tissue defects of the finger. Acceptable esthetic results can be obtained if flaps are harvested from an appropriate location in the medialis pedis region by a suitable method.

The position of 'shunt restriction' along an arterialized vein affects venous congestion and flap perfusion of an arterialized venous flap

Restriction of arteriovenous (AV) shunting has been shown to enhance peripheral perfusion and also reduce venous congestion of an arterialized venous flap. Thus, this study is designed to investigate the effect of 'shunt-restriction' location on venous congestion and flap perfusion in a 'shunt-restricted' arterialized venous flap (AVF).

METHODS

Abdominal flaps based on the thoracoepigastric vessels of Sprague-Dawley rats were raised. The inferior epigastric vein was repaired to the femoral artery in order to create an AVF. The superior epigastric vein was preserved for drainage. Microcirculation and laser Doppler flowmetry results were compared between AVFs with 'shunt restriction' at a proximal third (SR-proximal) distance and 'shunt restriction' at a distal third (SR-distal) distance.

RESULTS

Bidirectional sluggish flow was detected at the proximal part of venous flaps in both groups. Unidirectional normal flow was observed in more capillaries of the distal flaps in the SR-proximal group. In the middle of the flaps, blood flow was sluggish and intermittent in the veins and was absent in most capillaries of the SR-distal group. The flow was prompt and unidirectional in more capillaries of the SR-proximal group. Using laser Doppler flowmetry, the average perfusion of the whole SR-proximal flaps was found to be higher than that of SR-distal flaps (p = 0.017). The average flux at the middle and distal portions of the SR-proximal group was significantly higher than those of the SR-distal group (p = 0.049).

CONCLUSION

'Shunt restriction' at the proximal third of the AV shunt resulted in enhanced perfusion and reduced venous congestion in an AVF.

Arterialized venous flow-through flaps in the reconstruction of digital defects: case series and review of the literature

BACKGROUND

Arterialized venous flow-through (AVFT) flaps are useful in reconstructing small soft tissue defects. Currently, no guidelines exist for the use of AVFT flaps for reconstructing soft tissue defects in the digits of the hand. We retrospectively reviewed our experience with AVFT flaps and developed a selection process for vascular anastomoses.

METHODS

We reviewed the use of AVFT flaps in a series of ten consecutive patients requiring reconstruction of small soft tissue defects of the fingers.

RESULTS

Between 2006 and 2012, ten consecutive digital reconstructions were performed using AVFT flaps. Flap sizes ranged from 5 to 13.5 cm(2). Initial congestion was seen in all flaps and resolved within 3-7 days. Leeches were utilized in two cases. All cases achieved good functional results. Three illustrative cases from our series of ten are presented, each demonstrating key decision-making factors in selecting recipient and flap vessels for anastomosis.

CONCLUSIONS

AVFT flaps appear congested post-operatively, resolving in days to weeks, and resulting in healthy coverage of digital soft tissue defects with good functionality. We suggest a selection process for the use of AVFT flaps in digital soft tissue reconstruction, based on dorsal vs. volar and proximal vs. distal defect location, and the flap's inherent venous architecture.

The effect of hemodynamic remodeling on the survival of arterialized venous flaps

Objective

To evaluate the effect of hemodynamic remodeling on the survival status of the arterialized venous flaps (AVFs) and investigate the mechanism of this procedure.

Materials and Methods

Two 7 x 9 cm skin flaps in each rabbit (n=36) were designed symmetrically in the abdomen. The thoracoepigastric pedicle and one femoral artery were used as vascular sources. Four groups were included: Composite skin grafts group and arterial perfusion group were designed in one rabbit; AVF group and hemodynamic remodeling group by ligation of the thoracoepigastric vein in the middle were outlined in another rabbit. Flap viability, status of vascular perfusion and microvasculature, levels of epidermal metabolite and water content in each group were assessed.

Results

Highly congested veins and simple trunk veins were found using angiography in the AVF group; while a fairly uniform staining and plenty of small vessels were observed in the hemodynamic remodeling group. The metabolite levels of the remodeling group are comparable with those in the arterial perfusion group. There was no statistically significant difference in the percentage of flap survival between the arterial perfusion group and hemodynamic remodeling group; however, significant difference was seen between the AVF group and the hemodynamic remodeling group.

Conclusions

Under the integrated perfusion mode, the AVFs are in an over-perfusion and non-physiological hemodynamic state, resulting in unreliability and unpredictability in flap survival; under the separated perfusion mode produced by remodeling, a physiological-like circulation will be created and therefore, better flap survival can be expected.

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.

Free arterialised flow-through venous flap with venous anastomosis as the outflow (A-A-V flap) for reconstruction after severe finger injuries

Abstract For reconstruction of volar defects, an arterialised flow-through venous flap (A-A flap) can be used to restore the soft tissues and the digital artery at the same time. However, there have been reports that the circulation of this flap is inadequate. This study used a venous flap with only one venous anastomosis for the outflow of an A-A flap (A-A-V flap) to solve this problem. Six patients with defects of the finger soft tissues and digital artery after severe finger injuries were performed. The venous flap with a Y-shaped vein was harvested. The digital artery was reconstructed, after which the other proximal vein of this flap was anastomosed to the dorsal subcutaneous vein. The flap survived in all patients and histological examination of flap tissue showed a nearly normal architecture. This study describes the good results obtained with an A-A-V flap, and discusses the utility of our flap in comparison with previously reported venous flaps.

The physiology, microcirculation and clinical application of the shunt-restricted arterialized venous flaps for the reconstruction of digital defects

Reconstruction of digital defects using the venous flap offer several advantages but remained unpopular owing to levels of venous congestion rates. We performed animal studies to test the hypothesis that an arterio-venous shunt increases pressure for peripheral flap perfusion and decreases venous congestion. Using an abdominal adipofascial flap model in six male Sprague-Dawley rats, microcirculation was modified as follows: type I - arterial flap; type II - flow-through arterio-venous flap (AVF); and type III - shunt-restricted AVF. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type II flaps, blood flow oscillated without a dominant direction and came to a standstill. In type III flaps, blood flowed proximally in a reverse direction whereas distally, flow was similar to type I flaps. In a clinical series, 21 patients received a total of 22 shunt-restricted AVFs. All 22 clinical flaps survived; four flaps suffered epidermolysis but recovered without full thickness loss.

Replantation of a degloved hand with added arteriovenous anastomoses: report of two cases

Revascularization of the degloved skin is generally accepted as the best option for the management of totally degloved hands. Nevertheless, the selection of vessels for anastomoses is usually difficult in this situation, and insufficient perfusion of the degloved hand skin is common after arterial repair. We present 2 cases of patients who sustained totally degloved hand injuries. Favorable outcomes of replantation were achieved with added arteriovenous anastomoses between the dorsal veins of the degloved hand skin and the digital arteries.

Microcirculation Study of Rabbit Ear Arterial and Venous Flow-Through Flaps Using a Window Chamber Model

Venous flaps are used widely for finger reconstruction because they provide thin tissue, and the flap harvest is associated with less donor-site morbidity. The viability of the venous flap, however, is not as good as that of the ordinary perfused skin flap, and its microcirculation is questionable according to various indirect observations and hypotheses in the literature. Using a window chamber model in a rabbit ear, both arterial and venous flow-through flaps were studied. Factors evaluated were flap viability, flap weight, flap circulation as assessed by laser Doppler flowmetry, and direct observation of the microcirculation. Statistical analysis was performed using the two-sample t test. There was no statistically significant difference in viability between arterial and venous flow-through flaps (p = 0.661). The arterial flow-through flap had better perfusion than thevenous flow-through flap, as measured by laser Doppler perfusion studies (10.40 perfusion units [PU] vs 4.50 PU). However, no statistically significant difference was noted (p = 0.0717). Flap weight assesseed 1 week after surgery and oxygen saturation measured immediately after surgery showed significant differences between the arterial and venous flow-through flaps (p = 0.0001 and 0.0279). These datasuggest that the arterial flow-through flap is subjected to more congestion becauseof the abnormal flow pattern seen, andpossibly because of a superior inflow or nutritional status found in these flaps. Using vital microscopy, direct evaluation of the microcirculation was performed. A to-and-fro phenomenon was noted in both arterial and venous flow-through flaps,which was followed by a reversed direction of flow in part of the microvasculature. With both types of flaps, the blood was directed eventually from the postcapillary venules to the capillaries, through the terminal arterioles, and then to the arterioles. These findings may be explained partially by the normal physiologic pressure gradients present in the microvasculature of these flaps. In this study, direct observation of the microcirculation was used as well as other objective measures to determine the flow patterns and clinical behaviors found in these types of flaps. A model in a rabbit ear for the study of venous and arterial flow-through flaps is described, and clinical correlations are 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.