The effects of calcium channel blockers on random skin flap survival in the pig model

Summary This study was designed to evaluate the influence of two calcium channel blockers, verapamil and nifedipine, on skin flap survival. These agents were selected because they inhibit the passage of calcium through calcium selective channels in the plasma membrane, thereby blocking calcium mediated electromechanical coupling in contractile tissue and resulting in peripheral arterial vasodilation. Three groups of pigs were used in this study. All skin flaps in this study were 3 cm wide and 12 cm long. The first group (10 flaps) served as controls with no pharmacologic manipulations. Pigs in group II (15 flaps) received verapamil (80 mg orally, three times a day) for 7 days postoperatively. Pigs in group III (15 flaps) received nifedipine (10 mg orally, three times a day) for 7 days postoperatively. Statistical analysis of the results demonstrated that both verapamil and nifedipine resulted in significant enhancement of skin flap survival. The increased survival of the skin flaps produced by nifedipine as compared to verapamil was statistically significant.This study is supported in part by PHS Research Grant DE00853 from the National Institute of Dental Research     

Effect of aspirin on random pattern flap survival in rats

Aspirin is known to increase dermal perfusion and is commonly used to enhance anastomotic patency in microvascular surgery. However, we were unable to find any reports of an effect of aspirin on simple flap survival. In order to determine its effect on flap survival, a controlled experiment was designed using random pattern flaps in rats. The results indicate a statistically significant increase in flap survival in rats receiving aspirin. It is suggested that aspirin’s anti-aggregation effect, in combination with its vasodilatational and anti-inflammatory effect, increases the perfusion in the initial critical hours and thus secondarily decreases the reperfusion injury. Received: 21 January 1999 / Accepted: 28 June 1999     

Extracorporal shock wave may enhance skin flap survival in an animal model.

Several methods have been used in an attempt to increase blood supply and tissue perfusion in ischemic tissues. The authors investigated the effect of extracorporal shock wave (ESW) treatment on compromised skin flaps. For this purpose, the epigastric skin flap model in rats, based solely on the right inferior epigastric vessels was used. Twenty male Sprague-Dawley rats were divided into two groups (ESW-group, Control group) of 10 rats each. The ESW-group was administered 2500 impulses at 0.15 mJ/mm(2) immediately after surgery, whereas, the control group received no treatment. Flap viability was evaluated on day 7 after the operation. Standardised digital pictures of the flaps were taken and transferred to the computer, and necrotic zones relative to total flap surface area were measured and expressed as percentages. Overall, there was a significant reduction in the surface area of the necrotic zones of the flaps in the ESW group compared to the control group (ESW group: 2.2+/-1.9% versus control: 17.4+/-4.4% (p < 0.01). In this study, the authors demonstrated that treatment with ESW enhanced epigastric skin flap survival, as confirmed by the significant reduction of necrotic flap zones. ESW treatment seems to represent a feasible and cost effective method to improve blood supply in ischemic tissue.     

一氧化氮对任意型皮瓣成活的影响

目的　观察一氧化氮 (nitricoxide ,NO)对任意型皮瓣成活的影响。方法　采用Wistar大鼠为实验动物 ,在其背部形成 9cm× 3cm任意型皮瓣 ,通过图像分析技术、病理切片、电镜观察、组织化学染色和血清中NO2 - NO3 - 含量的测定等手段 ,观察NO合酶抑制剂 (L NAME)和NO合成前体 (L Arg)对皮瓣成活的影响。结果　术后第 7dL Arg组皮瓣成活率明显高于其他两组 (P <0 0 1)。组织学检查发现L Arg组皮瓣毛细血管扩张及增生明显。结论　促进NO合成能扩张微血管 ,改善微循环 ,提高皮瓣存活率。     

VEGF明胶缓释微球对大鼠背部随意皮瓣存活的影响

目的研究局部注射血管内皮生长因子(VEGF)复合明胶微球对SD大鼠背部随意皮瓣存活的影响.方法采用改良的乳化冷凝法交联制备复合VEGF的明胶缓释微球,将其注射于大鼠背部随意皮瓣,24只SD大鼠随机分为复合VEGF微球组(A组)、VEGF治疗组(B组)和对照组(C组),术后7天分别进行皮瓣存活率、新生血管计数的检测.结果术后7天皮瓣的存活率分别为(68.54±2.79)%,(58.65±3.26)%,(45.43±2.71)%,治疗组存活率显著高于对照组(P＜0.05),且存活质量A组最好;皮瓣内新生血管计数分别为(31.16±4.38),(25.41±4.06),(18.68±5.44)具有显著差异性.结论VEGF缓释微球可以促进缺血皮瓣的血管新生,提升皮瓣存活率.     

bFGF微球对大鼠背部任意皮瓣存活的影响

目的：研究局部注射碱性成纤维细胞生长因子（bFGF）复合明胶微球对SD大鼠背部任意皮瓣存活的影响。方法：采用改良的乳化冷凝法交联制备复合bFGF明胶缓释微球,将其注射于大鼠背部任意皮瓣,24只SD大鼠随机分为bFGF微球组（A组）、bFGF治疗组（B组）和对照组（C组）,术后7天分别进行皮瓣存活率、新生血管计数的检测。结果：术后7天皮瓣的存活率分别为（65.42±2.19）%,（54.38±4.52）%,（45.43±2.71）%,微球组存活率显著高于对照组（P〈0.05）且存活质量最好;皮瓣内新生血管计数分别为28.75±2.36,21.28±3.82,18.68±5.44,具有显著性差异。结论：bFGF缓释微球可以促进缺血皮瓣的血管新生,提高皮瓣存活率。     

Aprotinin in Ischemia-Reperfusion injury: Flap survival and neutrophil response in a rat skin flap model

Multiple drugs have been used in experimental skin flap models to reduce the effects of reperfusion ischemia. The effects of antiproteases, however, have not been studied. A skin flap ischemia reperfusion model was developed in the rat to study the effects that aprotinin, a broad-spectrum antiserine protease, would have on skin flap viability. Thirty-two male rats underwent elevation of a ventral pedicled skin flap based on the superficial inferior epigastric artery. The flaps were subjected to 10 hr of warm ischemia by clamping the neurovascular pedicle followed by reperfusion. Aprotinin or saline (control) was administered systemically via the contralateral femoral vein either before or after the ischemic insult. Full-thickness skin biopsies were obtained at 1, 8, and 24 hr into reperfusion. Biopsies were evaluated for neutrophil concentration (using a myeloperoxidase [MPO] assay) and thromboxane B₂ [TxB₂] content. Flap survival was calculated at 1 week using standardized photography and computer-assisted digital imaging. Aprotinin given before an ischemic insult significantly improved flap survival compared to saline controls (52.3% alive vs. 29.6%, P = 0.0132, unpaired t-test). Aprotinin given after ischemia did not significantly influence flap survival (28.8% vs. 34.4% in saline controls, P = 0.708). MPO levels in the aprotinin preischemia treatment group were significantly less at 1 and 8 hr into reperfusion, indicating decreased neutrophil numbers. No statistical difference in TxB₂ levels was noted in either group at any time after reperfusion. Aprotinin significantly improves skin flap survival when given prior to but not after an ischemic insult. Aprotinin appears to lower the concentration of neutrophils in skin flaps pretreated with the drug. Reperfused skin flap levels of thromboxane B₂ are unaffected by the pre- or postischemic administration of aprotinin. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:354–361, 1998     

水蛭素对大鼠随意型皮瓣存活的影响

目的 研究水蛭素对大鼠背部超长随意型皮瓣存活的影响.方法 采用改良大鼠"McFarlane flap"模型,将实验动物随机分为水蛭素实验组(水蛭素组)和生理盐水对照组(生理盐水组),水蛭素组局部注射3 ml(30 ATU)水蛭素,生理盐水组则注射3 ml生理盐水,连续注射7 d后分别检测两组皮瓣的存活面积百分比,并取皮瓣近、中、远段(即Ⅰ、Ⅱ、Ⅲ区)组织做光镜观察,免疫组化法检测血管内皮生长因子(VEGF)和碱性成纤维细胞因子(bFGF)的表达.结果 术后7 d,水蛭素组皮瓣的存活面积百分比为(69.52±3.23)%,生理盐水组为(50.36±2.37)%,水蛭素组显著高于生理盐水组,差异有统计学意义(P＜0.01);水蛭素组皮瓣坏死与存活并存的Ⅱ区,组织水肿、炎性细胞浸润情况明显比生理盐水组轻.水蛭素和生理盐水组皮瓣Ⅱ区的新生血管计数分别为(28.24±4.23)个/mm2和(17.45±5.43)个/mm2,两组比较差异有统计学意义(P＜0.05).通过计算累积吸光度A值(IA),得到水蛭素和生理盐水组VEGF阳性量分别为9262.23±896.99和4938.05±1623.67,bFGF阳性量分别为5122.83±1176.12和2779.45±472.00,水蛭组VEGF及bFGF的表达均高于生理盐水组,差异均有统计学意义(P＜0.01).结论 水蛭素可能通过体内一系列复杂的调控通路,最终增加VEGF、bFGF表达,促进皮瓣新生血管增生,改善皮瓣血供,减轻炎性反应,降低缺血皮瓣的坏死率,从而提高大鼠随意型皮瓣的存活.

Abstract：

Objective To investigate the effect of Hirudin on random skin flap survival in rats.Methods 24 SD rats were randomly divided into control group and experimental group. The "McFarlane flap(3 cm ×9 cm)" rat models were established on the rat dorsum. 3 ml Hirudin (30 ATU) was injected into the flap in the experimental group, while 3 ml saline in the control group. The injection was performed for 7 days. The flap survival area in the two groups was measured. The tissue samples were taken from proximal( Ⅰ ), middle( Ⅱ ) and distal( Ⅲ ) portions of flaps for histologic study. The VEGF and bFGF expression was also detected with immunohistochemistry method. Results 7 days after operation, the flap survival rate was ( 69.52 + 3.23 )% in the experimental group, while ( 50.36 ± 2.37 )% in control group,showing a significant difference between the two groups ( P ＜ 0.01 ). In the middle portion, tissue edema and infiltration of neutrophils in experimental group was markedly slighter than that in control group. The VEGF and bFGF expression and neovascularization was enhanced markedly in experimental group.Conclusions Hirudin can increase the survival of random pattern skin flaps. It may increase the VEGF,bFGF expression through a series of complex regulatory pathway. Then flap neovascularization is promoted and the flap blood supply is increased.     

Propofol improves skin flap survival in a rat model: correlating reduction in flap-induced neutrophil activity

Accumulation of neutrophils in a random pattern skin flap has been demonstrated to contribute to the necrosis of distal flap tissue. This study proposes that administration of propofol anesthesia can effectively reduce neutrophil activity and enhance skin flap survival. The study was a randomized controlled trial using male Sprague-Dawley rats as subjects. For flap survival studies, a 3- by 12-cm, dorsal, cranial-based, random pattern skin flap was elevated and reapproximated. Flaps were examined for viability 10 days postsurgery. To assess neutrophil activity, flap biopsies were taken 12, 24, or 48 hours postsurgery from distal, middle, and proximal flap regions, and myeloperoxidase enzyme content was analyzed. Animals were randomly assigned to 1 of 4 groups: group 1, ketamine anesthesia (controls); group 2, propofol anesthesia; group 3, ketamine anesthesia plus 10% lipid emulsion (propofol vehicle); group 4, ketamine anesthesia without flap elevation (nonoperated controls for myeloperoxidase study). Flap survival was significantly improved in the propofol group compared with both the ketamine and vehicle control groups (P <0.01). Increased flap viability was correlated with a reduction in myeloperoxidase content in the propofol group compared with control operated animals, with minor variations observed in the different flap regions and time points tested. This study indicates that the use of propofol can potentially improve skin flap survival. The beneficial effects may be attributed to a reduction in neutrophil activity within the flap.     

The effects of VEGF on survival of a random flap in the rat: examination of various routes of administration.

The purpose of the present study was to determine the effects of vascular endothelial growth factor (VEGF) on survival of a full thickness random pattern, McFarlane musculocutaneous flap in the rat. In addition, this study examined a number of different methods of VEGF delivery in an attempt to determine the most effective route of administration. A 2 x 8 cm full thickness dorsal flap with the pedicle remaining attached at the anterior end was elevated in 72 male Sprague-Dawley rats. The rats were randomised into six groups and immediately received the following treatment: Group I (n = 12): systemic VEGF injection into the femoral vein (50 microg/ml); Group II (n = 10): multiple systemic VEGF injections at 0, 24 and 48 h post flap elevation (50 microg/ml); Group III (n = 12): subdermal VEGF injection into the flap (1 microg/ml); Group IV (n = 12): subfascial VEGF injections into the recipient bed (1 microg/ml); Group V (n = 10): topical VEGF onto the recipient bed (1 microg/ml); Group VI (n = 16): control group with no treatment. Following 5 days recovery, the area of flap survival was measured. Mean flap survival ranged from 91% in Group II to 78% in Group V, and was significantly greater in all experimental groups (P< 0.001 for Groups I-IV and P< 0.05 for Group V) as compared to the control group (mean survival of 66%). The only significant difference between the experimental groups was between the mean survival in Group II and Group V (P< 0. 05). Histological analysis demonstrated a qualitatively greater amount of granulation tissue and neovascularisation in the experimental groups. These results support the notion that VEGF rescues tissue at risk of hypoxic damage by inducing angiogenesis, and the use of growth factors such as VEGF holds promise as a method of increasing skin viability.     

The influence of sildenafil on random skin flap survival in rats: an experimental study.

Sildenafil (Viagra), a selective and specific inhibitor of cyclic guanosine monophosphate (cGMP) phosphodiesterases (PDEs), is currently marketed for the treatment of erectile dysfunction. Sildenafil is a potent and highly selective PDE-V inhibitor and enhances smooth muscle relaxation in human. Systemic arterial and venous smooth muscle cells contain PDE-V and nitric oxide (NO) which is a major mediator of relaxation of the smooth muscle cell. The aim of the present study is to investigate, in a rat model, the potential effect of sildenafil on survival of random pattern skin flaps. For this purpose, 32 Sprague-Dawley rats were used and a McFarlane-type caudally based skin flap was designed on the dorsum of the rat (2.5 x 8 cm). Rats were divided into four groups: One control (Group D), and three treatment groups (Groups A, B, C). Sildenafil was administered orally to the experiment groups; Group A: 3 mg/kg/single dose a day, Group B: 10 mg/kg/single dose a day and Group C: 10 mg/kg/twice dose a day. The areas of flap necrosis were measured in each group. The extent of viable flap areas were expressed as a percentage of total flap area, and differences were studied by Completely Randomised Experimental design. The areas of necrosis of skin flaps decreased depending on sildenafil dose, but viability of the flaps treated with 3 mg/kg/day was not different than the control group. The flaps receiving 2 x 10 mg/kg/day sildenafil gave the highest (P < 0.01) survival rate. As a conclusion, sildenafil may have a dose dependent effect to increase flap survival in random skin flaps.     

The effects of nicotinamide and hyperbaric oxygen on skin flap survival.

Hyperbaric oxygen has been established as an acceptable treatment for the chronic healing wound. Nicotinamide has been shown to be angiogenic and accelerate the physiologic process following wounding. Therefore both nicotinamide and hyperbaric oxygen were evaluated to enhance flap survival in an island pedicle skin flap model. These two treatment modalities were evaluated alone and in combination to assess if there is an addictive effect to enhance flap survival. Forty Sprague-Dawley male rats (weight 300-350 grams) were treated for 14 days preoperatively 1 day post-operatively with either 400 mg of nicotinamide i.p. or saline i.p. On day 14, a 7 X 7 cm island pedicle skin flap was elevated ligating the left inferior epigastric neurovascular pedicle and were sutured in their normal position. Twenty animals then underwent hyperbaric oxygen treatments. Forty-eight hours post-operatively animals were re-anesthetized and were given a single injection of fluorescein (25 mg/kg) via the tail vein. The % survival of the flap and SEM of the groups are as follows: Saline 45.67 +/- 31.14, nicotinamide 85.30 +/- 9.24, saline-hyperbaric oxygen 76.70 +/- 9.42 and nicotinamide-hyperbaric oxygen 90.86 +/- 3.94 with statistical significance of p less than 0.01. Nicotinamide appears to be another acceptable therapeutic modality in the management of the acceleration of wound healing.     

Improvement of a long random skin flap survival by application of vascular endothelial growth factor in various ways of local administration in a rat model

Background:

Vascular endothelial growth factor (VEGF) is a heparin-binding glycoprotein which plays a significant role in angiogenesis and vascular permeability. The effect of various ways of local administration of VEGF on random skin flap survival was studied, using flaps with a relatively high length (L) to width (W) ratio (5:1).

Materials and Methods:

An 1.5 × 7.5 cm dorsal skin flap with the pedicle orientated, centered, and remaining attached between the lower angles of the scapulae was elevated in 45 Wistar rats in different phases, depending on the group. Rats were divided in five groups of nine. In group A, injections of saline were administered, in equally divided spaces, into flap''s fascia and transposed to a created skin defect. In group B, injections of VEGF were applied subdermally, in equally divided spaces, within the limits of a predesigned flap, a week prior to flap dissection and transposition. In group C, injections of VEGF were applied into a recipient bed''s fascia just before flap raising and transposition. In group D, injections of VEGF were applied subdermally, only in the distal third of the flap and then the flap was transposed to a recipient area. Finally, in group E, injections of VEGF were applied in the flap intrafascially and in equally divided spaces and then again, the flap was transposed to a recipient area. A week after final flap raising and positioning, rats were euthanatised and flaps were excised. Specimens were photographed, measured, put in formalin 10% and were sent for histological and image analysis.

Results:

Mean flap survival percentage was 35.4% in group A, and 33.7% in group B. In groups C and D, the mean survival area was 56.3% and 80.4%, respectively. In group E, the mean flap survival percentage was 28.3%. Histological analysis demonstrated increased angiogenesis in groups C and D.

Conclusions:

VEGF application improved skin flap survival when injected subdermally in the distal third of a random skin flap or into the fascia of a recipient area even though the length-to-width ratio was high.KEY WORDS: Angiogenesis, flap survival, neovascularisation, skin necrosis, vascular endothelial growth factor     

A new flap model in the rat: the pectoral skin flap

The purpose of this study was to describe a new axial-pattern experimental flap model in the rat. Wistar rats weighing 200 to 250 g were used in the experiment. In 15 rats, the superficial anatomy of the ventral thoracic region was studied by anatomic dissection, dye injection, and microangiography, using 5 rats in each group. The anatomic studies revealed that the ventral thoracic skin derives its principal blood supply from the long thoracic artery--a branch of the common thoracic artery. Based on these anatomic studies, the pectoral skin flap model, pedicled on the long thoracic vessels, was created in the rat. The flap is bounded medially by the midsternal line, laterally by the anterior axillary line, and superiorly and inferiorly by transverse lines passing at the level of the suprasternal notch and the xyphoid process respectively. In 5 animals, bilateral flaps (N = 10) were raised and replaced in situ. In 15 animals, oversized flaps were created by extending the flap for both a greater width (N = 10) and length (N = 10). Although all the flaps limited to the cutaneous territory as described were found to survive totally, oversized flaps underwent partial necrosis distally. The authors conclude that the pectoral flap is a simple and reliable skin flap model for future biological and pharmacological study because it is very easy to raise, has a consistent vascular pedicle, and has well-defined borders with consistent landmarks.     

Effects of low-power laser irradiation on survival of random skin flap in rats

This research was designed to study the effects of low-power helium–neon (He–Ne) laser irradiation on random skin flap survival in rat. Fifty 50 male rats were randomly divided into five groups. On the dorsum of each rat, one full thickness random skin flap which contained no specific vessel was elevated. Groups 1 to 4 were exposed to different models of a low-power He–Ne laser. Group 5 rats received no laser treatment and were considered as the control group. The energy density of the He–Ne laser used was 0.2 J/cm². Immediately after surgery and at day 7, the surface area of all flaps was determined. Histological and tensiometrical studies on the surviving part of the flaps were also performed. The data obtained were analyzed by ANOVA. The results showed a significant difference in the surface area of survival parts of flaps and density of blood vessels on day 7 between group 3 rats and the other groups (P=0.0188, P=0.0455). Low-power He–Ne laser irradiation of flaps without recognized blood vessels in rats, reduced vasospasm, produced vasodilation, and caused a significant increase in the surviving surface area.Presented at the 14th World Congress of the International Society for Laser Surgery and Medicine, India, 27–30th August, 2001     

Dorsal bipedicled island skin flap: a new flap model in mice.

Mice are popular animals for biomedical studies, but few skin flap models have been reported in them. To investigate the ischaemia/reperfusion phenomenon in skin flaps, we first investigated the vascular anatomy of murine dorsal skin and then designed a suitable murine dorsal skin flap model. In 120 mice, six distinct vascular patterns were identified, one being seen in 111 mice (93%). Based on this finding, in Part 2 of the study, 15 mice had flaps (4 x 4 cm) raised based on the two caudal vascular pedicles of the left and right deep circumflex iliac vessels as a bipedicled flap in which the mean (SD) survival was 96 (5)%. In a further 10 mice, flaps were raised based on a single pedicle, the left deep circumflex iliac vessel, as a monopedicled flap, in which the mean (SD) survival was 71 (12)%. The bipedicled flap model was then used to study ischaemia/reperfusion injury. Twenty flaps were subjected to eight hours of ischaemia and subsequent reperfusion, and their mean (SD) survival was 43 (26)%. Histological assessments were also carried out using neutrophil and leucocyte counts, and significant differences between groups were observed.     

Subdermal nitrous oxide delivery increases skin microcirculation and random flap survival in rats

Random skin flaps are essential tools in reconstructive surgery. In this study, we investigated the effect of subdermal nitrous oxide (N₂O) application on random flap survival. In this experimental study, we used 21 female rats in three groups. In the N₂O and air groups, gases were administrated under the proposed dorsal flap areas daily for seven days. Following the treatment period, flaps were raised and inserted back into their place from the dorsal skin. In the control group, the flaps were elevated and inserted back to their place without any pretreatment. Calculation of necrotic flap areas, histological examination and microangiography was performed to evaluate the results 7 days after the flap surgery. The average of necrotic flap area in the N₂O, air and control group was 13.45%, 37.67% and 46.43%, respectively. (N₂O vs air p?=?.044; N₂O vs control p?=?.003). The average number of capillary formations identified in the histological analysis was 7.0?±?1.58, 3.75?±?2.36 and 4.4?±?0.54 in the N₂O, air and control group, respectively. (N₂O vs air p?=?.017; N₂O vs control p?=?.037). The average number of capillary structures identified in the angiography images were 6.3?±?1.52, 1.6?±?1.15 and 1.3?±?0.57 in the N₂O, air and control group, respectively. (N₂O vs air p?=?.04; N₂O vs control p?=?.02). We conclude that subdermal N₂O application increases random flap survival through an increase in the skin microcirculation and could be promising for future clinical applications.     

Combined semimembranosus muscle and epigastric skin flap: a new model of composite-free flap in the rat

We present a new model of combined semimembranosus muscle and epigastric skin free flap based on a single pedicle consisting of the muscular branch of semimembranosus muscle and superficial epigastric vessels in continuity with femoral vessels. In 10 rats, the anatomy of the semimembranosus muscle was studied in detail. The mean length of the muscle was 38 mm and width was 11 mm. The mean weight of the muscle was 1.03 g. The mean external diameter of the femoral artery was 1 mm and vein was 1.2 mm. Eight combined semimembranosus/epigastric skin flaps were dissected and transferred into the neck and contralateral groin regions with 100% success rate. This model of combined muscle and skin flap has several advantages. It is reliable, versatile, easy to dissect with long vascular pedicle and adequate vessel diameter for the anastomoses. It can be used for different applicability, including microcirculatory, pharmacologic, physiological, biochemical, and immunologic studies.