Pharmacologic treatment of the failing skin flap

The Influence of Topical Vasodilator-Induced Pharmacologic Delay on Cutaneous Flap Viability and Vascular Remodeling

BACKGROUND

Surgical delay is a well-described technique to improve survival of random and pedicled cutaneous flaps. The aim of this study was to test the topical agents minoxidil and iloprost as agents of pharmacologic delay to induce vascular remodeling and decrease overall flap necrosis as an alternative to surgical delay.

METHODS

Seven groups were studied (n = 8 in each group), including the following: vehicle, iloprost, or minoxidil before treatment only; vehicle, iloprost, or minoxidil before and after treatment; and a standard surgical delay group as a positive control. Surgical flaps (caudally based modified McFarlane myocutaneous skin flaps) were elevated after 14 days of pretreatment, reinset isotopically, and observed at various time points until postoperative day 7. Gross viability, histology, Doppler blood flow, perfusion imaging, tissue oxygenation measurement, and vascular casting were performed for analysis.

RESULTS

Pharmacologic delay with preoperative application of topical minoxidil or iloprost was found to have comparable flap viability when compared to surgical delay. Significantly increased viability in all treatment groups was observed when compared with vehicle. Continued postoperative treatment with topical agents had no effect on flap viability. The mechanism of improved flap viability was inducible increases in flap blood volume and perfusion rather than the acute vasodilatory effects of the topical agents or decreased flap hypoxia.

CONCLUSIONS

Preoperative topical application of the vasodilators minoxidil or iloprost improved flap viability comparably to surgical delay. Noninvasive pharmacologic delay may reduce postoperative complications without the need for an additional operation.

CLINICAL RELEVANCE STATEMENT

Preoperative use of topical vasodilators may lead to improved flap viability without the need for a surgical delay procedure. This study may inform future clinical trials examining utility of preoperative topical vasodilators in flap surgery.

Postconditioning With Red-Blue Light Therapy Improves Survival of Random Skin Flaps in a Rat Model

BACKGROUND

Random skin flap ischemic necrosis is a serious challenge in reconstructive surgery. Photobiomodulation is a noninvasive effective technique to improve microcirculation and neovascularization. Photobiomodulation with red or blue light has been separately proven to partially prevent skin flap necrosis, but the synergistic effect of red and blue light not been elucidated. Our experiment evaluated the impact of postconditioning with red-blue light therapy on the viability of random flaps.

METHODS

Thirty Sprague-Dawley male rats (male, 12 weeks) with a cranially based random pattern skin flap (3 × 8 cm) were divided into 3 groups: control group, red light group, and red-blue light group. On postoperative day 7, flap survival was observed and recorded using transparent graph paper, flaps were obtained and stained with hematoxylin and eosin, and microvessel density was measured. Micro-computed tomography was used to measure vascular volume and vascular length. On days 0, 3, and 7 after surgery, blood flow was measured by laser Doppler. To investigate the underlying mechanisms, the amount of nitric oxide (NO) metabolites in the flap tissue was assessed on days 3, 5, and 7 after surgery.

RESULTS

The mean percentage of skin flap survival was 59 ± 10% for the control group, 69 ± 7% for the red light group, and 79 ± 9% for the red-blue light group (P < 0.01). The microvessel density was 12.3 ± 1.2/mm2 for the control group, 31.3 ± 1.3/mm2 for the red light group, and 36.5 ± 1.4/mm2 for the red-blue light group (P < 0.01). Both vascular volume and total length in the red-blue light group showed significantly increased compared with the red light and control group (P < 0.01). Blood flow in the red-blue light treated flap showed significantly increased at postsurgery days 3 and 7 compared with the red light and control group (P < 0.01). The level of the NO metabolites was significantly increased in flap tissues belonging to the red-blue light group compared with the other 2 groups (P < 0.01).

CONCLUSIONS

This study showed that postconditioning with red-blue light therapy can enhance the survival of random skin flap by improving angiogenesis and NO releasing.

Flap Venous Congestion and Salvage Techniques: A Systematic Literature Review

Venous congestion is a frequent problem in flap surgery. Other than surgical revision, there are a multitude of procedures in the literature to tackle this problem, but their effectiveness is not clear. Through a systematic review, we aimed to identify and evaluate the different interventions available for managing flap venous congestion.

Methods

The MEDLINE, PubMed central, Embase, and Cochrane databases were searched. The study selection process was adapted from the PRISMA statement. All English and French original articles describing or comparing a method for managing flap venous congestion were included. For each article, a level of evidence was assigned, as defined by the Oxford Centre for Evidence-based Medicine. Lastly, we specifically analyzed the effectiveness of postoperative non-surgical methods. No formal analysis was performed.

Results

Through literature searches carried out in various databases, we identified 224 articles. Finally, 72 articles were included. The majority of these studies had a low-level evidence. A total of 17 different methods (7 pre- and intraoperative, and 10 postoperative) were found. Concerning non-surgical methods, the most represented were leeches, local subcutaneous injection of heparin with scarification, venocutaneous catheterization, negative pressure therapy, and hyperbaric oxygen therapy.

Conclusions

Risks of venous congestion of flaps must always be present in a surgeon's mind, at every stage of flap surgery. Apart from studies on the use of leeches, which have a significant follow-up and large enough patient numbers to support their efficacy, the low-level evidence associated with studies of other methods of venous congestion management does not allow us to draw a scientifically valid conclusion about their effectiveness.

Comparison of the effects of systemic sildenafil, tadalafil, and vardenafil treatments on skin flap survival in rats

OBJECTIVE

The most important issue in flap surgery is flap viability. This study aimed to compare the effects of most commonly used phosphodiesterase type 5 (PDE5) inhibitors on flap survival.

METHODS

A 3 × 9 cm flap was elevated from the dorsum of 32 Wistar albino rats. In the control group, saline was administered 2 hours before the flap elevation and continued for 2 days after the surgery. In the sildenafil, tadalafil, and vardenafil groups, the related drug was administered. Blood flow in the flaps was monitored with laser Doppler flowmetry. On postoperative day 7, flaps were photographed and biopsies were obtained.

RESULTS

The ratios of flap necrosis area in the tadalafil, sildenafil, and vardenafil groups were lower than that in the control group, but without significant difference (p = 0.077). Histopathological evaluation revealed no significant difference among the groups.

CONCLUSION

The ratio of flap necrosis area tended to be lower in the groups receiving oral PDE5 inhibitors than in the control group, although not statistically significant. The role of PDE5 inhibitors needs to be evaluated in larger studies before a conclusion can be made regarding their effects on flap viability.

Improvement of tissue survival of skin flaps by 5α-reductase inhibitors: possible involvement of nitric oxide and inducible nitric oxide synthase

Background:

Skin flap grafting is a popular approach for reconstruction of critical skin and underlying soft tissue injuries. In a previous study, we demonstrated the beneficial effects of two 5α-reductase inhibitors, azelaic acid and finasteride, on tissue survival in a rat model of skin flap grafting. In the current study, we investigated the involvement of nitric oxide and inducible nitric oxide synthase (iNOS) in graft survival mediated by these agents.

Methods:

A number of 42 male rats were randomly allocated into six groups: 1, normal saline topical application; 2, azelaic acid (100 mg/flap); 3, finasteride (1 mg/flap); 4, injection of L-N^G-nitroarginine methyl ester (L-NAME) (i.p., 20 mg/kg); 5, L-NAME (20 mg/kg, i.p.) + azelaic acid (100 mg/flap, topical); 6, L-NAME (20 mg/kg, i.p.) + finasteride (1 mg/flap, topical). Tissue survival, level of nitric oxide, and iNOS expression in groups were measured.

Results:

Our data revealed that azelaic acid and finasteride significantly increased the expression of iNOS protein and nitric oxide (NO) levels in graft tissue (P < 0.05). These increases in iNOS expression and NO level were associated with higher survival of the graft tissue.

Conclusion:

It appears that alterations of the NO metabolism are implicated in the azelaic acid- and finasteride-mediated survival of the skin flaps.

Long-term enteral arginine supplementation in rats with intestinal ischemia and reperfusion

BACKGROUND

The effects of short-term enteral arginine supplementation on intestinal ischemia-reperfusion (IR) injury have been widely studied, especially the ischemic preconditioning supplementation. The aim of this study was to investigate the effects of long-term intra-duodenal supplementation of arginine on intestinal morphology, arginine-associated amino acid metabolism, and inflammatory responses in rats with intestinal IR.

MATERIALS AND METHODS

Male Wistar rats with or without three hours of ileal ischemia underwent duodenal cannulation for continuous infusion of formula with 2% arginine or commercial protein powder for 7 d. The serological examinations, plasma amino acid and cytokine profiles, and intestinal morphology were assessed.

RESULTS

Intestinal IR injury had significant impacts on the decreases in circulating red blood cells, hemoglobin, ileum mass, and villus height and crypt depth of the distal jejunum. In addition, arginine supplementation decreased serum cholesterol and increased plasma arginine concentrations. In rats with intestinal IR injury, arginine supplementation significantly decreased serum nitric oxide, plasma citrulline and ornithine, and the mucosal protein content of the ileum.

CONCLUSIONS

These results suggest that long-term intra-duodenal arginine administration may not have observable benefits on intestinal morphology or inflammatory response in rats with intestinal ischemia and reperfusion injury. Therefore, the necessity of long-term arginine supplementation for patients with intestinal ischemia and reperfusion injury remains questionable and requires further investigation.

Angiogenesis and plastic surgery

SUMMARY

Angiogenesis, the formation of new blood vessels from an existing vascular bed, is a normal physiological process which also underpins many--apparently unrelated--pathological states. It is an integral factor in determining the success or failure of many procedures in plastic and reconstructive surgery. As a result, the ability to control the process would be of great therapeutic benefit. To appreciate the potential benefits and limitations of recent advances in our understanding of angiogenesis, it is important to comprehend the basic physiology of blood vessel formation. This review aims to summarise current knowledge of the way in which angiogenesis is controlled and to look at how disordered vessel development results in pathology relevant to plastic surgery. Through this we hope to provide a comprehensive overview of the recent advances in angiogenesis as they relate to plastic surgery, particularly the promotion of flap survival, tendon healing, nerve regeneration, fracture healing and ulcer treatments.

Dipyrone increases the blood flow of arterial dorsal skin flaps

BACKGROUND

Findings have shown that dipyrone has a beneficial effect on skin flap survival. A pharmacologic explanation for this effect points to its vascular smooth muscle-relaxing effect. This study evaluated the effect of dipyrone on blood flow and thus survival of rat random dorsal skin flaps.

METHODS

For this study, 27 male Wistar albino rats were randomly assigned to control (treated with sterile saline) and treatment (treated with dipyrone 100 mg/kg) groups. A random dorsal skin flap measuring 4 x 10 cm was raised in each animal. The edges of the flap were sutured back into their original place. Dipyrone treatment continued at 100 mg/kg per day during the 7-day observation period. Blood flow was recorded by laser Doppler preoperatively (baseline), immediately after the flap was sutured back to its original position (acute), and on postoperative day 7. The degree of necrosis was evaluated by the grid method on day 7. Mean percentage necrosis and minimum laser Doppler readings were compared between the two groups.

RESULTS

A significant increase in blood flow was observed in the dipyrone group at the acute phase but not on postoperative day 7. The percentage of the necrotic area was lower in the treatment group. However, it did not reach the significance level (p = 0.09).

CONCLUSION

Dipyrone significantly increases [corrected] skin blood flow at the acute phase of flap elevation although the necrotic area does not reach the significance level.

[Vacuum-assisted closure therapy. Current status and basic research]

The gap between the broad clinical use of vacuum-assisted closure therapy (VT) and knowledge of the physiological mechanisms leading to its effectiveness is great. The value of the technique and its future development are dependent on research into these mechanisms. A meta-analysis evaluating the results of basic research on the effectiveness of VT was carried out based on peer reviewed publications. This is considered in relation to other therapeutic approaches of basic research to wound healing (growth factors etc.). Our study includes a concise description of the scientific background to the mechanisms of cell stimulation using basic work on tissue expansion, bone, vessel and nerve distraction as well as in vitro cell stimulation. Evaluation of the scientific data on all known effects of VT was made based on the results from experimental animal studies, the results of randomized clinical studies, observations on clinical applications and case reports. Assessment of the studies was based on design and significance as well as the appraisal of our own clinical experience. Data involving cellular effects (proliferation, synthesis, wound healing), systemic effects (mediators, systemic inflammatory disease), extracellular effects (perfusion, edema, local wound environment, stabilization, barriers) and complex effects of VT (inflammation, matrix function, blood supply) were examined. Systematic analysis of the data allows scientifically interested surgeons rapid access to the theme, the first, to this extent, extensive overview of the current scientific situation as well as a comprehensive bibliography for all areas involving the theme of mechanical cell stimulation. The authors list major areas for future research and encourage the development of multicenter studies.

Effects of clopidogrel on survival of rat skin flaps

Clopidogrel is a thienopyridine derivative that is chemically related to ticlopidine, which irreversibly inhibits platelet aggregation by selectively binding to adenylate cyclase-coupled adenosine diphosphate receptors on the platelet's surface. In animal models, clopidogrel has been shown to reduce the incidence of both arterial and venous thrombi. In the present study the effects of clopidogrel on the survival of rat epigastric island flaps was researched. Epigastric island flaps of 7x7cm were raised from symphisis pubis to arcus costa with the panniculus carnosus. The experimental group received seven doses of 25mg/kg clopidogrel postoperatively, the first dose given immediately after the suturing of the flaps. The rats were anaesthetised on postoperative day 7 to assess the survival of flaps. The difference between the clopidogrel and the control group was significant (P<0.005). The full-thickness skin samples obtained after the calculation of survival percentages revealed thinning of the epidermis layer and active chronic inflammation in both groups. However, diffuse dilated vessels, extravasated eritrocytes were seen in the clopidogrel group flaps. The results indicated a significant increase in flap survival in rats given clopidogrel. Further research is needed to assess the critical doses of clopidogrel to create optimal flap survival improvement.

Vakuumtherapie und Defektdeckung beim Weichteiltrauma

This study presents the results of a meta-analysis based on the literature dealing with the clinical applications of vacuum-assisted closure (VAC) in the areas of chronic wounds, acute posttraumatic wounds, compartment syndromes, or injuries of the upper extremities. The studies were analysed for validity, significance of conclusion with respect to success rate, publications, and economic efficacy. The data show that with VAC a very valuable technique has been added to an integrated therapeutic concept of soft tissue reconstruction. However, clinical data from prospective randomised trials to support some of the positive aspects seen in the daily clinical application of the technique are still missing. These would create a sound basis demonstrating the economic efficacy of the technique.

Rat epigastric flap survival and VEGF expression after local copper application

BACKGROUND

Copper has been used in wound healing since ancient times, and copper insufficiency seems to impair wound healing. Much less is known about the local effects of copper application on wound healing.

METHODS

The authors studied 30 male Sprague-Dawley rats weighing between 250 and 350 g for 5 days. Full-thickness random skin flaps, measuring 1.5 x 7.5 cm, were elevated on the epigastric region. The rats were randomized into two groups according to the local treatment that was used. In group 1 (20 animals), 1 ml of copper ointment was applied on the flap bed after flap suturing. In group 2 (10 animals), 1 ml of placebo ointment (petroleum jelly) was used. Intraperitoneal injection of 30 mg/kg body weight of Hypoxyprobe-1 was performed in each rat on the fourth postoperative day and all animals were killed 3 hours later. Histologic examination of the distal end of the flaps was used for detection of hypoxic tissue changes. Expression, density, and extent of vascular endothelial growth factor activity was detected with the aid of immunocytochemistry.

RESULTS

All rats survived throughout the study period. This experimental study showed that local application of copper at the random flap bed may promote wound-related angiogenesis by inducing vascular endothelial growth factor expression. The authors demonstrated statistically significant flap survival after local copper application at the flap bed.

CONCLUSION

The marked benefits of copper application in flap survival in this experimental model may guarantee its clinical application in flaps with questionable viability.

Perfusion, viability, and pedicle dependence in acute and delayed rat island skin flaps

PURPOSE

Although surgical delay phenomenon has been widely investigated, its pathophysiology has not been fully elucidated.

METHODS

In 25 Spraque-Dawley rats, an 8 x 8 cm2 epigastric skin flap consisting of 4 vertical zones A through D (farthest from vascular pedicle) was outlined. All animals were perfused twice with colored fluorescent microspheres: immediately before and after flap elevation (Acute, n = 10) and before and after pedicle ligation on POD 8 (Delayed, n = 15).

RESULTS

After acute flap elevation, peripheral perfusion dropped significantly in zone C (0.29 +/- 0.01 vs. 0.19 +/- 0.04 ml g(-1) min(-1); P < 0.01) and zone D (0.33 +/- 0.09 vs 0.01 +/- 0.01 ml g(-1) min(-1); P < 0.01), while global flap perfusion remained unchanged. Total and regional blood flow did not change in the Delayed group after pedicle ligation.

CONCLUSIONS

Elevation of a pedicled flap caused significant decrease in distal flap perfusion while maintaining proximal and total flap perfusion. Eight-day delay was adequate to establish sufficient flap perfusion independent of the vascular pedicle.

Short- and Long-Term Effects of Sildenafil on Skin Flap Survival in Rats

OBJECTIVE

Distal ischemic necrosis of the flap remains an unsolved, challenging problem. Phosphodiesterase (PDE) inhibitors, which include the drug sildenafil, are a relatively new class of U.S. Food and Drug Administration-approved medications whose effect on tissue viability has not been widely explored. The vasodilatory effects of these drugs have the potential to enhance blood flow to flaps and increase their survivability. The purpose of this study was to examine the short- and long-term effects of sildenafil, administered intraperitoneally at a dose of 9 mg/kg per day, on the survival of surgical skin flaps in rats.

METHODS

A McFarlane-type random pattern skin (3 x 10-cm) flap model was used to evaluate the effect of sildenafil on necrosis at multiple time points. Rats were assigned to sildenafil-treated (9 mg/kg per day intraperitoneally; n = 34), vehicle control (n = 35), or sham (no injection; n = 40) groups. In each group, caudally based, dorsal, rectangular (3 x 10-cm) flaps were created. Flap necrosis was determined using orthogonal polarization spectral imaging and digital photography analysis on days 1, 3, 5, and 7 postsurgery.

RESULTS

Orthogonal polarization spectral imaging results showed a significant decrease in necrosis and stasis in rats treated with sildenafil on days 1 and 3. Although reductions observed at days 5 and 7 were not as dramatic as days 1 and 3, digital photography analysis confirmed a decrease in the area of necrosis at all time points evaluated.

CONCLUSIONS

These results suggest that PDE 5 inhibitors may play a more important role in early postoperative skin flap viability rather than at later time points and may be beneficial for skin flap viability as shown in the rat model. PDE 5 inhibitors may reduce the extent of necrosis after reconstructive surgeries.

Effect of sildenafil citrate on viability of flaps: an experimental study in rats

Various pharmacological agents have been used to try and elucidate the pathophysiology of ischaemia and necrosis of flaps. Their most important disadvantage is the need for relatively high doses given systemically, which increases the risk of potential side effects. Topical or local agents are more useful. Sildenafil citrate, the specific inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE 5) was studied as an antianginal drug during the late 1980s, but is now used for its effect on erectile function in men. Sildenafil citrate causes dilatation of peripheral arteries and veins and the inhibition of the thrombus-forming ability of platelets in vivo. Our study was designed to test the efficacy of sildenafil citrate on the viability of flaps.

Comparison of the effectiveness of gene therapy with transforming growth factor-beta or extracorporal shock wave therapy to reduce ischemic necrosis in an epigastric skin flap model in rats

The induction of neoangiogenesis by exogenous growth factors in failing skin flaps has recently yielded promising results. Gene transfer with virus vectors has been introduced as a highly capable route of administration for growth factors, such as vascular endothelial growth factor or fibroblast growth factor. Extracorporal shock waves (ESW) deliver energy by means of high amplitudes of sound to the target tissue and have been shown to induce angiogenesis. We compared the effectiveness of gene therapy with adenovirus-mediated transforming growth factor-beta (TGF-beta) and ESW therapy to treat ischemically challenged epigastric skin flaps in a rat model. Thirty male Sprague-Dawley rats were divided into three groups of 10 each with an 8 x 8 cm epigastric skin flap. Rats received either subdermal injections of adenovirus (Ad) encoding TGF-beta (10(8) pfu) or ESW treatment with 750 impulses at 0.15 mJ/mm2. The third group received no treatment and served as a control group. Flap viability was evaluated after 7 days and digital images of the epigastric flaps were taken and areas of necrotic zones relative to total flap surface area calculated. Histologic evaluation and increased angiogenesis were confirmed by CD31 immunohistochemistry. Overall, there was a significant increase in mean percent surviving area in the Ad-TGF-beta group and the ESW group compared to the control group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0% and control group: 82.6 +/- 4.3%; p < 0.05). Furthermore, in the ESW group mean percent surviving areas were significantly larger than in the Ad-TGF-beta group (ESW group: 97.7 +/- 1.8% vs. Ad-TGF-beta: 90.3 +/- 4.0%; p < 0.05). Flap vascularization was increased by Ad-TGF-beta and ESW with numerous vessels, however, there was no significant difference between the two treatment groups. We conclude that treatment with ESW enhances epigastric skin flap survival significantly more than Ad-TGF-beta treatment and thus represents a modality that is feasible, cost-effective, and less invasive compared to gene therapy with growth factors to improve blood supply to ischemic tissue.

Enhancement of dorsal random-pattern skin flap survival in rats with topical lidocaine and prilocaine (EMLA): Enhancement of flap survival by EMLA

BACKGROUND

Various topical pharmacologic agents have been investigated for their efficacy in preventing or reversing skin flap ischemia. Most of these studies have focused on agents that act on the vascular smooth muscles to cause vasodilatation and improve circulation in the flap. Most of local anesthetics relax vascular smooth muscle and produce peripheral vasodilatation. Topical lidocaine administration was shown that it was an effective and prompt resolution of mechanically induced vasospasm. The topical analgesia cream, EMLA is a mixture of the substances lidocaine and prilocaine. EMLA causes a biphasic vascular response comprising initial blanching and vasoconstriction (maximal after 1.5 h of application) and late erythema and vasodilatation at application times longer than 3 h.

MATERIALS AND METHODS

To investigate the effect of EMLA on random flap survival, 40 rats were divided in 2 groups of 20 animals. Caudally based random pattern skin flaps were elevated on dorsa of the rats in 10 x 3 cm dimensions. In group 1 which was the treatment group, topical EMLA was applied and covered with Opsite for 1 week whereas in group 2 which was the control group, carrier for EMLA was applied to the flaps. At the end of treatment period, the areas of flap necrosis were measured and percentages of flap survivals were calculated.

RESULTS

The mean percentages of flap survivals in group 1 and 2 were 81.2 +/- 1.2 percent and 58.7 +/- 2.3 percent, respectively.

CONCLUSION

Topically administered EMLA might lead to a significant improvement in flap survival. In addition, it is safe, cost-effective, easily applied, and clinically available.

Efficacy of the flashlamp-pumped pulsed-dye laser in nonsurgical delay of skin flaps

OBJECTIVE

The purpose of this article was to determine the effectiveness of laser delay by use of the flashlamp-pumped pulsed-dye laser operating at a wavelength of 585 nm; to elucidate the comparable or dissimilar macroscopic, microscopic, and hemodynamic changes between laser and surgical delay methods; and to clarify the possible mechanisms underlying the delay effect of laser.

METHODS

A standardized caudally based random dorsal rat flap model was used in this study: Acute random skin flaps served as control subjects (group 1). Surgical delay was employed by incision of lateral longitudinal borders both without (group 2) and with (group 3) undermining, and laser delay methods were performed by laser irradiation of both lateral longitudinal borders (group 4) and the entire surface (group 5) of the proposed flap. Evaluation was done by histologic examination, India ink injection, laser Doppler perfusion imaging, and measurement of flap survival.

RESULTS

Histologically, dilation and hypertrophy of subpapillary and subdermal vessels were evident in groups 2, 3, and 4; on the other hand, degranulation of mast cells in the vicinity of occluded vessels at the 1st hour of laser delay and a striking mast cell proliferation and degranulation in association with newly formed vessels (angiogenesis) at the 14th day of laser delay were prominent in group 5. India ink injections revealed longitudinally arranged large-caliber vessels and cross-filling between the vessels of adjacent territories in groups, 2, 3, and 4, but only small-caliber vessels in group 5. Compared with the acute flaps, both surgical and laser delay significantly increased the mean flap perfusion to the maximal levels after a 14-day delay period, and all delay procedures improved flap survival; the most significant increase in surviving area was observed in group 3, whereas the less significant increase in surviving area was in group 5.

CONCLUSION

This study demonstrates that laser delay is as effective as surgical delay and that laser delay by lasering lateral borders leads to dilation and longitudinal rearrangement of the existing vessels rather than angiogenesis, whereas laser delay by lasering the entire surface results in delay effect by inducing angiogenesis due to activation and degranulation of the mast cells.

Local administration of nitric oxide donor significantly impacts microvascular thrombosis

OBJECTIVES/HYPOTHESIS

Clinical pharmacotherapy has demonstrated a role in preventing microvascular thrombosis in both experimental and clinical settings. Previous studies in the rabbit model have noted an increased rate of thrombosis with intravenous infusion of nitric oxide antagonists. The study assessed the effects of local application of nitric oxide agonists and antagonists on microvascular anastomotic patency rates.

STUDY DESIGN

A randomized, prospective analysis.

METHODS

An arterial inversion graft microvascular thrombosis model was used in New Zealand white rabbits. The rabbits were randomly assigned to nitric oxide agonist, antagonist, and control groups. In each rabbit, the common femoral artery was surgically exposed and a 2-mm arterial inversion graft was harvested. The anastomosis of the graft to the common femoral artery was performed in solutions of either 100 micromol/L spermine NONOate (nitric oxide donor), 100 micromol/L nitro-L-arginine-methyl ester (L-NAME) (nitric oxide synthase inhibitor), or 0.9% sodium chloride (control) solution. The contralateral common femoral artery also underwent arterial inversion graft testing with the use of the same solution. Arterial patency was assessed 1 hour after anastomosis.

RESULTS

Sixteen of 22 arterial inversion grafts performed in the spermine NONOate solution remained patent, and 6 of 22 clotted. Eleven of 21 arterial inversion grafts performed in the control solution remained patent, and 10 clotted. Seven of 21 arterial inversion grafts performed in the L-NAME solution remained patent, and 14 clotted. These results were found to be statistically significant using the chi test with a value of less than.05.

CONCLUSIONS

In the rabbit model, local application of nitric oxide agonists and antagonists can significantly impact anastomotic patency rates. Further studies may demonstrate a role for the clinical use of nitric oxide in microvascular surgery.

Improved dorsal random-pattern skin flap survival in rats with a topically applied combination of nonivamide and nicoboxil

The effects of a topically applied combination of nonivamide and nicoboxil in improving skin perfusion and preventing distal flap necrosis were tested in a random-pattern dorsal skin flap model. Forty male Wistar rats were randomized into two groups (n = 20), and a standardized dorsal random-pattern skin flap was raised on each rat. Animals in the experimental group were treated with the topically applied drug combination four times per day for 6 days, whereas in the control group only a placebo ointment was applied each time. Skin flap viability was evaluated on day 7, and the extent of skin flap necrosis was compared between the two groups. The topically applied combination of nonivamide and nicoboxil resulted in a statistically significant decrease in skin flap necrosis, compared with the control group (mean percentage of skin flap necrosis in the nonivamide/nicoboxil-treated group, 22.6 +/- 6.0 percent; control group, 36.8 +/- 4.3 percent; p< 0.05). The topical combination of nonivamide and nicoboxil was effective in reducing ischemic necrosis in failing random-pattern skin flaps in this rat model. The results of this study suggest that such a topical drug application might have significant effects in the reduction of ischemic necrosis in the distal parts of skin flaps, and this treatment might also have applications as prophylactic therapy for risky skin flaps.

Expression of endothelin 1 in rat random-pattern skin flaps treated with topical nifedipine

OBJECTIVE

To evaluate the relative tissue concentrations of the endogenous vasoactive peptide endothelin 1 (ET-1) in random-pattern skin flaps (RPSF) treated with either topical anti-ischemic drug therapy (nifedipine) or placebo.

DESIGN

Prospective, randomized, placebo-controlled therapeutic trial.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTION

Experimental subjects underwent caudally based RPSFs using the modified McFarlane technique. Subjects received either topical anti-ischemic drug therapy (nifedipine; n = 6) or inert carrier ointment (placebo; n = 6). Treatment was initiated immediately following flap closure and continued every 6 hours for 5 days. At the end of the treatment period, the animals were killed and the concentration of ET-1 was determined using enzyme-linked immunosorbent assay. Representative tissues from nifedipine- and placebo-treated skin flaps were also analyzed for ET-1 using immunohistochemical stains.

RESULTS

The ET-1 levels in the distal (necrotic) flap segments were increased by 4.53 pg/mL over baseline (nonnecrotic) flaps in the placebo-treated animals and decreased by 4.70 pg/mL below baseline in the nifedipine-treated group (P =.03).

CONCLUSIONS

The correlation between tissue levels of ET-1 and the severity of tissue necrosis suggests that ET-1 may play a pivotal role in ischemic injury of RPSFs. Moreover, treatment with topical nifedipine may antagonize the vasoconstrictive effects of ET-1. Although immunohistochemical analysis revealed ET-1 staining within the flap microvasculature, no quantitative differences were detected between the nifedipine- and placebo-treated flaps. Further studies are needed to define the role of ET-1 in RPSF necrosis.

Inhibitors of nitric oxide promote microvascular thrombosis

BACKGROUND

Microvascular free tissue transfer is a widely utilized method of head and neck reconstruction. Despite advances in the field, reports of experienced microvascular surgeons on large series of free flap procedures reveal that the incidence of free flap failure varies between 5% and 9%. Most cases of free flap failure are initiated by platelet-mediated events that result in thrombosis at the microvascular anastomoses. Recent evidence indicates that nitric oxide (NO) plays a critical role in preventing thrombosis by inhibiting platelet adhesion and aggregation. The role of NO in microvascular anastomotic thrombosis has not been studied.

OBJECTIVE

To determine the role of NO in microvascular thrombosis using an in vivo rabbit model.

METHODS

An arterial inversion graft (AIG)-induced microvascular thrombosis model was utilized in New Zealand white rabbits. The femoral arteries were used bilaterally to create 3-mm AIGs. Intravenous NO donor, NO inhibitor, or isotonic sodium chloride solution (control) was administered for 1 hour following the completion of the AIG, and vessel patency was then checked using a direct "milking test." Sixteen rabbits (32 AIGs) were used as controls. A potent NO inhibitor, N(w)-nitro-L-arginine methylester (L-NAME), was administered to 13 rabbits (26 AIGs) and L-arginine, a NO precursor/donor, was given to 10 rabbits (20 AIGs).

RESULTS

The control animals had a thrombosis rate of 46.9%. The rate of thrombosis in animals exposed to an NO inhibitor (L-NAME) was significantly higher, at 76.9% (P<.05, chi( 2) = 4.23). The L-arginine group did not show a statistical difference with the control in the rate of thrombosis (50.0%).

CONCLUSIONS

Nitric oxide plays a role in microvascular anastamotic thrombosis. Intravenous NO inhibitors appear to increase the short-term rate of microvascular thrombosis. L-arginine, an NO precursor, does not appear to produce the opposite effect. Further studies using local NO donors and antagonists as well as more potent NO precursors are needed to further evaluate NO's role in microvascular thrombosis. The results of this study may have applications to human microvascular surgery.

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.

Arterial blood flow and microcirculatory changes in the rat groin flap after ischemia provocation by electrical stimulation of the artery

An island groin flap based on the inferior epigastric vessels was raised in 10 rats in order to monitor simultaneous ischemic changes in arterial blood flow and skin microcirculation induced by electrical stimulation of the feeding artery. A modified laser Doppler perfusion system recorded blood flow in the epigastric artery and in the skin microcirculation of the flap before and for 40 min after the experimentally induced ischemia. Sections of the stimulated segment of the vessel were obtained at the end of the experimental procedure for histological analysis to determine the extent of endothelial changes, if any. Artery blood flow and the flap microcirculation decreased significantly immediately after stimulation, both slowly increasing to prestimulation levels after 30 min. Artery perfusion was quicker than microcirculation to recover to the baseline value, indicating that reperfusion of larger vessels could involve mechanisms fundamentally different from those active in the resolution of ischemia at the capillary level. Histological artery examination revealed no significant endothelial damage at the stimulation site, thus demonstrating that electrical stimulation induces reproducible ischemia without visible endothelial damage. The differential effects on the feeding artery and on capillary perfusion indicate recruitment of several different mechanisms.

Complications, salvage, and enhancement of local flaps in facial reconstruction

Complications are part of every surgical procedure and their occurrences are inevitable if the surgeon performs enough operations during his/her lifetime. Learning how to prevent complications and how to manage them when they occur are as important as learning how to perform any given surgical procedure. This is especially true in facial reconstruction with local flaps, as complications threaten not only the functional restoration of the integrity, but also the cosmetic appearance of the patient. This article describes common complications and their underlying mechanisms seen in facial reconstruction with local flaps as well as their treatment or prevention, when possible.

Analysis of nitric oxide activity in prevention of reperfusion injury

This project was designed to determine the role of nitric oxide (NO) in the prevention of ischemia-reperfusion injury. Inferiorly based rectus abdominis muscle flaps were elevated in pigs and subjected to 6 hours of ischemia followed by 4 hours of reperfusion. Group I animals received a bolus of L-arginine before reperfusion, and a continuous infusion once flow was restored. Group II animals served as controls and received an equal volume of saline as a bolus and subsequent continuous infusion. Microdialysis was used to measure tissue NO levels, and these were correlated with muscle survival determined by vital staining with nitroblue tetrazolium. The results demonstrated a significant increase in tissue NO levels in L-arginine-supplemented animals (p < 0.05), which in turn correlated with a significant increase in muscle survival (p = 0.0051). These results suggest that administration of supplemental L-arginine to ischemic skeletal muscle during reperfusion results in increased NO production and decreased tissue damage.

The effect of dipyrone on survival of skin flaps

The effect of dipyrone on the skin flap survival was studied in a model of an epigastric island flap with a random extension on the opposite side in 23 rats. Dipyrone was given intraperitoneally one hour before the skin flap was raised. At the end of the operation the depth of penetration of the fluorescein dye in the skin flap was assessed visually from photographic records and the flap survival area was measured by a grid method on the seventh postoperative day. There was a significant reduction in the amount of ischaemic necrosis of the skin flap after a single dose of dipyrone 50 mg/kg (p < 0.001). These data suggest that dipyrone is a useful agent in the prevention and treatment of ischaemia and necrosis of the skin flap.

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.

Axial pattern flap based on the cutaneous branch of the superficial temporal artery in dogs: an experimental study and case report

OBJECTIVE

To determine the anatomic guidelines and viability of an axial pattern flap based on the cutaneous branch of the superficial temporal artery (STA) in dogs. Application of the flap in a clinical patient is reported.

STUDY DESIGN

Flap viability in control and experimental groups was determined 7 days postoperatively.

ANIMALS

A total of 14 mature, mesaticephalic dogs; 1 clinical patient.

METHODS

The cutaneous branch of the STA and vein were incorporated in the flaps of the experimental groups (group A, n = 5; group B, n = 4) and were ligated in the control group (n = 5). Flap length was extended in experimental group B. Seven days postoperatively, the length and area of tissue that remained viable in each flap was determined and compared with similar measurements performed intraoperatively. Cutaneous fluorescence was also used postoperatively to assess flap perfusion. The flap used in the clinical patient had the same dimensions as flaps developed in group A.

RESULTS

Mean survival length (+/- SD) of STA flaps [group A, 9.1 (0.8) cm], was significantly increased (P < .05) compared with control flaps [7.0 (0.6) cm]. Percentage flap length survival (+/- SD) of STA flaps [group A, 91.8 (8.9)%], was significantly increased (P < .05) compared with control flaps [71.6 (7.0)%]. Mean percentage area of survival (+/- SD) of STA flaps [group A, 93.1 (7.5)%], was significantly increased (P < .05) compared with control flaps [73.5 (7.4)%]. Group B flaps had a mean survival length of 10.4 (1.1) cm, percentage flap length survival of 69.5 (4.8)%, and mean percentage area of survival of 69.1 (6.5)%. There was no positive correlation between the area of flap fluorescence at days 0, 1, and 3, and the area of flap survival. Application of the flap in a clinical patient allowed primary wound reconstruction with 100% survival.

CONCLUSION

A flap based on the cutaneous branch of the STA may be a source of skin for reconstructive procedures of the maxillofacial region in dogs.

CLINICAL RELEVANCE

Knowledge of the anatomic landmarks and expected viability of a STA axial pattern flap is essential before consideration of its use as a reconstructive surgical technique.

Effect of parenteral pentoxifylline and topical nitroglycerin on skin flap survival

Flap necrosis is still a significant complication in all types of flap surgery. The effect of parenteral pentoxifylline and nitroglycerin in improving survival of ischemic skin flaps was tested in Wistar rats. In the control group (n = 15) the mean viable length of the flaps was calculated to be 6.160 +/- 0.936, and nonnecrotic flap area was found to be 1859.1 +/- 269.3. In the group treated with pentoxifylline and nitroglycerin (n = 15), the mean viable length of the flap was calculated to be 6.907 +/- 0.617, and the mean nonnecrotic flap area was found to be 2078.5 +/- 172.7. In this study results showed that the use of parenteral pentoxifylline and topical nitroglycerin is effective on skin flap survival.

Comparison of topical anti-ischemic agents in the salvage of failing random-pattern skin flaps in rats

OBJECTIVE

To determine the efficacy of topical anti-ischemic drug therapy in the salvage of failing, random-pattern skin flaps.

DESIGN

Prospective, randomized, placebo-controlled, therapeutic trial.

SETTING

Academic medical center.

SUBJECTS

Sixty-one adult male Sprague-Dawley rats.

INTERVENTION

Each experimental rat underwent a caudally based random-pattern skin flap using the modified McFarlane technique. Rats were randomized to 1 of 6 treatment groups: topical nifedipine, topical trolamine salicylate, topical nitroglycerin, topical trolamine salicylate-nitroglycerin combination, topical nifedipine-trolamine salicylate-nitroglycerin combination, or inert carrier ointment (control). Treatment was initiated immediately following flap closure and continued every 6 hours for 7 days. At the end of the treatment period, animals were euthanized and flap survival was determined for each one.

RESULTS

Topical anti-ischemic drug therapy resulted in a statistically significant reduction in ischemic flap necrosis for each drug (or combination) tested relative to the 44.2% mean necrosis observed in control animals. Treatment with the combination of topical nitroglycerin and topical trolamine salicylate resulted in the best salvage response (25.2% mean necrosis) with a statistically significant improvement in flap survival relative to both controls and nitroglycerin alone.

CONCLUSIONS

Topical anti-ischemic agents are effective in reducing ischemic necrosis of failing, random-pattern skin flaps in the rat model. Although nitroglycerin, trolamine salicylate, and nifedipine possess unique pharmacologic mechanisms of action, each drug produced a statistically significant improvement in flap survival. The results of this study suggest that topical drug therapy may play an important role in clinical salvage of the failing skin flap. Further studies are needed to explore the potential of combination drug therapy.

Use of a nitric oxide precursor to protect pig myocutaneous flaps from ischemia-reperfusion injury

Nitric oxide is a radical with vasodilating properties that protects tissues from neutrophil-mediated ischemia-reperfusion injury in the heart and intestine. Previous studies in our laboratory suggested that L-arginine, a nitric oxide precursor, can protect skin flaps from ischemia-reperfusion injury. In this study, we examined the effects of L-arginine on the survival of myocutaneous flaps in a large animal model and established whether this effect was mediated by nitric oxide and neutrophils. Two superiorly based 15 x 7.5 cm epigastric myocutaneous island flaps were dissected in 15 Yorkshire pigs weighing 45 to 50 kg. One of the flaps was subjected to 6 hours of arterial ischemia and then reperfused for 4 hours (ischemia-reperfusion flaps), whereas the other flap was used as a non-ischemic control (non-ischemia-reperfusion flaps). The flaps were divided into four groups: control non-ischemia-reperfusion flaps that received only saline (group I); ischemia-reperfusion flaps that were treated with saline (group II); and flaps treated with either L-arginine (group III) or Nomega-nitro-L-arginine methylester (L-NAME), a nitric oxide synthase competitive inhibitor, plus L-arginine in equimolar amounts (group IV). These drugs were administered as an intravenous bolus 10 minutes before the onset of reperfusion, followed by a 1-hour continuous intravenous infusion. Full-thickness muscle biopsies were taken at baseline, 3 and 6 hours of ischemia, and 1 and 4 hours of reperfusion. The biopsies were evaluated by counting neutrophils and measuring myelo-peroxidase activity. At the end of the experiment, skeletal muscle necrosis was quantified using the nitroblue tetrazolium staining technique, and a full-thickness biopsy of each flap was used for determination of water content. Statistical analysis was performed using analysis of variance and the Newman-Keuls test. Non-ischemia-reperfusion flaps showed no muscle necrosis. Ischemia-reperfusion flaps treated with saline had 68.7 +/- 9.1 percent necrosis, which was reduced to 21.9 +/- 13.6 percent with L-arginine (p < 0.05). L-NAME administered concomitantly with L-arginine demonstrated a necrosis rate similar to that of saline-treated ischemia-reperfusion flaps (61.0 +/- 17.6 percent). Neutrophil counts and myeloperoxidase activity after 4 hours of reperfusion were significantly higher in ischemia-reperfusion flaps treated with L-NAME and L-arginine as compared with the other three groups (p < 0.05). Flap water content increased significantly in ischemia-reperfusion flaps treated with saline and L-NAME plus L-arginine versus non-ischemia-reperfusion flaps (p < 0.02) and L-arginine-treated ischemia-reperfusion flaps (p < 0.05). There was no difference in flap water content between ischemia-reperfusion flaps treated with L-arginine and non-ischemia-reperfusion flaps. Administration of L-arginine before and during the initial hour of reperfusion significantly reduced the extent of flap necrosis, neutrophil accumulation, and edema due to ischemia-reperfusion injury in a large animal model. This protective effect is completely negated by the use of the nitric oxide synthase blocker L-NAME. The mechanism of action seems to be related to nitric oxide-mediated suppression of ischemia-reperfusion injury through neutrophil activity inhibition.

Ischemic preconditioning improves the survival of skin and myocutaneous flaps in a rat model

Inadequate blood supply of pedicle flaps results in partial necrosis, and prolonged ischemia during free-tissue transfer can result in partial or complete flap necrosis. Recent research in the field of cardiovascular surgery has shown that ischemic preconditioning (repeated brief episodes of coronary artery occlusion followed by reperfusion) improves myocardial muscle survival when the heart is subsequently subjected to prolonged ischemia. Preconditioning of skin or myocutaneous flaps as either pedicle or free flap models has never been studied. The goal of this investigation was to measure the effect of ischemic preconditioning on myocutaneous and skin flap survival areas and total necrosis rates after variable periods of global ischemia. In 220 rats, 100 transverse rectus abdominis myocutaneous flaps and 120 dorsal cutaneous flaps were randomized into treatment and control groups. The treatment flaps underwent preconditioning by three cycles of 10 minutes of pedicle clamping followed by 10 minutes of reperfusion for a total preconditioning period of 1 hour. The control flaps were perfused without clamping for 1 hour. Both control and treatment flaps then underwent global ischemia for 0, 2, 4, 6, 10, or 14 hours by pedicle clamping. Flap survival area was measured on the fifth postoperative day. Statistical analysis was performed with analysis of variance, student's t tests, and probit analysis. Preconditioning improved survival areas of pedicle myocutaneous flaps (0-hour group) from 47 +/- 16 percent (mean percent area surviving +/- SD) to 63 +/- 5 percent. This difference was statistically significant (t test, p < 0.04). There was no statistically significant improvement in pedicle skin flap survival. For free flap models (flaps undergoing global ischemia), preconditioning increased the survival areas of skin and myocutaneous flaps (analysis of variance, p < 10(-5)). For the skin flap model, statistical significance of the survival area difference was reached at 6, 10, and 14 hours of ischemia (t test, p < 10(-4)). The magnitude of this effect was higher in the myocutaneous flap model and reached statistical significance at 2, 4, 6, and 10 hours of ischemia (p < 10(-3)). Preconditioned flap survival areas were increased by two to five times that of non-preconditioned flaps at these ischemia times. Preconditioning lowered total necrosis rates at all ischemia times for both flap models. The critical ischemia time when 50 percent of skin flaps became totally necrotic (CIT50) improved from 6.9 to 12.4 hours by preconditioning. Similarly, preconditioning improved the CIT50 of myocutaneous flaps from 3.6 to 9.2 hours. For the first time, statistically significant improvements of partial necrosis areas and total necrosis rates have been demonstrated through intraoperative ischemic preconditioning of skin and myocutaneous flaps. In clinical practice, application of this technique may lead to improved survival during pedicled or free transfer of myocutaneous flaps and free transfer of skin flaps.

Monoclonal antibody to intercellular adhesion molecule 1 protects skin flaps against ischemia-reperfusion injury: an experimental study in rats

The purpose of this study was to evaluate the blockage of polymorphonuclear neutrophil endothelial adhesion by using a monoclonal antibody to the intercellular adhesion molecule 1 (ICAM-1) ligand to prevent ischemia-reperfusion injury in rat skin flaps. A skin and subcutaneous tissue flap (3.0 cm x 4.5 cm) supplied by the superficial epigastric artery and vein including the femoral vessels was isolated unilaterally in 45 male Sprague-Dawley rats and clamped for 9 hours (groups II and III) or 12 hours (groups IV and V) of ischemia. Five animals in group I were sham-operated only with 5 minutes of ischemia. Animals in groups II (n = 10) and IV (n = 10) received 0.05 mg of monoclonal antibody to ICAM-1 (0.20 mg/kg) in 0.5 ml of 0.9% normal saline intravenously 15 minutes before reperfusion; those in groups III (n = 10) and V (n = 10) received 0.5 ml of normal saline. The flaps were assessed histologically, by measuring viable and nonviable areas, and by diffuse reflectance spectroscopy to determine the ratio of oxyhemoglobin to deoxyhemoglobin. Flap measurements revealed that the average area of flap survival was 90.6 +/- 12.8 percent in group II and 18.3 +/- 19.6 percent in the control group (III) (p < 0.002). In the animals subjected to 12 hours of ischemia, those treated with monoclonal antibody to ICAM-1 (group IV) were 57.1 +/- 23.1 percent viable, which was significantly greater than the control animals (group V), in which only 0.3 +/- 1.0 percent of the flap was viable. Analysis of the diffuse reflectance spectra showed a hyperemic response during the first 10 minutes after reperfusion in animals treated with monoclonal antibody to ICAM-1. In group III, however, the spectra demonstrated a decreased amount of oxyhemoglobin, indicating decreased reperfusion of the flap after ischemia when compared with group II. Histopathologically, few inflammatory changes could be observed in groups I, II, and the viable areas of group IV. Marked damage was observed in groups III and V. We concluded that treating ischemic skin flaps with monoclonal antibody to ICAM-1 was effective for alleviating reperfusion injury after 9 or 12 hours of warm ischemia. The reactive hyperemic response determined by diffuse reflectance spectroscopy in groups II and IV correlated with areas of flap survival. Antibodies to particular adhesion molecules, such as ICAM-1, have potential clinical utility in that they could be administered, individually or together, to patients immediately before reestablishing perfusion after free-tissue transfer or replantation to block the adverse effects attributed to reperfusion injury.

The effects of L-arginine and iloprost on the viability of random skin flaps in rats

The effects of an intravenous infusion of L-arginine as a physiological precursor of endothelium-derived relaxing factor/nitric oxide (EDRF/NO), iloprost (a stable prostacyclin (PGI2) analogue), and L-arginine combined with iloprost on skin viability were studied in 9 x 3 cm random pattern skin flaps in rats. Intravenous infusion of all drugs was started at the beginning of the operation and continued for 60 minutes. At the end of infusion period the depth of fluorescein dye penetration in the skin flap was assessed visually from photographic records, and the flap survival area was measured by the grid method at the seventh postoperative day. There was a significant reduction in distal necrosis of random skin flaps after intravenous infusion of L-arginine, iloprost, and L-arginine combined with iloprost (p < 0.01). Possible mechanisms that may be responsible for impairment of endothelium-dependent vasodilation and vasospasm in the microvasculature of random skin flap and their prevention with L-arginine and iloprost include restoration of the depleted stores of NO which in turn causes vasodilatation and has an antithrombotic effect.

Amrinone, a selective phosphodiesterase III inhibitor, improves microcirculation and flap survival: a comparative study with prostaglandin E1

BACKGROUND

Amrinone, a selective phosphodiesterase (PDE) III inhibitor, is a newly developed agent that possesses a combination of positive inotropic and vasodilating properties as a result of preventing the degradation of cAMP and it has recently been licensed for treatment of heart failure alone. Amrinone is expected to be useful for the treatment not only of heart failure but also of peripheral circulatory disorders, including vascular disease, and for ischemic flaps, because it improves microcirculatory hemodynamics. To investigate potential therapeutic applications of amrinone, we evaluated its ability to improve microcirculatory hemodynamics and flap survival.

MATERIALS AND METHODS

The rat skinfold chamber technique was employed to quantify microcirculation directly in vivo. The improved survival area of random flaps in rats treated with amrinone was examined to assess therapeutic efficacy of this drug. Its effects were compared with those of prostaglandin E1 (PGE1), which has been widely approved as an agent for improving hemodynamics.

RESULTS

Microcirculatory blood flow and flap survival area were significantly increased in both amrinone- and PGE1-treated animals, compared to the saline-treated controls. The ameliorating effects of amrinone were comparable to those of PGE1.

CONCLUSIONS

The results of this study suggest amrinone to be a potentially useful drug not only for treating heart failure but also for improving microcirculation in patients with vascular diseases and for postoperative care after reconstructive surgery.

Correlation of neutrophil activation and skin flap survival in pharmacologically altered pigs

In inflamed tissue, neutrophils produce tissue necrosis factors such as free oxygen radicals. We investigated the role of neutrophils in random flap survival using the tissue neutrophil marker myeloperoxidase (MPO), an in whole blood using flow cytometry with the neutrophil activation marker 2'7'dichlorofluorescein diacetate. Hypopigmented pigs were treated with the experimental 21-aminosteroid lipid antioxidant U-74389G (oxygen free radical scavenger) before dorsal random skin flaps were elevated. Extent of flap survival was measured by surface planimetry 7 days after surgery. Mean flap survival was 64.1% +/- 3.4% in the 3-mg/kg-treated group, and 68.0% +/- 3.4% in the 1-mg/kg-treated group-both significantly greater than the survival in vehicle-treated controls (48.6% +/- 2.3%). We measured MPO in tissue extracts using an enzyme-linked immunoassay, which showed less MPO in treated animals than in controls. Flow cytometry results were nonspecific. These data suggest that U-74389G improves random skin flap viability by inhibiting neutrophil infiltration into the flap.

Timing, magnitude, and utility of surgical delay in the TRAM flap: I. Animal studies

Surgical delay is an effective technique, but the precise timing of the delay effect and the required extent of the delay procedure are uncertain. We endeavored to study flap survival as a function of the duration of the delay period in a rat transverse rectus abdominis myocutaneous (TRAM) flap model. Two specific delay procedures (limited and extensive) were utilized, and flap survival was assessed after delay periods of 3, 7, 10, 14, 21, and 30 days (n > or = 7, all groups). A delay of 7 days or greater resulted in statistically significant improvement in flap survival in all groups. The delay effect appeared to be maximal at 14 days, and in the extensive delay group, a 14-day delay resulted in statistically greater flap survival than a 7-day delay. Improvement in flap survival was greater when an extensive delay procedure was used. Although the model system has limitations, the rat TRAM flap appears to be a suitable model for the study of the delay phenomenon. Possible clinical correlations are addressed in part II.

Survival of normothermic microvascular flaps after prolonged secondary ischemia: effects of hyperbaric oxygen

Although hyperbaric oxygen has been shown to improve the survival rate of ischemic grafts and flaps of many types, it has not been studied extensively in free tissue transfer. This study was designed to evaluate the effect of hyperbaric oxygen on flap survival when exposed to critical combinations of primary ischemia, reperfusion, and secondary ischemia times. Unilateral abdominal adipocutaneous island flaps based on the superficial inferior epigastric vessels were raised in 133 Sprague-Dawley rats. Primary normothermic ischemia was induced by applying a microvascular clamp to the vascular pedicle for 6 hours. The clamp was removed for 2 hours of reperfusion and then reapplied for a 6-, 10-, or 14-hour period of secondary ischemia. After completion of the secondary ischemia time, the clamp was removed, and the animals were randomly assigned to one of three treatment regimens. The control animals breathed normobaric air, and the others breathed normobaric 100% oxygen or hyperbaric oxygen (100% oxygen at the equivalent of 33 feet of seawater, 2.0 atmospheres absolute), respectively, for two periods of 90 minutes for 7 days. Flap survival was assessed at postoperative day 7 and was found to be an all-or-none phenomenon. Maximum likelihood-derived survival curves were fitted to the data and used to calculate the secondary ischemic time at which 50% of the flaps survived (D50). The D50 for the air and 100% oxygen groups was 6 hours, whereas that for the hyperbaric oxygen group was 10 hours. This difference in D50 was found to be statistically significant (analysis of variance, p < 0.05). Chi-squared statistical evaluation of pooled data reaffirmed a statistically significant increase in flap survival of the animals treated with hyperbaric oxygen vs. those treated with air or 100% oxygen (p < 0.03 and p < 0.01, respectively). Hyperbaric oxygen enhances the tolerance of normothermic, microvascular flaps to prolonged secondary ischemia. A similar effect was not noted in the 100% oxygen group; therefore the additional expense and technology of a hyperbaric chamber system is necessary to achieve this effect.

Failure of buflomedil to improve wound healing in ischaemic skin flaps

The effect of buflomedil and isoxsuprine on the healing of ischaemic wounds was investigated using an ischaemic flap model previously evaluated on rats. The drugs were given twice daily intraperitoneally for a total of nine days starting on the day before operation. The wounds were tested biomechanically after 10 and 20 days of healing, respectively, and the length of surface necrosis on the flaps was measured after 10 days. The study showed no differences in any of the biomechanical (functional) parameters of the ischaemic wounds compared with the control groups, either after 10 or 20 days of healing. There were no differences in the length of surface necrosis on the flaps. Neither of these drugs has so far convincingly proved to be effective in the treatment of ischaemic wounds or flaps.

Use of the Guinea Pig Flank Flap in Skin Flap Research

A variety of flaps in laboratory animals have been designed that propose to parallel the behavior of human skin under different experimental conditions. In the search for a readily available and affordable island skin flap model that combines reliable anatomy with a pedicle of substantial size, we have designed in the guinea pig a cutaneous flap based on the superficial circumflex iliac artery and vein. In 22 adult female Hartley guinea pigs, an 8 × 4 cm flank flap based on the superficial circumflex iliac pedicle was raised, and its characteristics were evaluated for applications to skin flap research. Dermofluorometric studies were performed that confirm the vascularity of this flap, and 100% survival of the flap was seen 5 days after surgery in all animals. Of particular benefit was the demonstration that both afferent and efferent blood samples can be taken from the pedicle directly, which allows for the direct quantification of plasma markers after physiologic insults to the skin flap, such as burn or ischemia. This anatomically reliable and easily dissected flap lends itself well to preliminary skin flap research and may contribute to standardization of a model for further studies examining the behavior of skin microcirculation under adverse physiologic conditions.

The effects of extended perioperative pentoxifylline on random skin flap survival

PURPOSE

This study was designed to determine the effects of long-term perioperative pentoxifylline administration on random skin flap survival in an appropriate animal model. A secondary objective was to document bioavailability of pentoxifylline in the animal model by measuring blood levels of parent compound and metabolites at regular intervals and comparing these to levels measured in humans.

MATERIALS AND METHODS

A randomized control study of the effects of oral pentoxifylline on the survival of "random" skin flaps was conducted at the animal care facility of an academic tertiary referral center on six randomly selected Yorkshire pigs. Oral pentoxifylline was administered daily to four pigs for 3 months, and two pigs received placebo. Pentoxifylline blood levels for each experimental animal were measured after 4, 8, and 12 weeks of daily dosing. Blood viscosity, fibrinogen, and hematocrit were measured for each of the six animals on day 1, day 30, day 60, and day 91. On day 91, 12 surgical random skin flaps were elevated on each of the six animals and immediately sewn back in the donor bed. Pentoxifylline dosing was continued for 2 weeks, and placebo was continued in control animals. On postoperative day 15, all animals were killed and all flaps were measured individually for area of viability. The outcome measure was the detection of statistically significant increase in survival area in skin flaps of those animals administered perioperative pentoxifylline.

RESULTS

No significant augmentation of flap survival was noted in experimental animals when compared with those in the control group; no significant difference was noted between or within groups of experimental animals. Pentoxifylline and metabolite blood levels in all experimental animals at every interval were noted to be comparable to those documented in human studies; metabolite concentrations conformed to expected patterns as observed in humans. No significant alterations of blood viscosity, fibrinogen, or hematocrit were measured in the experimental animals when compared with those in the control group. The only animal showing mean flap survival outside the 95% confidence interval was one in the control group.

CONCLUSION

No augmentation of random skin flap survival could be shown in the pig model after a 3 month regimen of daily oral pentoxifylline. Blood levels of pentoxifylline in experimental animals were compared with those documented in humans. No alteration of blood viscosity, fibrinogen, or hematocrit was noted in any of the experimental animals when compared with each other or with those in the control group.