Improve Skin Flap Survival Research Articles

Improved skin flap survival after local heat preconditioning in pigs 1

Background Preconditioning induces the expression of heat shock proteins (HSPs), which can help a cell survive an acute episode of stress. Similar to the induction of HSP expression, the cell protection is independent of the type of stress. The aim of this study was to test in a large, randomized animal model, if skin flap survival may be improved by local heat preconditioning and induction of HSP 70. Materials and methods Twenty-four hours before surgery, a heating blanket was laid on the buttocks of large white pigs. In the preconditioned group ( n = 6), the blanket was warmed up to 43°C for 3 × 30 min, whereas it was kept at room temperature in between the heating episodes as well as in the control animals ( n = 6). A random pattern skin flap was raised on both sides of the buttocks. Flap survival was measured clinically. Induction of HSP and apoptosis were assessed quantitatively by immunohistochemistry and TUNEL assay, respectively. Results Preconditioning reduced flap necrosis from 40 ± 8% of the total flap surface to 7 ± 14% ( P < 0.01). Induction of HSP was significantly higher in the experimental group (79 ± 12% versus 42 ± 13%, P < 0.01), whereas apoptosis in healthy flap tissue was reduced from 30 ± 11 to 11 ± 6 cells/visual field ( P < 0.01). Conclusion In the present study, necrosis and apoptosis rate of skin flaps could be reduced significantly due to local heat preconditioning. Our results suggest that ischemia-related wound healing complications could be diminished with local heat application, a most simple and least invasive method of preconditioning.

Heparin protects against skin flap necrosis: relationship to neutrophil recruitment and anti-coagulant activity

Heparin has been shown to improve survival of surgical skin flaps. However, it is not known whether the protective effect of heparin is related to its anticoagulative or anti-inflammatory effects. Surgical flaps were raised in the dorsal skin of Sprague-Dawley rats. Neutrophil recruitment was determined by measuring the tissue content of myeloperoxidase (MPO) and clotting time was estimated by assessment of activated partial thromboplastin time (APTT) in plasma. Administration of heparin (150 U/kg) significantly increased skin flap survival from 44% in vehicle-treated controls to 91%. This heparin treatment increased APTT by 4.5 fold. However, administration of 150 U/kg of heparin had no effect on skin flap neutrophil recruitment. In contrast, we found that the polysaccharide fucoidan reduced MPO and also improved skin flap survival. In conclusion, we demonstrate that protective effect of clinically relevant doses of heparin correlates with its ability to prolong clotting time and not to inhibition of neutrophil accumulation in the healing of skin flaps.

Efficacy of postoperative steroids on ischemic skin flap survival in rats

Necrosis of skin flaps remains a significant clinical problem. This study examined whether steroids improve skin flap survival in rats. Random skin flaps were raised in 30 male Sprague-Dawley rats. Intramuscular methylprednisolone (n=15) or saline solution (n=15) were administered 1, 24, and 48 h after flap elevation. Surviving flap areas were measured after 7 days. The mean surviving flap area in the methylprednisolone group was greater than that in controls (916 vs. 675 mm). These results suggest that postoperative methylprednisolone improves skin flap viability in the ischemic rat flap model.

Heat shock protein and high-dose aspirin: effects on random skin flap survival in a rat model.

The heat shock response is known to have a protective effect against flap ischemia. It has been shown that heat shock protein (hsp) expression can be augmented in vivo with the administration of high-dose aspirin before heat treatment. The authors hypothesized that administration of aspirin before hsp induction through heat stress would enhance further the protective effects of the heat shock response against skin flap ischemia. They used a random dorsal skin flap model in 32 rats divided into four groups (N = 8 each): control, heat shock, aspirin plus heat shock, and aspirin. Before surgery, rats in the two heat shock groups were placed in a 45 degrees C water bath until core body temperature measured 42 degrees C, and they were maintained at 42 degrees C for 15 minutes. Rats in the two aspirin groups received a single oral dose of aspirin (100 mg per kilogram) 1 hour before heat bath or surgery. Immunohistochemistry confirmed hsp expression in the two heat groups. Skin flap survival was improved significantly (p < 0.05) in the heat shock (55%), aspirin plus heat shock (58%), and aspirin (60%) groups when compared with controls (45%). Contrary to their hypothesis, aspirin combined with hsp induction did not offer greater protection from ischemia than hsp induction alone (p > 0.05). However, high-dose aspirin administration alone did improve skin flap survival when compared with controls. Future studies are needed to investigate further the role of pharmacological therapy combined with hsp induction in improving skin flap survival and to delineate the dose-response relationship between aspirin and hsp.

Delivery of FGF-2 but not VEGF by encapsulated genetically engineered myoblasts improves survival and vascularization in a model of acute skin flap ischemia.

Stimulating angiogenesis by gene transfer approaches offers the hope of treating tissue ischemia which is untreatable by currently practiced techniques of vessel grafting and bypass surgery. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) are potent angiogenic molecules, making them ideal candidates for novel gene transfer protocols designed to promote new blood vessel growth. In this study, an ex vivo gene therapy approach utilizing cell encapsulation was employed to deliver VEGF and FGF-2 in a continuous and localized manner. C(2)C(12) myoblasts were genetically engineered to secrete VEGF(121), VEGF(165) and FGF-2. These cell lines were encapsulated in hollow microporous polymer membranes for transplantation in vivo. Therapeutic efficacy was evaluated in a model of acute skin flap ischemia. Capsules were positioned under the distal, ischemic region of the flap. Control flaps showed 50% necrosis at 1 week. Capsules releasing either form of VEGF had no effect on flap survival, but induced a modest increase in distal vascular supply. Delivery of FGF-2 significantly improved flap survival, reducing necrosis to 34.2% (P < 0.001). Flap vascularization was significantly increased by FGF-2 (P < 0.01), with numerous vessels, many of which had a large lumen diameter, growing in the proximity of the implanted capsules. These results demonstrate that FGF-2, delivered from encapsulated cells, is more efficacious than either VEGF(121) or VEGF(165) in treating acute skin ischemia and improving skin flap survival. Furthermore, these data attest to the applicability of cell encapsulation for the delivery of angiogenic factors for the treatment and prevention of tissue ischemia.

Nonsurgical delay of cutaneous flaps using the flashlamp pumped pulsed dye laser.

The surgical delay procedure is an effective method for improving skin flap survival. However, it has many disadvantages, such as bleeding, infection, and pain. It also requires an additional operation and a long time for wound management. Nonsurgical delay has a great importance, but pharmacological efforts for delay phenomena have never found clinical application. In this study, the authors attempted to reproduce the delay phenomena via the flashlamp pumped dye laser. Forty Sprague-Dawley rats were studied in four groups of 10 rats each. The experimental and control flaps were on the same rat. Flaps were planned on the ventral skin of the rats, and were symmetrical, three sided, based caudally, and were 2 cm in width, extended to the measured midpoint between the xiphoid and the sternal notch. The laser was applied to the different areas of the experimental flaps 15 days before flap elevation. A week later flap survival was determined by overlaying millimeter-grid acetate paper. Full-surface and perimeter "lased" experimental flaps showed a marked increase in surviving areas when compared with the control flaps. This kind of flap delay has a great potential in clinic application.

Calcitonin gene-related peptide improves skin flap survival and tissue inflammation.

The effects of systemic administration of calcitonin gene-related peptide (CGRP) on survival and inflammation of experimental skin flaps subjected to prolonged arterial ischemia were studied. An island groin flap was elevated in the rat. The femoral artery was occluded for 8, 10, 12 or 14 h in four groups of 10 rats. In a group of 10 sham-operated control animals, the femoral artery was not occluded. After ischemia, blood flow was restored and flap survival evaluated at day 7. Following 12 h of ischemia, three flaps (30%) survived, compared with 100% survival of the control group. In the second part of the study the effects of CGRP on flap survival were assessed. Eighty flaps were rendered ischemic for 12 h, and received systemic CGRP (10(-7), 10(-8), 10(-9), 10(-10) M) or saline (control) at the end of the ischemia period. Administration of CGRP (10(-7) M) significantly increased the number of flaps surviving compared with the control. The effect of systemic pretreatment of the animals with the CGRP receptor antagonist CGRP8(-37), followed by CGRP (10(-7) M) treatment was also evaluated in 10 flaps. Flap survival in this group was 10%. In the third part of the study the anti-inflammatory effects of CGRP were evaluated. Forty rats were subjected to arterial ischemia for 12 h, and received systemic CGRP (10(-7) M), or saline at the end of the period of ischemia. The animals were sacrificed at 24 h and flap tissue samples were obtained. Myeloperoxidase (MPO) analysis was used as marker of neutrophil accumulation. CGRP (10(-7) M) significantly reduced the 24 h MPO accumulation in the flap, compared with saline treatment. A group of animals was pretreated with CGRP8(-37), followed by CGRP (10(-7) M), and a significant increase of MPO accumulation was seen, compared with the group treated only with CGRP. This study suggests that CGRP has a beneficial effect on survival of the rat ischemic groin flap, and diminishes the inflammatory response to the ischemic insult.

The use of P31 magnetic resonance spectroscopy to evaluate the effect of ATP-MgCl2 perfusion on the metabolism of rat skin island flaps.

Depleted levels of adenosine triphosphate (ATP) are described as one of the important causes of skin flap failure. This study evaluated the beneficial effects of intra-arterial perfusion of ATP-magnesium chloride (MgCl2) in ischemic neurovascular skin island flaps in the rat and observed the changes of the highenergy phosphate metabolite using phosphorus 31-(P31) magnetic resonance spectroscopy (MRS). The changes of ATP, phosphocreatine (PCr), and inorganic phosphate (Pi) were observed from P31 MRS and the ratios of each metabolite were compared. The extent of skin flap survival was assessed 7 days after operation using an image analyzer. The PCr/Pi ratio of the experimental group (ATP-MgCl2) was significantly different from the control group (balanced salt solution; p < 0.05). Furthermore, the infusion of ATP-MgCl2 (40.3%) significantly improved the area of flap survival compared to the control group (14.2%; p < 0.05). The ratios of PCr/Pi PCr/(PCr + Pi) correlated with the extent of flap survival, and correlation coefficients were 0.59 and 0.60, respectively. In conclusion, ATP-MgCl2 improved skin flap survival. We were able to assess the metabolic state of the ATP-MgCl2-perfused skin flap and found that PCr/Pi ratios correlated with flap survival.

Use of the Tunable Dye Laser to Delay McFarlane Skin Flaps

To determine whether the argon tunable dye laser, used in a noncutting, hemocoagulative mode, improves skin flap survival as effectively as a surgical delay procedure. A physiologic, controlled trial was completed with three groups: acute control skin flaps, surgical delay skin flaps, and experimental laser delay skin flaps. The outcome variable was percentage of skin flap survival. Forty-four male Sprague-Dawley rats. McFarlane skin flaps were raised in all groups. The first group had no delay procedure, the second had the standard surgical delay, and the third group was lased at the periphery of the flap 2 weeks before raising the acute flap. The acute control group had survival of 85.7% +/- 1.5% (mean +/- SE) of skin flaps; surgical control group, 94.4% +/- 0.7%; laser delay group, 96.5% +/- 0.1%. The survival of the experimental group was better than the acute control group and was not different from the surgical delay group by the Scheffé multiple comparison test. This research may lead to a technique to reproduce the benefits of the delay phenomenon without the risks and cost of a surgical procedure.

Comparison of tunable dye and KTP lasers in nonsurgical delay of cutaneous flaps

PROBLEM: Reproducing the benefits of the delay phenomenon without the risks and cost of a surgical procedure has long been a goal of skin flap physiologists. After the success of the suture-delay technique and argon tunable dye laser in improving survival in McFarlane skin flaps, important questions remained: (1) will laser delay be effective in dermal flaps, (2) can induction of collateral blood flow be documented, and (3) is the KTP laser, which is generally more available to otolaryngologists, more effective than the argon tunable dye laser. METHODS: The KTP and argon tunable dye lasers were compared by use of the laser-delay technique, with two outcome measures—blood flow and survival. The laser-delay procedure was accomplished with the laser in a noncutting mode in an attempt to coagulate cutaneous vessels at the periphery of a planned skin flap. The objective was to induce collateralization and improve skin flap survival. Patterns of blood flow were tested by use of the base occlusion test. Flap survival of an acute control flap group was compared with that of the laser delay groups. RESULTS: Blood flowing to the distal flap area originated from the base of the flap area after laser delay. Flap survival of the laser delay groups was significantly improved over that of the control group. CONCLUSION: Both lasers were able to effectively induce collateralization and improve flap survival. (OTOLARYNGOL HEAD NECK SURG 1995;113:92-8.)

Perfusion imaging of skin island flap blood flow by a scanning laser-Doppler technique

Conventional laser-Doppler perfusion measurements can only obtain information from a single site. Since superficial blood flow is heterogeneous, this is a serious limitation, particularly in studies of methods to improve skin flap survival. A scanning laser-Doppler instrument has been developed which provides both an image and quantitative information about perfusion of the superficial tissue. We have evaluated this instrument in a circumflex iliac artery island flap model in the pig. The validity of the model was demonstrated by fluorescein dye injection and histology. Elevation of flaps was found to increase proximal flap blood flow but to decrease it in the distal portion. In flaps subjected to arterial ischaemia (9 h) and reperfusion we found an early increase in proximal flow, which gradually extended distally over the first 40 to 60 min. 16 h later, flow had declined, compatible with reperfusion damage to the vasculature. We suggest that perfusion imaging may be a valuable technique for investigating the mechanisms and extent of

The effect of nifedipine on skin flap survival in rats.

Maintaining the viability of an extended skin flap remains one of the continuing challenges in reconstructive surgery. As flaps lengthen, viability becomes more unpredictable and necrosis of distal segments can occur. The specific mechanisms involved in determining flap survival remain unclear, but vasoconstriction within the flap microcirculation appears to play a significant role in regulating flap viability. Vasodilators have been used, with limited success, in an attempt to improve survival of ischemic skin flaps in rats. One such agent, nifedipine, a calcium channel blocker, demonstrated conflicting results when used to improve rat skin flap survival, despite its potent vasodilating properties. A standard rat flap model was used to help clarify the potential of nifedipine to salvage ischemic skin flaps. Alterations in flap perfusion were assessed using a laser Doppler flowmeter and dermofluorometry in an attempt to characterize nifedipine's mechanism of action on flap preservation. Increased flap survival was demonstrated in treatment animals when compared to controls. Despite significant improvement in flap viability, perfusion measurements failed to confirm increased flow within the flap microcirculation. Although the mechanisms of action remain speculative, nifedipine may have important therapeutic potential in improving skin flap survival in a clinical setting.

Effects of combined cold and hyperbaric oxygen storage on free flap survival

We have previously reported that hyberbaric oxygen (HBO) improved the survival rate of experimental free flaps. The purpose of this study was to evaluate the effects of combined hypothermia and HBO administered during storage on free flaps and on the xanthine oxidase system in rats. Epigastric skin flaps were stored cold for 48 and 72 hours either in room air or under HBO (2.9 atmospheres absolute, 100% oxygen) before free flap transfer. The success rates of free flaps were 80% (8/10) after 48 hours and 20% (2/10) after 72 hours of cold storage in room air. HBO produced no effect after 48 hours but significantly increased the success rate to 70% (7/10) after 72 hours of cold storage. Tissue hypoxanthine (plus xanthine) levels increased to 210% of normal after 48 hours of cold storage in room air and to 176% in HBO. Elevated hypoxanthine levels returned toward normal by 72 hours of cold storage in room air, while the increased levels remained under HBO. Xanthine oxidase activities significantly increased by 60 to 80% during 72 hours of room air storage. HBO treatment inhibited xanthine oxidase activity to 48% of normal by 72 hours of storage. Free flaps exhibited no significant alterations in GR and G6PDH activity after 48 hours of cold storage in room air or HBO. After 72 hours of cold storage, the room air control displayed a trend of decreasing GR activity and a significant 20% decrease in G6PDH activity, while HBO groups showed no significant alterations in both GR and G6PDH activity compared to normal. Protection of the antioxidative enzymes by hypothermia and inhibition of the xanthine oxidase activity by HBO appear to be one of the mechanisms of improved skin flap survival in free flaps.

Nitric oxide synthase inhibitors improve skin flap survival in the rat.

The ability of nitric oxide (NO) synthase inhibitors to reduce ischemia-induced skin flap necrosis was assessed using a modified McFarlane flap in the rat. Flap survival was significantly improved in L-NIO treated (86 +/- 2%), L-NAME-treated (84 +/- 2%), and aminoguanidine-treated (76 +/- 2%) animals compared to the saline-treated group (54 +/- 2%), P < 0.005. Inhibition of NO synthase significantly decreased the hyperemia and edema within the flaps at 24 hours post-elevation. These findings suggest that endogenous NO production contributes to ischemic necrosis and that inhibition of NO synthase may prove useful in extending survival of tissues subjected to ischemia.

Amelioration of secondary ischaemic injury by perfusion with University of Wisconsin (UW) solution in rat skin flaps

This study was designed to observe the effect of perfusion with University of Wisconsin (UW) preservation solution on skin flap survival following secondary ischaemia caused by venous obstruction in rats. An epigastric flap model was used. Saline-perfused flaps exhibited no significant improvement in survival compared to untreated animals (NS). Skin flaps perfused with UW solution, however, had a significant increase in survival to 40% (8/20) (p < 0.01) when perfused before the onset of primary ischaemia and 30% (6/20) (p < 0.05) when given before the onset of secondary ischaemia. These results show that UW solution improves skin flap survival, presumably through preservation of the microvasculature.

Improved skin flap survival with nicotinic acid and nicotinamide in rats

Improved skin flap survival with nicotinic acid and nicotinamide in rats

Efficacy of steroids and hyperbaric oxygen on survival of dorsal skin flaps in rats

This study was designed to determine if steroids improved skin flap survival in rats, and if steroids and hyperbaric oxygen (HBO) showed an additive beneficial effect. Cranially based, 3 x 9 cm dorsal skin flaps were raised in 60 adult rats. All animals received either intramuscular methylprednisolone (30 mg/kg) or an equal volume of intramuscular saline solution placebo 24 hours and 1 hour before, and 24 hours and 48 hours after, flap elevation. Treatment for animals receiving HBO was begun within 5 hours after flap elevation. The regimen consisted of two 90-minute treatments of 100% oxygen at 2.4 atm separated by 5-hour intervals or room air per day for 3 consecutive days. The 60 rats were divided equally into four treatment groups, as follows: group A, flap elevation alone (control); group B, flap plus steroids; group C, flap plus HBO; and group D, flap plus steroids plus HBO. Surviving flap length was measured by visual inspection 7 days after flap elevation. The mean surviving flap length for group A was 4.9 cm, for group B it was 6.4 cm, for group C it was 6.7 cm, and for group D it was 6.5 cm. The approximately 30% to 36% improvement in surviving flap length was highly statistically significant (p less than 0.006) when compared with controls. However, no statistically significant difference was found between the three treatment modalities. These findings indicate that in a rat dorsal skin flap model, perioperative steroids improve skin flap viability, and that steroids alone are as efficacious as HBO and as steroids combined with HBO.

Improved skin flap survival with nicotinic acid and nicotinamide in rats

The effects of some components of the coenzyme nicotinamide adenine dinucleotide (NAD) on tissue viability were investigated in acute island skin flaps which were constructed to exceed the blood supply provided by a unilateral pedicle of inferior epigastric vessels. Control flaps undergo significant necrosis. Treatment with nicotinamide or nicotinic acid, precursors of NAD, prior to flap elevation significantly improved the area of viability in the random portion of the flap from 44 ± 9% (mean ± SD) to 67 ± 12 and 65 ± 5%, respectively. Similarly, NAD improved viability to 68 ± 10% ( P < 0.001). Treatment with other components, adenosine diphosphoribose or quinolinic acid, had no effect on flap survival. The results suggest that nicotinic acid and nicotinamide deserve therapeutic consideration with regard to the treatment of ischemia/reperfusion injury in skin.

Deferoxamine Decreases Necrosis in Dorsally Based Pig Skin Flaps

Deferoxamine, a free radical scavenger and iron chelator, has been shown to improve skin flap survival in ischemic flap surgery in rats. The present study investigates the value of deferoxamine in ischemic flap surgery in the porcine model. Four 4 x 12 cm flaps, 3 cm apart and 3 cm from the dorsal midline, were elevated on each of six female pigs, weighing 50 to 60 pounds each. The animals were divided into two test groups. Group 1 received six 1 gm doses of deferoxamine in 4 ml of sterile water intramuscularly every 6 hours preoperatively for five doses, followed by the administration of 1 g every 6 hours for the first 6 days postoperatively. Group 2 received 4 ml of normal saline administered intramuscularly as above. The percentage of flap necrosis was assessed on postoperative day 7 by the weighing paper technique. Group 1 had 17.1% necrosis and group 2 had 33% necrosis (p less than 0.005). Deferoxamine has decreased flap necrosis in the porcine model and may be of use in augmenting the surviving length of flaps in human beings.

A Comparative Analysis of the Ability of Five Classes of Pharmacological Agents to Augment Skin Flap Survival in Various Models and Species: An Attempt to Standardize Skin Flap Research

There is a myriad of research in the pharmacological manipulation of skin flap survival. However, skepticism exists as to whether any of these drugs is clinically useful. We evaluated the efficacy of five categories of agents in improving skin flap survival in five different rat flap models. Diltiazem, isoxsuprine hydrochloride, nitroglycerin, prazosin hydrochloride (two doses), and methyldopa were compared in a double-blind, randomized fashion. Their benefits were assessed in a musculocutaneous flap, axial flap, and three types of random flaps. The "best" drug was determined to be nitroglycerin. Its efficacy was verified in a primate model.