Low-level laser irradiation,cyclooxygenase-2 (COX-2) expression and necrosis of random skin flaps in rats

Skin flaps are still a matter of concern among surgeons, as failures can occur leading to flap necrosis. However, low-level laser irradiation has been reported as an effective tool to improve the viability of ischemic flaps, yet its mechanisms of action remain unclear. We investigated the effect of low-level laser irradiation on the viability of random skin flaps in rats and determined COX-2 expression in the flap pedicle. The study animals comprised 24 EPM-1 Wistar rats which were randomly allocated into three equal groups. A cranially based dorsal random skin flap measuring 10 × 4 cm was created in all the animals. In one group, laser irradiation was simulated (sham group), and in the other two groups the animals were irradiated at 12 points with 0.29 J at 20 mW (energy density 10.36 J/cm², irradiance 0.71 W/cm²), or with 7.3 J at 100 mW (energy density 260.7 J/cm², irradiance 3.57 W/cm²). These procedures were applied to the cranial half of the flap immediately after surgery and were repeated on days 2 and 5 after surgery. The percentage necrotic area was determined on day 7 after surgery by the paper template method. The immunohistochemical expression of COX-2 in the samples was given scores from 0 to 3. The necrotic area was smaller in group irradiated at 7.3 J compared to sham-treated group and to the group irradiated at 0.29 J (P < 0.05); there was no difference between the sham-treated group and group irradiated at 0.29 J. COX-2 expression was lower in the group irradiated at 7.3 J than in the sham-treated group and the group irradiated at 0.29 J (P < 0.001). Low-level laser therapy was effective in decreasing random skin flap necrosis in rats using a laser energy of 7.30 J per point. Laser irradiation also decreased the expression of COX-2 in the flap pedicle.     

Preconditioning of the distal portion of a rat random-pattern skin flap.

It has been shown that preconditioning either by proximal pedicle clamping or by pedicle intravascular drug administration, for example with adenosine, can improve flap survival. These methods, however, are not well suited to random-pattern flap transfer in the clinical setting. The aim of this study was to evaluate clinically applicable preconditioning methods for random-pattern flaps. Eighteen male Sprague-Dawley rats were used. Bipedicled dorsal skin flaps (2 x 8cm) containing panniculus carnosus were elevated. In the ischaemic preconditioning group the cranial pedicle was clamped for 20min, followed by 40min reperfusion before the cranial pedicle was cut, producing a caudally based random-pattern flap. In the pharmacologic preconditioning group adenosine was locally injected in the cranial half of the flap before the cranial pedicle was cut. In the control group saline was locally injected instead of adenosine and the pedicle was cut in the same manner. Flap survival area was evaluated at day 7. Flap survival area in both preconditioning groups was significantly higher than in the control group (P<0.05). Both preconditioning methods can improve random-pattern flap survival in rats. These methods may prove useful in the clinical setting.     

The effect of ischemic preconditioning on secondary ischemia in skin flaps

Ischemic preconditioning is a useful manipulation to reduce the undesirable effects of ischemia. The beneficial results of this phenomenon against ischemia-reperfusion have been seen in different flap models; however, all these studies have focused on primary ischemia. In this study, we investigated the effects of ischemic preconditioning on secondary ischemia in a skin flap model. We used the 6- x 3-cm-sized epigastric skin flap in 40 Wistar rats. In all animals, primary global ischemia of 2 hours was followed by 4 hours of either arterial or venous secondary ischemia 24 hours after the primary ischemia and ischemic preconditioning (IP) was tested in this protocol. Ischemic preconditioning was performed by 2 cycles of 15 minutes of repeated ischemia/reperfusion periods. The animals were allocated into 4 groups: group 1 (n = 10 animals): primary ischemia (2 hours) + secondary arterial ischemia (4 hours); group 2 (n = 10 animals): IP + primary ischemia (2 hours) + secondary arterial ischemia (4 hours); group 3 (n = 10 animals): primary ischemia (2 hours) + secondary venous ischemia (4 hours); group 4 (n = 10 animals): IP + primary ischemia (2 hours) + secondary venous ischemia (4 hours). Flap viability was assessed 1 week after the surgical procedure, and surviving flap area was recorded as a percentage of the whole flap area. Group 1 was compared with group 2, and group 3 was compared with group 4 to evaluate the effects of ischemic preconditioning against secondary arterial and venous ischemia. t test and Mann-Whitney rank sum tests were used for statistical analysis. There were statistical differences both between groups 1 and 2 and groups 3 and 4. The results revealed that ischemic preconditioning was an effective procedure to reduce the flap necrosis as a cause of secondary ischemia in skin flaps.     

Heat shock preconditioning reduces ischemic tissue necrosis by heat shock protein (HSP)-32-mediated improvement of the microcirculation rather than induction of ischemic tolerance

INTRODUCTION: Supraphysiologic stress induces a heat shock response, which may exert protection against ischemic necrosis. Herein we analyzed in vivo whether the induction of heat shock protein (HSP) 32 improves survival of chronically ischemic myocutaneous tissue, and whether this is based on amelioration of microvascular perfusion or induction of ischemic tolerance. METHODS: The dorsal skin of mice was subjected to local heat preconditioning (n = 8) 24 hours before surgery. In additional heat-preconditioned animals (n = 8), HSP-32 was inhibited by tin-protoporphyrin-IX. Unconditioned animals served as controls (n = 8). A random-pattern myocutaneous flap was elevated in the back of the animals and fixed into a dorsal skinfold chamber. The microcirculation, edema formation, apoptotic cell death, and tissue necrosis were analyzed over a 10-day period using intravital fluorescence microscopy. RESULTS: HSP-32 protein expression was observed only in heat-preconditioned but not in unconditioned flaps. Heat preconditioning induced arteriolar dilation, which was associated with a significant improvement of both arteriolar blood flow and capillary perfusion in the distal part of the flap. Further, heat shock reduced interstitial edema formation, attenuated apoptotic cell death, and almost completely abrogated the development of flap necrosis (4% +/- 1% versus controls: 53% +/- 5%; P[r] < 0.001). Most strikingly, inhibition of HSP-32 by tin-protoporphyrin-IX completely blunted the preconditioning-induced improvement of microcirculation and resulted in manifestation of 72% +/- 4% necrosis. CONCLUSION: Local heat preconditioning of myocutaneous tissue markedly increases flap survival by maintaining adequate nutritive perfusion rather than inducing ischemic tolerance. The protection is caused by the increased arteriolar blood flow due to significant arteriolar dilation, which is mediated through the carbon monoxide-associated vasoactive properties of HSP-32.     

Depletion of glutathione by buthionine sulfoximine decreases random-pattern skin flap viability in rats

BACKGROUND: Glutathione (GSH) is one of the most highly concentrated intracellular antioxidants. Exogenous GSH has been shown to increase random-pattern skin flap survival. However, the effects of endogenous GSH depletion on random-pattern skin flap viability have never been studied. MATERIALS AND METHODS: To evaluate the effects of systemic glutathione depletion on random-pattern skin flap survival in rats, 28 Wistar albino rats were divided into control, sham, and BSO (buthionine sulfoximide, a selective inhibitor for gamma-glutamylcysteine synthetase) groups. Dorsal, cranial-based random-pattern skin-flaps were elevated and the percentage of flap necrosis was measured in all rats at the postoperative day 7. RESULTS: BSO-treated rats showed increased skin flap necrosis when compared with untreated animals (P < 0.001). High-dose BSO treatment group had more clinically evident necrosis than low dose group (P < 0.05). CONCLUSIONS: This study reveals the importance of endogenous GSH for random skin-flap viability.     

Influence of low-level laser therapy on wound healing in nicotine-treated animals

Low-level laser therapy (LLLT) has been shown to have several biological effects that favor the healing process, and nicotine has been shown to delay the healing process. In this study we investigated the healing of open wounds created on the back of rats treated with nicotine with or without LLLT. Of 115 animals, 59 received subcutaneous injections of saline solution, and the others received subcutaneous injections of nicotine (3 mg/kg body weight), twice a day throughout the study period. After 30 days, skin wounds were created on the back of the animals. The animals receiving saline injections were divided into two groups: group 1 (G1, n = 29), in which the wounds were left untreated, and group 2 (G2, n = 30), in which the wounds were treated with LLLT (GaAlAs, 660 nm, 30 mW, 5.57 J/cm² per point, 0.39 J, 13 s per point, 0.42 W/cm²). The animals receiving nicotine injections were also divided into two groups: group 3 (G3, n = 29), in which the wounds were left untreated, and group 4 (G4, n = 27), in which the wounds were treated with LLLT. The animals were killed 3, 7 or 14 days after surgery. Wound healing was evaluated histologically both qualitatively and semiquantitatively. Wounds of G2 showed a delay in epithelial migration and connective tissue organization compared to those of G1. Wounds of G2 showed faster healing than those of G1; similarly, wounds of G4 showed more advanced healing than those of G3. LLLT acted as a biostimulatory coadjuvant agent balancing the undesirable effects of nicotine on wound tissue healing.     

The effect of parenteral pentoxifylline therapy on skin flap survival

Summary The effect of pentoxifylline as a hemorrheologic agent on skin flap survival has been observed. A caudally pedicled dorsal flap with an ischemic component in rats was used as the model. The flap survival was calculated to be 0.807±0.049 in the control group (n = 15), where flap survival was found to be 0.9713±0.018 in the pentoxifylline treated group (n = 15) (t = 12.19, p < 0.005). In the meantime, living flap length was measured as 9.96±0.72 in the control group, and 11.84±0.18 in the pentoxifylline treated group. With these results, we have come to the conclusion that parenteral pentoxifylline therapy is effective on ischemic skin flap survival in the rat model. Correspondence to: M. Topalan, MD     

Remote ischemic preconditioning modulates p38 MAP kinase in rat adipocutaneous flaps

Ischemic preconditioning has been shown to improve survival of cutaneous flaps. The authors examined the effect of remote ischemic preconditioning (RIPC) on phosphorylation of p38 MAP kinase and related the results to flap survival. Female Wistar rats had 8 x 12-cm abdominal adipocutaneous flaps raised on the medial branch of the superficial epigastric artery. Controls (Group 1) had the flap elevated and the pedicle clamped for 3 hr, then closed with a sheet of plastic between the flap and abdominal wall. Group 2 animals had RIPC by tourniquet on the contralateral hind limb before the flap was dissected. Group 3 animals mimicked Group 2 and also had an infusion of the nitric oxide blocker, N-nitro-L-arginine methyl ester (L-NAME) 5 min prior to the RIPC. Group 4 had the flap elevated prior to the RIPC. All groups except Group 1 had 10 min of RIPC with 30 min of reperfusion, then 3 hr of ischemia. Tissue samples were taken at the distal margins of the flaps before preconditioning and 30 min after preconditioning for detection of p38 MAP kinase and phosphorylated p38 MAP kinase (pp38 MAP kinase). Group 2 flaps (RIPC before flap elevation) exhibited better flap tissue survival and had well-defined phosphorylation of p38 MAP kinase 30 min post RIPC, when compared to the other groups. Pre-infusion with the nitric oxide blocker (Group 3) before RIPC blocked the survival advantage conferred by preconditioning and diminished the phosphorylation of p38 MAP kinase. Tissue from all groups showed very little phosphorylation of p38 MAP kinase following 3 hr of ischemia. Thus, increased tissue survival is correlated with elevated levels of p38 MAP kinase phosphorylation following RIPC. This effect is inhibited by blockade of nitric oxide. Modulation of the p38 MAP kinase pathway may represent a protection pathway for ischemic preconditioning.     

Effects of diode laser therapy on blood flow in axial pattern flaps in the rat model

. Axial pattern skin flaps are a very important reparative tool for the plastic and reconstructive surgeon in the reconstruction of tissue defects. From whatever unfortunate reason, part or all of such flaps occasionally suffers from irreversible ischaemia with loss of the flap. Infrared diode laser therapy has been shown to improve local and systemic circulation. The present study was designed to assess the effect of an 830 nm diode laser (power density, 18.5 W/cm², energy density 185 J/cm²) on the blood flow of axial pattern flaps in the rat model and their survival, compared with unirradiated controls. The flaps were raised in all animals (n=40), and blood flow assessed with laser speckle flowmetry (LSF). In the experimental groups (3 groups, n=10 per group), the flaps were irradiated either directly over the dominant feeder vessel (iliolumbar artery), at the proximal end or at the distal end of the flap itself and blood flow assessed during irradiation. Flowmetry was performed again in all animals at 5 and 10 min postirradiation, and the flaps sutured back in position. The unirradiated controls were handled in exactly the same way, but the laser was not activated. The survival rate of the flaps was assessed on the fifth postoperative day. LSF demonstrated significant increased blood flow in the flaps at 5 and 10 min postirradiation in all experimental groups compared with the control animals. At five days postirradiation, there was significantly better survival of the flaps in all the experimental groups compared with the controls (p<0.01), but no significant difference was seen between any of the experimental groups. We conclude that laser therapy increases the blood flow and perfusion of transferred flaps, and that this has significant effects on the survival of the flaps. One possible mechanism of modulation of the autonomic nervous system is discussed. Paper received 19 March 2001; accepted after revision 28 September 2001.     

Modified pedicled tongue-like skin extension fasciocutaneous flaps for heel reconstruction; a versatile technique

Soft-tissue reconstruction for isolated heel defects represents a challenging surgical dilemma due to tight inelastic tissue and inevitable acute angulations of the fibro-vascular pedicle of local flaps. A modified pedicled flap with a tongue-like skin extension has been designed to eliminate tunnel tightness to avoid traction injury and kinking of the blood vessel. Between 2003 and 2005, eight patients with isolated heel defects were analysed (six men, two women). Their age ranged from 5 to 47 years (median age = 31). Six were traumatic while two were neuropathic. Reversed sural (n = 4), medial planter (n = 3) and one dorsalis pedis artery fasciocutaneous flap were used. The average follow-up period was 1 year during which the flaps were monitored for venous congestion, ischemia, superficial epidermolysis and partial or total flap loss. Only one modified pedicle flap showed mild venous congestion; on the other hand, no other ischemic events such as superficial epidermolysis or flap loss were experienced. The modified tongue-like process extension is considered a valuable tool to increase the versatility of these flaps.     

缺血预处理后热休克蛋白对皮瓣成活的影响及作用机理

目的 探索提高皮瓣成活率有有效方法和途径。方法 采用大鼠背部轴型皮瓣，制成活体原位缺血预处理模型，观察缺血预处理对超长跨区供血皮瓣成活率的影响及热休克蛋白70的表达。结果 缺血预处理后即刻断蒂组（A组）和缺血预处理后24h断蒂组（B组）皮瓣平均存活面积明显高于对照组，A组和B组的皮瓣平均存活面积差异无显著性意义；A组和B组中免疫组化染色可见大量阳性表达，对照组免疫组化染色仅见微量弱阳性表达。结论 缺血预处理能提高超长跨区供血皮瓣的存活率, 其机理可能与缺血预处理后热休克蛋白合成增加所引发的机体自身的保护作用有关。     

Pharmacologic preconditioning of random-pattern skin flap in rats using local cyclosporine and FK-506: interaction with nitric oxide system

It has been suggested that immunophilin ligands such as cyclosporine and FK-506 (tacrolimus) affect the survival of ischemic tissues. Our objective was to show an acute effect of local cyclosporin-A (CsA) and FK-506 on ischemic protection in a random-pattern skin-flap model in rats and investigate the effect of nitric oxide (NO) pathways as a modulator of protection of these agents.Ninety male Sprague-Dawley rats were randomly assigned to treatment groups. Bipedicled dorsal flaps (2 x 8 cm) were elevated at midline. Prior to cutting the cranial pedicle to induce permanent ischemia, pharmacologic preconditioning groups received local injection of CsA (0.3, 1, or 3 nmol/flap) or FK-506 (0.01, 0.03, or 0.1 pmol/flap), and the ischemic preconditioning (IPC) group underwent temporary clamping of the cranial pedicle. At the seventh day postoperatively, the survival of the flaps was measured. In other groups, nitric oxide synthase inhibitor N omega-nitro-l-arginine methyl ester hydrochloride (L-NAME) was administered with effective CsA and FK-506, and ischemic preconditioning. Nitric oxide precursor L-arginine doses were also studied, and a systemic subeffective dose (100 mg/kg) was coadministered with subeffective CsA and FK-506.Significant increase in flap survival was obtained with CsA (1 nmol/flap), FK-506 (0.1 pmol/flap), and IPC. These protections were abolished by systemic administration of L-NAME (10 mg/kg). Coadministration of subeffective doses of CsA (0.3 nmol/flap) and FK-506 (0.03 pmol/flap), with subeffective systemic l-arginine, significantly improved flap survival.Pharmacologic preconditioning with local, single, low doses of CsA or FK-506 is shown to be even more effective than IPC. Administration of the NOS substrate l-arginine potentiates these effects.     

ATP-sensitive potassium channels mediate the anti-ischemic properties of ischemic and pharmacologic preconditioning in rat random-pattern skin flap

Ischemic preconditioning (IPC) and pharmacologic preconditioning by morphine and adenosine may significantly decrease the amount of necrosis in rat random pattern skin flaps. We examined the role of ATP-sensitive potassium channels (K(ATP) channels) in mediating these protective phenomenon by using glibenclamide a nonspecific blocker of these channels. We also investigated whether administration of diazoxide an opener of the K(ATP) channels could mimic the same protective effect. Ninety male Sprague-Dawley rats were randomly divided into either control or treatment groups (n = 6 each). Bipedicled dorsal skin flaps (2 x 8 cm) were elevated at the midline. In pharmacologic preconditioning groups, 1 mL of morphine (5 mg/flap), adenosine (0.5 mg/flap), or different doses of diazoxide (0.5, 1, 5, and 15 mg/flap) were administered locally in the cranial half of the flap, respectively. One milliliter of saline was locally injected in the control group. In the IPC group, 1 hour after local saline injection the cranial pedicle was clamped for 20 minutes, and then 40 minutes' reperfusion was performed. In another experiment, 0.3 mg/kg of glibenclamide was injected intraperitoneally 30 minutes before local administration of saline or drug in ischemic or pharmacologic preconditioning groups. Regardless of the group, all flaps were cut at the cranial side 2 hours after elevation and were sutured back. Flap survival area was evaluated on the seventh postoperative day. IPC and pharmacologic preconditioning with morphine, adenosine, and diazoxide (in higher doses; 1, 5, and 15 mg/flap) improved survival area compared with the control group. Glibenclamide abolished their protective effect. K(ATP) channels may have a key role in anti-ischemic properties of IPC and pharmacologic preconditioning.     

Metformin improves skin flap survival through nitric oxide system

Background

Metformin has shown cardioprotective effects in experimental models of ischemia reperfusion, which is partially mediated through nitric oxide (NO) synthesis. We investigated the effects of metformin pretreatment in a rat model of random-pattern skin flap, and the probable role of NO system.

Materials and methods

In the first experiment, the rats received increasing doses of metformin (150, 200, and 300 mg/kg), 4 h before the procedure. Dorsal skin flaps with caudal pedicles were elevated at the midline and flap survival was measured 7 d after surgery. Pathologic review of the skin flap specimen was performed in a subset of animals. In the second experiment, for evaluation of the role of NO, an NO synthase inhibitor N-nitro-L-arginine methyl ester hydrochloride (L-NAME) was administered with and without the effective dose of metformin. In the next experiment, subtherapeutic dose of NO precursor, L-Arginine, was administered with and without subeffective dose of metformin.

Results

Metformin pretreatment at doses of 200 and 300 mg/kg significantly increased skin flap survival rate. However, administration of L-NAME abolished the protective effects of metformin. On the other hand, subtherapeutic dose of L-arginine augmented the effects of low-dose metformin and significantly increased skin flap survival. Skin flaps from those rats that received 300 mg/kg metformin pretreatment and those treated with subtherapeutic doses of L-arginine and metformin showed increased vasodilation compared with control group.

Conclusions

Metformin pretreatment can improve skin flap survival through an NO dependent pathway.     

Effect of Human Placental Extract Treatment on Random-Pattern Skin Flap Survival in Rats

Background: Human placental extract (HPE), prepared from the placentas of healthy, postpartum females, displays various physiological activities, including antioxidative properties. In this study, a dorsal skin flap model was used to investigate the effect of HPE on flap viability in rats. Materials and methods: Forty male Sprague-Dawley rats underwent random-pattern skin flap surgeries. The animals were randomly divided among a control group and three treatment groups (localized injection (LI), 10 mg/kg/d localized HPE injections; low-dose treatment (LT), 10 mg/kg/d systemic HPE injections; high-dose treatment (HT), 40 mg/kg/d systemic HPE injections). Surviving skin flap areas were measured 7 days after surgery and tissue samples were stained with hematoxylin and eosin; vascular endothelial growth factor expression was determined immunohistochemically. To evaluate the antioxidant and antiapoptotic effects of HPE, malondialdehyde, glutathione peroxidase, and caspase-3 levels were examined. Results: Seven days after surgery, HPE-treated animals had significantly reduced necrotic areas, rats receiving the highest HPE dose demonstrated the greatest flap survival. In the HPE groups, the histopathological scores were lower than for the control group. Immunohistochemistry showed markedly more numerous vascular endothelial growth factor-positive cells in the HT group than in the C group. Malondialdehyde levels were significantly lower and glutathione peroxidase levels were higher in the HT group than in the C group. HPE treatment significantly inhibited apoptosis by lowering caspase-3 activity. Conclusions: HPE treatment yielded positive effects on flap survival, due to its antioxidant and antiapoptotic properties. These results suggest a new therapeutic approach for enhancing flap viability and accelerating wound repair.     

Factors associated with hernia and bulge formation at the donor site of the pedicled TRAM flap

The purpose of this study was to evaluate the correlation between risk factors and hernia or bulge formation at the donor site of the transverse rectus abdominis myocutaneous (TRAM) flap. A retrospective study was conducted between September 2005 and December 2008 in 206 patients who underwent breast reconstruction with pedicled TRAM flap. Eight (3.9%) of these patients had abdominal wall hernia and 26 (12.6%) had abdominal bulging. The incidence of hernia was significantly higher (P < 0.05) among patients with body mass index (BMI) ≥ 30 kg/m² (hernia incidence, 15.0%) than that among patients with BMI <30 kg/m² (hernia incidence, 3.2%), while the incidence of abdominal bulge was significantly lower (P < 0.05) among patients with BMI ≥ 30 kg/m² (abdominal bulge incidence, 5.0%) than that among patients with BMI ≥ 30 kg/m² (abdominal bulge incidence, 19.1%). Therefore, obesity was identified as a risk factor for abdominal wall hernia. It was also found that the use of mesh to reinforce the abdominal wall significantly reduced (P < 0.025) the incidence of hernia (use of mesh (hernia incidence, 2.5%) versus non-mesh (hernia incidence, 5.9%)) and abdominal bulge (use of mesh (abdominal bulge incidence, 9.9%) versus non-mesh (abdominal bulge incidence, 17.3%)) among the patients.     

Preconditioning of the rat random-pattern skin flap: modulation by opioids.

Opioid receptors have been implicated in protecting several organ systems from ischaemic events. The authors have studied the effects of opioid receptors on random-pattern skin flap survival. Sixty-nine male Sprague-Dawley rats were used. Bipedicled dorsal skin flaps (2 x 8 cm) were elevated at the midline. Different doses of morphine (0.01, 0.1, 1 and 5 mg/flap) were administered locally in the cranial half of the flap and systemically through intraperitoneal injections (5 and 10 mg/kg). In another experiment, 0.4 mg/flap of naloxone was injected followed by 5 mg/flap injection of morphine to determine whether the effect of morphine is receptor mediated. The role of the opioid receptors in the ischaemic preconditioning (IPC) phenomenon was investigated by administration of naloxone (0.4 mg/flap) 1 h before clamping the cranial pedicle for 20 min followed by 40 min of reperfusion. Appropriate control groups were included. The cranial pedicle was cut 2 h after saline or drug administration in all groups and flap survival area was evaluated on the seventh postoperative day. Local administration of morphine in higher doses (1 and 5 mg/flap) significantly reduced the amount of flap necrosis when compared to that of the control cohort (P < 0.05). Naloxone abolished this protective effect of morphine. Furthermore naloxone significantly decreased the anti-ischaemic effect of the IPC. Systemic administrations of morphine had no significant effect on flap survival area in compare with the control group.     

Value of remote ischaemic preconditioning in rat dorsal skin flaps and clamping time

Objective: According to previous reports, remote ischaemic preconditioning (RIPC) is a “delay” procedure that is highly likely to be useful for preventing skin flap necrosis. Differences in the extent of necrosis in rat dorsal skin flaps when different clamping times were used in RIPC were compared among the four groups described below.

Methods: Group A was a control group in which no prior ischaemic area was created, and both back legs were devascularised for 15 min in Group B, 30 min in Group C, and 60 min in Group D. The experiments were performed on 10 rats in each group, and the surviving area was measured. One-way analysis of variance (ANOVA) and Tukey’s multiple comparison test were used for analysis, with p?<?0.05 regarded as significant.

Results: The surviving area of the skin flap was 15.4?±?1.8?cm² in Group A, 15.4?±?2.0?cm² in Group B, 17.9?±?2.0?cm² in Group C, and 19.2?±?3.4?cm² in Group D, with significant differences between Groups A and D and between Groups B and D.

Conclusions: RIPC consisting of 60 min of ischaemic preconditioning may be clinically useful as a method of preventing skin flap necrosis.     

Peritoneal membrane recruitment in rats: a micro-computerized tomography (μCT) study

The peritoneal contact surface area (PCSA), which represents the area parameter in the mass transfer area coefficient (MTAC), is a crucial marker in the evaluation of peritoneal dialysis effectiveness. However, the capacity to recruit a larger PCSA has only been rarely demonstrated in vivo and, in most cases, changes in MTAC are interpreted as permeability changes and not as surface area variations. Here, we report the use of micro-computerized tomography (μCT) for the measurement of PCSA changes to various fill volumes. Using this three-dimensional imaging method, PCSA was measured in vivo in 26 healthy Wistar rats receiving intraperitoneally increasing fill volumes of peritoneal dialysis solutions: 5 mL (group 1, n = 8), 10 mL (group 2, n = 8) and 15 mL (group 3, n = 10) per 100 g of body weight. A non-ionic iodinated contrast agent was added to the dialysis solution in order to distinguish the intraperitoneal dialysis solutions from soft tissues. The normalized PCSA/weight ratio (cm²/g) increased with fill volume: 1.12 ± 0.10 cm²/g (range 0.98–1.25) in group 1; 1.74 ± 0.08 cm²/g (range 1.64–1.87) in group 2; 2.13 ± 0.09 cm²/g(range 1.90–2.30) in group 3. With this μCT method, PCSA recruited in vivo with a 10 mL/100 g fill volume was in the range 94–107%) of ex vivo total peritoneal surface area (evPSA), as calculated with the Kuzlan’s formula. With a 15 mL/100 g fill volume, the in vivo-measured PCSA, the exchange surface area, surpassed the evPSA (range 113–139%).