Ischemia/reperfusion injury in microvascular surgery

Does the Anastomosis Recipient Vessel Have an Influence on Free Flap Perfusion in Microvascular Head and Neck Reconstruction-A Retrospective Analysis of 338 Cases with Comparison of Flap Perfusion between Different Arterial and Venous Recipient Vessels in Radial Free Forearm Flaps, Anterolateral Thigh Flaps, and Fibula Free Flaps

Background: Flap perfusion is a prerequisite for microvascular free flap survival and a parameter routinely used for flap monitoring. The aim of this study was to investigate the influence of the anastomosis recipient vessel on flap perfusion. Methods: Flap perfusion was retrospectively analyzed in 338 patients who underwent head and neck reconstruction with microvascular free flaps between 2011 and 2020. The Oxygen-to-see tissue oxygen analysis system measurements for intraoperative and postoperative flap blood flow, hemoglobin concentration, and hemoglobin oxygen saturation at 8 and 2 mm tissue depths were compared between arterial anastomosis recipient vessels (external carotid artery [ECA], facial artery [FAA], lingual artery [LIA], and superior thyroid artery [STA]) and venous anastomosis recipient vessels (internal jugular vein [IJV], combination of IJV and IJV branches, IJV branches, and external jugular vein). Results: The postoperative hemoglobin concentration at 2 mm tissue depth differed significantly between arterial anastomosis recipient vessels (ECA, 41.0 arbitrary units [AU]; FAA, 59.0 AU; LIA, 51.5 AU; STA, 59.0 AU; p = 0.029). This difference did not persist in the multivariable testing (p = 0.342). No other differences in flap blood flow, hemoglobin concentration, or hemoglobin oxygen saturation were observed between the arterial and venous anastomosis recipient vessels (p > 0.05 for all). Conclusions: The arterial and venous recipient vessels used for anastomosis did not influence microvascular free flap perfusion. This underlines the capability of the studied recipient vessels to adequately perfuse free flaps, may explain the observed indifferent flap survival rates between commonly used anastomosis recipient vessels, and implies that the recipient vessel is not a confounding variable for flap monitoring with the Oxygen-to-see tissue oxygen analysis system. Further prospective studies are needed to confirm the findings.

Effect of corticosteroids on ischemia-reperfusion injury of deep inferior epigastric perforator flap after re-exploration for anastomosis thrombosis: A prospective randomized trial

Patients undergoing breast reconstruction with the deep inferior epigastric perforator (DIEP) flap are at risk of arterial and venous thrombosis, necessitating flap salvage surgery. However, this carries the risk of ischemia-reperfusion injury (IRI) and potential significant partial or complete flap loss. The objective of this study was to evaluate the potential benefit of corticosteroids in reducing IRI related complications in DIEP flaps that are returned to the operation theater for attempted salvage after venous or arterial failure. A double-blinded prospective randomized study was conducted between January 2012 and January 2023 on patients scheduled for secondary unilateral breast reconstruction using the DIEP flap technique. Patients were included if they developed post-operative venous or arterial flap thrombosis and experienced DIEP flap IRI following operative take-back and anastomosis revision. The treatment group (TG) received a 5-day course of corticosteroids, while the control group (CG) did not receive any specific treatment. Forty-six patients were enrolled in the study. In the CG, two cases of total flap loss and eight cases of partial flap necrosis were observed, while the TG had only 1 case of partial flap necrosis (p < 0.05). The complete resolution of clinical signs of IRI occurred within 13 ± 2.1 days for the TG and 21 ± 3.5 days for the CG (p = 0.00001). The TG had a significantly shorter hospital stay (11.13 ± 0.38 days) compared with the CG (15.47 ± 1.27 days; p < 0.0001). Targeted corticosteroid therapy following a salvage procedure for vascular thrombosis in DIEP flaps has shown promise as an effective treatment for subsequent IRI. This approach may be considered as a viable option for managing IRI in free flaps. However, further studies involving a larger number of patients are required to substantiate our hypothesis.

Reducing Risks for Local Skin Flap Failure

Local tissue flaps are a fundamental technique in cutaneous reconstruction. Reducing the risk of flap failure is of critical importance. The intrinsic vascularity of a flap is the most important determinant of success. Good surgical techniques, including flap design, delicate tissue handling, and tension-less closure, help reduce the risk of flap compromise. Determining the etiology of compromise, including arterial, venous, hematologic, or infectious, is the first step in salvaging a failing flap. Common causes include pedicle kinking, hematoma, pressure/tension, systemic patient factors, and poor surgical technique. Swift action to restore perfusion or venous outflow through numerous strategies is required.

Effect of operative time on complications associated with free flap reconstruction of the head and neck

OBJECTIVE

To evaluate whether prolonged operative time is negatively associated with post-operative complications and length of stay in patients undergoing microvascular free flap reconstruction for complex head and neck defects.

METHODS

342 consecutive patients undergoing microvascular reconstruction for head and neck defects between 2017-2019 at a single institution were evaluated. Operative outcomes and operative time were compared whilst controlling for patient and treatment related factors.

RESULTS

Mean operative time was 551 min and length of stay was 16.2 days. An 11% increase in the risk of a post-operative complication was observed for every additional hour of operative time (OR 1.11, 95% CI 1.03-1.21, p = 0.011) after adjusting for patient and treatment factors. A cut-off of 9 h yielded a 92% increase in complications on either side of this (OR 1.92, 95% CI 1.18-3.13, p = 0.009). Increased operative time was also associated with increased length of stay and return to theatres, but not medical complications.

CONCLUSION

Prolonged operative time is significantly associated with increased surgical complications, length of stay and return to theatres when performing microvascular reconstructive surgery for head and neck defects.

Therapeutic potential of naringin in improving the survival rate of skin flap: A review

Naringin is the main component of Drynaria. Modern pharmacological studies have shown that naringin has a wide range of pharmacological activities, including antioxidant, anti-inflammatory, anti-apoptotic, anti-ulcer, and anti-osteoporosis effects. Its therapeutic effects have been observed in various clinical models, such as atherosclerosis, cardiovascular diseases, diabetes, neurodegenerative diseases, and rheumatic diseases. This review investigates the pharmacological effects of naringin and the associated mechanisms in improving flap survival. This review will also provide a reference for future rational application of naringin, especially in research to improve flap survival.

Empagliflozin protects against renal ischemia/reperfusion injury in mice

Renal ischemia/reperfusion (I/R) can induce acute kidney injury. Empagliflozin is a newly developed inhibitor of sodium-glucose cotransporter-2 (SGLT2) approved as an antidiabetic medication for patients with type 2 diabetes mellitus. Despite the established cardioprotective functions of empagliflozin, its protective role in renal I/R is unclear. Here, the present study evaluated the renoprotective effects of empagliflozin in a mouse model of renal I/R injury. Male C57/BL6 mice were allocated to sham-operated, I/R, and empagliflozin groups. Kidney pedicles on both sides were clamped for 45 min and were reperfused for 24 h. Empagliflozin (1 mg/kg) was administered to the mice for 2 days preischemia. The GSK-3β inhibitor SB216763 was administered intravenously at the beginning of reperfusion (0.1 mg/kg). Renal function and histological scores were evaluated. The kidneys were taken for immunohistochemical analysis, western blotting and apoptosis measurements. We found that empagliflozin decreased serum levels of creatinine and urea, reduced the average kidney weight-to-tibia length ratio, attenuated tubular damage, reduced renal proinflammatory cytokine expression and inhibited apoptosis in injured kidneys. Furthermore, empagliflozin increased renal glycogen synthase kinase 3β (GSK-3β) phosphorylation post I/R. Pharmacological inhibition of GSK-3β activity mimicked the renal protective effects offered by empagliflozin. In summary, these results support a protective role of empagliflozin against renal I/R injury.

Impact of intraoperative ischemia time on acute complications of head and neck microvascular free tissue transfer: A systematic review and meta-analysis

BACKGROUND

To evaluate the relationship between intraoperative ischemia time with acute microvascular free tissue transfer (MFTT) complications in head and neck reconstruction.

METHODS

A systematic review using PRISMA guidelines was performed. Inclusion encompassed all available studies published and indexed using PubMed, Medline, and Embase. Meta-analyses were performed using the Cochrane Review Manager tool. Methodological Index for Non-Randomized Studies (MINORS), the Revised Cochrane risk-of-bias tool for randomized trials, and the NIH Study Quality Assessment Tool for non-randomized prospective studies.

RESULTS

A total of 430 citations were reviewed. 25 were included in our overall qualitative analysis, and 14 for meta-analysis. When comparing ischemia times for flaps with and without complications, no significant difference was observed (p = 0.98). Additionally, in a separate cohort, no significant effect was realized when correlating ischemia time to overall rates and total complications.

CONCLUSION

Ischemia time was not significantly different between those with and without acute flap complications.

An animal experiment study on the application of indocyanine green angiography in the harvest of multi-angiosome perforator flap

Background

This study sought to explore the application value of indocyanine green angiography (ICGA) in the harvest of multi-angiosome perforator flap and the effect of low molecular weight heparin (LMWH) on the survival of postoperative flap.

Methods

Twenty-four SD male rats were selected to construct a three-angiosome perforator flap model with the unilateral iliolumbar artery perforator. They were randomly divided into two groups: the control group was injected with indocyanine green (ICG) into the femoral vein during the operation, and the fluorescence signal was collected and quantitatively analyzed using Real-Time Image Guided System to determine the intraoperative fluorescence imaging length. The experimental group was injected subcutaneously with LMWH (400 U/kg) after 0.5 h postoperatively, and the control group was injected with the same amount of normal saline. The injection was repeated at the same time each day from 0 to 7 days postoperatively. After the flap was sutured in situ, ICGA was performed at 0, 1, 3, 5, and 7 days postoperatively to observe the vascular structure of the two groups of flaps. The flap survival length of the control group was counted at 7 days postoperatively, and the correlation between the intraoperative fluorescence imaging length and the survival length at 7 days postoperatively was calculated. The proportion of distal necrosis of the flaps between the two groups was compared at 7 days postoperatively.

Results

The average length of intraoperative fluorescence imaging in the control group was 6.29±0.50 cm, and the survival length of the flap at 7 days postoperatively was 8.24±0.52 cm. The actual survival length was higher than the intraoperative fluorescence imaging length, with a ratio of 1.31±0.08. The difference was statistically significant (P<0.05). At 7 days postoperatively, the flap necrosis ratio of experimental group and control group were 10.92%±1.30% and 19.11%±1.19%, and the flap necrosis ratio of experimental group was lower than that of control group (P<0.001).

Conclusions

ICGA can locate the position of perforator, and can be used to predict and observe the length of distal survival of multi-angiosome perforator flap postoperatively. LMWH can promote the distal survival of flap and reduce flap necrosis.

Preclinical efficacy of stem cell therapy for skin flap: a systematic review and meta-analysis

Background

A skin flap is one of the most critical surgical techniques for the restoration of cutaneous defects. However, the distal necrosis of the skin flap severely restricts the clinical application of flap surgery. As there is no consensus on the treatment methods to prevent distal necrosis of skin flaps, more effective and feasible interventions to prevent skin flaps from necrosis are urgently needed. Stem therapy as a potential method to improve the survival rate of skin flaps is receiving increasing attention.

Methods

This review followed the recommendations from the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statements. Twenty studies with 500 animals were included by searching Web of Science, EMBASE, PubMed, and Cochrane Library databases, up until October 8, 2020. Moreover, the references of the included articles were searched manually to obtain other studies. All analyses were conducted using Review Manager V.5.3 software.

Results

Meta-analysis of all 20 studies demonstrated stem cell treatment has significant effects on reducing necrosis of skin flap compared with the control group (SMD: 3.20, 95% CI 2.47 to 3.93). Besides, subgroup analysis showed differences in the efficacy of stem cells in improving the survival rate of skin flaps in areas of skin flap, cell type, transplant types, and method of administration of stem cells. The meta-analysis also showed that stem cell treatment had a significant effect on increasing blood vessel density (SMD: 2.96, 95% CI 2.21 to 3.72) and increasing the expression of vascular endothelial growth factor (VEGF, SMD: 4.34, 95% CI 2.48 to 6.1).

Conclusions

The preclinical evidence of our systematic review indicate that stem cell-based therapy is effective for promoting early angiogenesis by up regulating VEGF and ultimately improving the survival rate of skin flap. In summary, small area skin flap, the administration method of intra-arterial injection, ASCs and MSCs, and xenogenic stem cells from humans showed more effective for the survival of animal skin flaps. In general, stem cell-based therapy may be a promising method to prevent skin flap necrosis.

microRNAs in liver and kidney ischemia reperfusion injury: insight to improve transplantation outcome

Ischemia reperfusion injury (IRI) is a condition that occurs wherever blood flow and oxygen is reduced or absent, such as trauma, vascular disease, stroke, and solid organ transplantation. This condition can lead to tissue damage, especially during organ transplantation. Under such circumstances, some signaling pathways are activated, leading to up- or down- regulation of several genes such as microRNAs (miRNAs) that might attenuate or ameliorate this status. Therefore, by manipulating miRNAs level, they can be used as a biomarker for early diagnosis of IRI or suggestive to be therapeutic agents in clinical situation in future.

Effect of intravenous lidocaine on ischemia-reperfusion injury in DIEP microsurgical breast reconstruction. A prospective double-blind randomized controlled clinical trial

BACKGROUND

Ischemia-reperfusion injury in free flaps is associated with tissue damage and is one of the main factors causing flap failure in reconstructive microsurgery. The aim of this study is to assess whether any ischemia-reperfusion injury takes place during a microsurgical flap reconstruction as seen through the levels of malondialdehyde (MDA) and superoxide dismutase, biomarkers of oxidative stress, and to analyze the effect of lidocaine in this process.

METHODS

Twenty-four patients operated for immediate breast reconstruction using the Deep Inferior Epigastric Perforator free flap technique were divided into two groups: one group was treated with a lidocaine intravenous perfusion and the other group with a saline perfusion. MDA and superoxide dismutase (SOD) levels were measured at several points before, during, and after surgery.

RESULTS

There was an increase in MDA levels in both groups, but the lidocaine group experienced a decrease during reperfusion. On the other hand, we observed a rise in SOD levels in both groups, but a decrease during reperfusion in the placebo group. However, these differences between groups were not statistically significant.

CONCLUSIONS

The decreased SOD activity and increased MDA content in our research prove a redox imbalance and high reactive oxygen species levels in flaps, indicating that tissues experience ischemia-reperfusion injury during microsurgical reconstruction. Lidocaine may have a protective effect in free flap surgery, but our results were not statistically significant, so further studies will be required.

Effects of Ischemic Preconditioning and C1 Esterase Inhibitor Administration following Ischemia-Reperfusion Injury in a Rat Skin Flap Model

BACKGROUND

 Ischemia-reperfusion (I/R) injury is a serious condition that can affect the success rate of microsurgical reconstructions of ischemic amputated limbs and complex tissue defects requiring free tissue transfers. The purpose of this study was to evaluate the effects of ischemic preconditioning (IPC) and C1 esterase inhibitor (C1-Inh) intravenous administration following I/R injury in a rat skin flap model.

METHODS

 Superficial caudal epigastric skin flaps (3 cm × 7 cm) were performed on 50 Wistar rats that were randomly divided into five groups. Ischemia was not induced in the control group. All other flaps underwent 8 hours of ischemia prior to revascularization: I/R control group (8-hour ischemia), IPC group (preconditioning protocol + 8-hour ischemia), C1-Inh group (8-hour ischemia + C1-Inh), and IPC + C1-Inh group (preconditioning protocol + 8-hour ischemia + C1-Inh). Survival areas were macroscopically assessed after 1 week of surgery, and histopathological and biochemical evaluations were also measured.

RESULTS

 There were no significant differences in flap survival between the treatment groups that were suffering 8 hours of ischemia and the control group. A significant increase in neovascularization and lower edema formation were observed in the IPC group compared with that in the I/R group. Biochemical parameters did not show any significant differences.

CONCLUSION

 Intravenous administration of C1-Inh did not significantly modulate I/R-related damage in this experimental model, but further research is needed. On the other hand, IPC reduces tissue damage and improves neovascularization, confirming its potential protective effects in skin flaps following I/R injury.

Apelin/APJ signaling suppresses the pressure ulcer formation in cutaneous ischemia-reperfusion injury mouse model

Several studies have demonstrated potential roles for apelin/APJ signaling in the regulation of oxidative stress associated with ischemia-reperfusion (I/R) injury in several organs. Objective was to assess the role of apelin/APJ signaling in the development of pressure ulcers (PUs) formation after cutaneous I/R injury in mice. We identified that cutaneous I/R injury increased the expression of apelin in the skin at I/R site. Administration of apelin significantly inhibited the formation of PUs. The reductions of blood vessels, hypoxic area and apoptosis in I/R site were inhibited by apelin injection. Oxidative stress signals in OKD48 mice and the expressions of oxidative stress related genes in the skin were suppressed by apelin injection. H₂O₂-induced intracellular ROS and apoptosis in endothelial cells and fibroblasts were suppressed by apelin in vitro. Furthermore, MM07, biased agonist of APJ, also significantly suppressed the development of PUs after cutaneous I/R, and the inhibitory effect of MM07 on PUs formation was higher than that in apelin. We conclude that apelin/APJ signaling may inhibit cutaneous I/R injury-induced PUs formation by protecting the reduction of vascularity and tissue damage via suppression of oxidative stress. Exogenous application of apelin or MM07 might have therapeutic potentials against the development of PUs.

Dietary Nitrate Protects Against Skin Flap Ischemia-Reperfusion Injury in Rats via Modulation of Antioxidative Action and Reduction of Inflammatory Responses

Dietary nitrate, found abundant in green vegetables, can be absorbed into the blood and be converted to nitric oxide (NO) in the body. Dietary nitrate has been proved to have many positive physiological functions in the body. Here, we evaluated the therapeutic effects of dietary nitrate on skin flap recovery following ischemia reperfusion (IR). Wistar rats were pretreated with nitrate from one week prior to ischemia to the end of reperfusion. It was found that oral administration of nitrate increased serum nitrate and nitrite levels, protected cells from apoptosis, and attenuated flap tissue edema. In the meantime, the oxidative stress marker malondialdehyde was reduced, while the activities of antioxidant enzymes were restored after nitrate treatment. Moreover, the macrophage and neutrophil infiltration in the flap was significantly attenuated by nitrate supplementation, as were the pro-inflammatory cytokines. In sum, we found that oral administration of nitrate can attenuate skin flap IR injury through the regulation of oxidative stress and inflammatory response.

Fat Extract Improves Random Pattern Skin Flap Survival in a Rat Model

BACKGROUND

Adipose tissue and its derivatives, including adipose-derived stem cells, stromal vascular fraction (SVF), and SVF-gel, have been utilized in the treatment of many ischemic disorders. However, the utilization of these products is limited in clinical applications by concerns related to the presence of cells in these derivatives.

OBJECTIVES

This study aimed to isolate a cell-free fat extract (FE) from fat tissue and to evaluate its proangiogenic ability in vitro as well as its protective effects on skin flap survival in vivo.

METHODS

FE was isolated from human fat via a mechanical approach. The concentrations of several growth factors in the FE were determined by enzyme-linked immunosorbent assay. The proangiogenic ability of FE was evaluated utilizing assays of the proliferation, migration, and tube formation in human umbilical vein endothelial cells in vitro. The protective effects of FE on the survival of random pattern skin flaps were investigated by subcutaneous injection into rats.

RESULTS

Enzyme-linked immunosorbent assay results revealed that FE contained proangiogenic growth factors that promoted proliferation, migration, and tube formation in human umbilical vein endothelial cells in vitro. In addition, FE reduced skin flap necrosis and increased survival, as demonstrated by macroscopic measurements and blood flow analysis. Histological analysis revealed that FE treatment increased the capillary density.

CONCLUSIONS

FE is a cell-free, easy-to-prepare, and growth-factor-enriched liquid derived from human adipose tissue that possesses proangiogenic activity and improves skin flap survival by accelerating blood vessel formation. FE may be potentially used for treating ischemic disorders.

Factors Associated with Free Flap Failures in Head and Neck Reconstruction

Objective

To investigate causes of failure of free flap reconstructions in patients undergoing reconstruction of head and neck defects.

Study Design

Case series with chart review.

Setting

Single tertiary care center.

Subjects and Methods

Patients underwent reconstruction between January 2007 and June 2017 (n = 892). Variables included were clinical characteristics, social history, defect site, donor tissue, ischemia time, and postoperative complications. Statistical methods used include univariable and multivariable analysis of failure.

Results

The overall failure rate was 4.8% (n = 43). Intraoperative ischemia time was associated with free flap failures (odds ratio [OR], 1.062; 95% confidence interval [CI], 1.019-1.107; P = .004) for each addition of 5 minutes. Free flaps that required pedicle revision at time of initial surgery were 9 times more likely to fail (OR, 9.953; 95% CI, 3.242-27.732; P < .001). Patients who experienced alcohol withdrawal after free flap placement were 3.7 times more likely to experience flap failure (OR, 3.690; 95% CI, 1.141-10.330; P = .031). Ischemia time remained an independent significant risk factor for failure in nonosteocutaneous free flaps (OR, 1.105; 95% CI, 1.031-1.185). Alcohol withdrawal was associated with free flap failure in osteocutaneous reconstructions (OR, 5.046; 95% CI 1.103-19.805) while hypertension was found to be protective (OR, 0.056; 95% CI, 0.000-0.445).

Conclusion

Prolonged ischemia time, pedicle revision, and alcohol withdrawal were associated with higher rates of flap failure. Employing strategies to minimize ischemic time may have potential to decrease failure rates. Flaps that require pedicle revision and patients with a history of significant alcohol use require closer monitoring.

Ischemia-reperfusion injury in a rat microvascular skin free flap model: A histological, genetic, and blood flow study

Ischemia reperfusion injury is associated with tissue damage and inflammation, and is one of the main factors causing flap failure in reconstructive microsurgery. Although ischemia-reperfusion (I/R) injury is a well-studied aspect of flap survival, its biological mechanisms remain to be elucidated. To better understand the biological processes of ischemia reperfusion injury, and to develop further therapeutic strategies, the main objective of this study was to identify the gene expression pattern and histological changes in an I/R injury animal model. Fourteen rats (n = 7/group) were randomly divided into control or ischemia-reperfusion group (8 hours of ischemia). Microsurgical anastomoses were objectively assessed using transit-time-ultrasound technology. Seven days after surgery, flap survival was evaluated and tissue samples were harvested for anatomopathological and gene-expression analyses.The I/R injury reduced the survival of free flaps and histological analyses revealed a subcutaneous edema together with an inflammatory infiltrate. Interestingly, the Arginase 1 expression level as well as the ratio of Arginase 1/Nitric oxide synthase 2 showed a significant increase in the I/R group. In summary, here we describe a well-characterized I/R animal model that may serve to evaluate therapeutic agents under reproducible and controlled conditions. Moreover, this model could be especially useful for the evaluation of arginase inhibitors and different compounds of potential interest in reconstructive microsurgery.

Botulinum toxin type A induces protective autophagy in human dermal microvascular endothelial cells exposed to an in vitro model of ischemia/reperfusion injury

Botulinum toxin type A (BTXA) has been reported to increase the survival of ischemic skin flaps; however, the exact mechanism underlying this effect remains unclear and needs to be further established. The present study aimed to elucidate whether autophagy caused by BTXA functions as a protection mechanism and to identify the mechanisms of its regulation by BTXA in human dermal microvascular endothelial cells (HDMECs) subjected to hypoxia/reoxygenation (H/R)-induced injury. HDMECs were harvested from the upper eyelid tissues of female blepharoplasty patients. HDMECs were exposed to BTXA treatment for 12 h and then subjected to hypoxia for 8 h, followed by reoxygenation for 24 h. Chloroquine diphosphate salt (CQ) was used as an autophagy inhibitor. H/R led to extreme injury to the HDMECs as indicated by the rise in the apoptosis rate, which was significantly attenuated by BTXA pretreatment. The outcomes demonstrated that H/R caused autophagy, as evidenced by a higher type II/type I ratio of light chain 3 (LC3), increased expression of Beclin-1 and increased autophagosome formation. BTXA enhanced autophagy and attenuated apoptosis in a dose-dependent manner, whereas CQ attenuated the BTXA antiapoptotic effects and inhibited the formation of autophagolysosomes, which caused clustering of the LC3-II in cells. In conclusion, autophagy promoted by BTXA serves as a potential protective effect on ischemia/reperfusion injury.

Alpha Lipoic Acid: A Therapeutic Strategy that Tend to Limit the Action of Free Radicals in Transplantation

Organ replacement is an option to mitigate irreversible organ damage. This procedure has achieved a considerable degree of acceptance. However, several factors significantly limit its effectiveness. Among them, the initial inflammatory graft reaction due to ischemia-reperfusion injury (IRI) has a fundamental influence on the short and long term organ function. The reactive oxygen species (ROS) produced during the IRI actively participates in these adverse events. Therapeutic strategies that tend to limit the action of free radicals could result in beneficial effects in transplantation outcome. Accordingly, the anti-oxidant α-lipoic acid (ALA) have been proved to be protective in several animal experimental models and humans. In a clinical trial, ALA was found to decrease hepatic IRI after hepatic occlusion and resection. Furthermore, the treatment of cadaveric donor and recipient with ALA had a protective effect in the short-term outcome in simultaneous kidney and pancreas transplanted patients. These studies support ALA as a drug to mitigate the damage caused by IRI and reinforce the knowledge about the deleterious consequences of ROS on graft injury in transplantation. The goal of this review is to overview the current knowledge about ROS in transplantation and the use of ALA to mitigate it.

Magnitude of Soft-Tissue Defect as a Predictor of Free Flap Failures: Does Size Matter?

OBJECTIVES

To examine the relationship between the magnitude of soft-tissue defect and the risk of free-flap and limb-salvage complications/failures.

DESIGN

Retrospective cohort.

SETTING

Level I Trauma Center.

PATIENTS

One hundred twelve patients with free tissue transfers between January 2009 and June 2015.

INTERVENTION

A standardized approach using a consistent team of 2 orthopaedic microvascular surgeons was used for each free-flap reconstruction.

MAIN OUTCOME MEASURE

Soft tissue defect size, total or partial flap failure, and unplanned reoperations.

RESULTS

Of 112 free-flap reconstructions, 57 complications occurred in 43-cases (38%) including 5 total flap failures (4.5%), 7 partial flap failures (6%), and 8 early (7%) and 38 delayed complications (33%). There was a significant correlation between the large defect size (≥200 cm) and partial/total flap failure (n = 80, P = 0.023). There was also a significant correlation between large soft tissue defect size and any complication that is, total or partial failure and early or delayed unplanned return to the operating room (n = 80, P = 0.002). Of the flaps used, multivariate analysis revealed that latissimus flaps had higher odds for failure.

CONCLUSIONS

Soft-tissue defect size ≥200 cm can be associated with a higher rate of total or partial flap failure and any complication in acute trauma setting, which may be due to a larger zone of injury, a higher level of difficulty in achieving complete debridement, and a more complex microvascular dissection. Current and future efforts will need to continue to focus on risk stratification for limb salvage efforts because an accurate assessment of risk is important to the patient, health care provider, and the health care system in general.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The rat groin flap model redesigned for evaluating treatment effects on ischemia-reperfusion injury

BACKGROUND

Although there is a wide application of the rat extended groin flap (epigastric skin flap) in studying different clinical issues, inconsistency arises between studies because many parameters of the extended groin flap have not been well defined.

MATERIALS AND METHODS

The flap is based on the superficial inferior epigastric vessels, which give into a lateral and a medial branch distally. Herein, three steps were taken to redesign this model: First, the ventral vascular anatomy was visualized through an imaging study to determine the flap borders. Second, different ischemic durations were induced on five groups of Lewis rats (n = 5 in each group) by clamping the femoral artery; group 1 (sham group) received no ischemic insult after elevation and was immediately repositioned, and groups 2, 3, 4, and 5 received 12-, 14-, 16-, and 18-hour ischemia, respectively. Percentage of necrosis area was measured after 5 days. Third, the redesigned groin flap model was tested with the ischemic postconditioning for validation.

RESULTS

The flap borders were determined such that both branches of the superficial inferior epigastric vessels were always included to ensure blood supply consistency. As the 14-hour ischemia induced the least variation in necrotic area on rats, it was chosen for further studies. In addition, ischemic postconditioning after 14-hr ischemia resulted in significant reduction of necrosis in this model.

CONCLUSIONS

We have redesigned the extended groin flap model with better-defined borders and consistent vascular anatomy. The ischemia duration was calibrated with predictable necrosis pattern and the practicality was demonstrated. With this model, precise assessment of treatment efficacies on ischemia-reperfusion injury could be achieved in future studies.

Hyperbaric Oxygen Inhibits Reperfusion-Induced Neutrophil Polarization and Adhesion Via Plasmin-Mediated VEGF Release

Background:

Ischemia-reperfusion (IR) injury is seen in many settings such as free flap salvage and limb replantation/revascularization. The consequences—partial/total flap loss, functional muscle loss, or amputation—can be devastating. Of the treatment options available for IR injury, hyperbaric oxygen (HBO) is the most beneficial. HBO inhibits neutrophil-endothelial adhesion through interference of CD18 neutrophil polarization in IR, a process mediated by nitric oxide. The purposes of this study were to examine the involvement of vascular endothelial growth factor (VEGF) in the beneficial HBO effect on CD18 polarization and neutrophil adhesion and investigate the effect of plasmin on VEGF expression in skeletal muscle following IR injury.

Methods:

A rat gracilis muscle model of IR injury was used to evaluate the effect of VEGF in IR, with and without HBO, on neutrophil CD18 polarization and adhesion in vivo and ex vivo. Furthermore, we investigated the effects that plasmin has on VEGF expression in gracilis muscle and pulmonary tissue by blocking its activation with alpha-2-antiplasmin.

Results:

HBO treatment following IR injury significantly decreased neutrophil polarization and adhesion ex vivo compared with the IR group. Anti-VEGF reversed the beneficial HBO effect after IR with polarization and adhesion. In vivo adhesion was also increased by anti-VEGF. HBO treatment of IR significantly increased the VEGF protein in both gracilis and pulmonary vasculature. Alpha-2-antiplasmin significantly reversed the HBO-induced increase of VEGF in gracilis muscle.

Conclusions:

These results suggest that HBO inhibits CD18 polarization and neutrophil adhesion in IR injury through a VEGF-mediated pathway involving the extracellular matrix plasminogen system.

Pre-augmentation soft tissue expansion improves scaffold-based vertical bone regeneration - a randomized study in dogs

OBJECTIVE

Soft tissue (ST) dehiscence with graft exposure is a frequent complication of vertical augmentation. Flap dehiscence is caused by failure to achieve tension-free primary wound closure and by the impairment of flap microcirculation due to surgical trauma. Soft tissue expansion (STE) increases ST quality and quantity prior to reconstructive surgery. We hypothesized that flap preconditioning using STE would reduce the incidence of ST complications after bone augmentation and that optimized ST healing would improve the outcome of bone regeneration.

MATERIALS AND METHODS

Self-filling tissue expanders were implanted in mandibular bone defects in ten beagle dogs. After expansion, alloplastic scaffolds were placed for vertical bone augmentation in STE sites and in control sites without STE pre-treatment. ST flap microcirculation was analysed using laser Doppler flowmetry. The incidence of graft exposures was evaluated after 2 weeks. Bone formation was assessed after 2 months, using histomorphometry and immunohistochemistry.

RESULTS

Test sites showed significantly less impairment of perfusion and faster recovery of microcirculation after bone augmentation. Furthermore, no flap dehiscences occurred in STE sites. Bone regeneration was found in both groups; however, significantly greater formation of new bone was detected in test sites with preceding STE.

CONCLUSIONS

Preconditioning using STE improved ST healing and bone formation after vertical augmentation. The combination of STE and the subsequent placement of alloplastic scaffolds may facilitate the reconstruction of severe bone defects.

Protective effect of telomerase-based 16-mer peptide vaccine (GV1001) on inferior epigastric island skin flap survivability in ischaemia-reperfusion injury rat model

BACKGROUND

Ischaemia-reperfusion injury (IRI) results in oxidative damage and a profound inflammatory reaction, leading to cell death. GV 1001 is a telomerase-based 16-mer peptide vaccine developed against cancer. However, it has also been reported to possess antioxidant and anti-inflammatory properties. The aim of this study was to determine if GV 1001 can reduce the negative effects caused by IRI in a rat skin flap model owing to its anti-oxidant and anti-inflammatory properties.

MATERIALS AND METHODS

In order to evaluate the effect of GV 1001, 5 × 5 cm² inferior epigastric artery based island skin flaps were dissected in 39 8-week-old Sprague-Dawley rats weighing 220-270 g. The rats were divided into three groups: (I) non-ischaemic group; (II) IRI with saline; and (III) IRI with 10 mg GV 1001 treatment. Drugs were administered intra-muscularly directly before and after ischaemia. Flap survival area, neutrophil infiltration, cytokine levels (interleukin [IL]-1, IL-6, and tumour necrosis factor-α), malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity were measured. Flap survivability was analysed at 7 days after surgery.

RESULTS

Flap survival area was significantly larger in group III than in group II. Cytokine release level was also significantly lower in group III. Neutrophil infiltration grade, MDA level, and SOD activity slightly decreased in Group III; however, the changes were not statistically significant.

CONCLUSION

These results imply that GV 1001 exerts a protective effect against IRI through antioxidant effects, reducing reactive oxygen species, and suppressing the inflammatory cascade.

Dynamics of early stem cell recruitment in skin flaps subjected to ischemia reperfusion injury

OBJECTIVE

Bone marrow-derived stromal cell (BMSCs) therapy improves survival of skin flaps subject to ischemia/reperfusion (I/R) injury. However, very little is known about the trafficking and distribution of BMSCs in post-ischemic skin tissue following intravenous administration. The aim of this study was to assess the behavior of BMSCs in post-ischemic skin flaps and to compare the magnitude and kinetics of accumulation of BMSCs and leukocytes following I/R.

METHODS

Cutaneous flaps perfused by the inferior epigastric vessels were created in C57Bl6 mice. The flaps were subjected to 3.5h of ischemia followed by reperfusion. Wound healing and vascular perfusion were assessed in 3 groups of mice (sham, I/R, and I/R+BMSCs treatment) on days 3, 5, 7 and 14 post-reperfusion. The kinetics and magnitude of BMSCs and leukocyte recruitment were quantified in additional 2 groups (Sham and I/R) after I/R using intravital fluorescence microscopy at 2 and 4h after the intravenous injection of fluorescently labeled BMSCs.

RESULTS

Wound healing after I/R was significantly enhanced in skin flaps of mice treated with BMSCs, compared to controls. The rolling velocity of BMSCs was higher compared to leukocytes both in control mice (32.4±3.7μm/s vs 24.0±2.2μm/s, p<0.05) and in I/R mice (34.6±3.8μm/s vs 20.2±2.3μm/s, p<0.005). However, the rolling velocity of both cell populations was not altered by I/R. The firm adhesion and transendothelial migration of BMSCs did not differ from the values detected for leukocytes for both control and I/R mice.

CONCLUSIONS

The magnitude and kinetics of BMSCs recruitment in skin flaps subjected to I/R are not significantly different from the responses noted for leukocytes, suggesting that similar mechanisms may be involved in the recruitment of both cell populations following I/R.

The Effect of Activated Protein C on Attenuation of Ischemia-Reperfusion Injury in a Rat Muscle Flap Model

Ischemia-reperfusion injury is often the final and irreversible factor causing flap failure in microsurgery. The salvage of a microsurgical flap with an ischemia-reperfusion injury contributes to the success of microsurgical flap transfers. Activated protein C (APC), a serine protease with anticoagulant and anti-inflammatory activities, has been shown to improve ischemic flap survival. To date, APC has yet to be applied to models of free flap with ischemia-reperfusion injury. In this study, we aimed to investigate the effect of APC on gracilis flap ischemia-reperfusion injury induced by gracilis vessels clamping and reopening. Sixty male Sprague-Dawley rats were randomly divided into 2 groups. After 4 hours of clamping for ischemia, flaps were reperfused and recombinant human APC (25 μg/kg) or saline was injected in the flaps through pedicles. At 0, 1, 4, 18, and 24 hours after injection (n = 6 for each time point), the tissue samples were harvested. The muscle viability at 24 hours in saline group was 54.8% (15.1%), whereas the APC-treated group was 90.0% (4.3%) (P < 0.05). The induced nitric oxide synthase (iNOS) mRNA expression increased with the time after reperfusion, which were 0.93 (0.25) to 2.09 (0.22) in saline group, and 0.197 (0.15) to 0.711 (0.15) in the APC-treated group. iNOS mRNA expression in the APC-treated group was significantly higher than the saline group at 1, 18, and 24 hours (P < 0.05). Numerous inflammatory cells were observed infiltrating and invading the muscle fibers in the saline group more than the APC-treated group. Increased number of polymorphonuclear cells was also noted in the saline group compared with the APC-treated group (P < 0.05). In conclusion, APC treatment can significantly attenuate ischemia-reperfusion injury and increase the survival of the free flap through down-regulating iNOS mRNA expression and reducing the inflammatory cells. Further research is still needed to be done on various mechanisms in which APC is protective to prevent tissue damage.

Organ-Protective Effects of Red Wine Extract, Resveratrol, in Oxidative Stress-Mediated Reperfusion Injury

Resveratrol, a polyphenol extracted from red wine, possesses potential antioxidative and anti-inflammatory effects, including the reduction of free radicals and proinflammatory mediators overproduction, the alteration of the expression of adhesion molecules, and the inhibition of neutrophil function. A growing body of evidence indicates that resveratrol plays an important role in reducing organ damage following ischemia- and hemorrhage-induced reperfusion injury. Such protective phenomenon is reported to be implicated in decreasing the formation and reaction of reactive oxygen species and pro-nflammatory cytokines, as well as the mediation of a variety of intracellular signaling pathways, including the nitric oxide synthase, nicotinamide adenine dinucleotide phosphate oxidase, deacetylase sirtuin 1, mitogen-activated protein kinase, peroxisome proliferator-activated receptor-gamma coactivator 1 alpha, hemeoxygenase-1, and estrogen receptor-related pathways. Reperfusion injury is a complex pathophysiological process that involves multiple factors and pathways. The resveratrol is an effective reactive oxygen species scavenger that exhibits an antioxidative property. In this review, the organ-protective effects of resveratrol in oxidative stress-related reperfusion injury will be discussed.

Protective effect of botulinum toxin A after cutaneous ischemia-reperfusion injury

Botulinum toxin A (BTX-A) blocks the release of acetylcholine vesicles into the synaptic space, and has been clinically used for aesthetic indications, neuromuscular disorders and hyperhidrosis. Several studies have demonstrated that BTX-A enhanced the blood flow and improved ischemia in animal models. Our objective was to assess the effects of BTX-A on cutaneous ischemia-reperfusion (I/R) injuries, mimicking decubitus ulcers. The administration of BTX-A in I/R areas significantly inhibited the formation of decubitus-like ulcer in cutaneous I/R injury mouse model. The number of CD31(+) vessels and αSMA(+) pericytes or myofibroblasts in wounds were significantly increased in the I/R mice treated with BTX-A. The hypoxic area and the number of oxidative stress-associated DNA-damaged cells and apoptotic cells in the I/R sites were reduced by BTX-A administration. In an in vitro assay, BTX-A significantly prevented the oxidant-induced intracellular accumulation of reactive oxygen species (ROS) in vascular endothelial cells. Furthermore, the administration of BTX-A completely suppressed the ulcer formation in an intermittent short-time cutaneous I/R injury model. These results suggest that BTX-A might have protective effects against ulcer formation after cutaneous I/R injury by enhancing angiogenesis and inhibiting hypoxia-induced cellular damage. Exogenous application of BTX-A might have therapeutic potential for cutaneous I/R injuries.

Improvement of microcirculation and wound healing in vertical ridge augmentation after pre-treatment with self-inflating soft tissue expanders - a randomized study in dogs

OBJECTIVES

We investigated the effect of soft tissue expansion (STE) on vertical ridge augmentation with regard to the incidence of wound dehiscences and the impairment of microcirculation in dogs, and the applicability of laser Doppler flowmetry (LDF) to explore the relation between microcirculation and wound healing.

MATERIAL AND METHODS

Bone defects were created on both mandibular sides in ten beagle dogs by extraction of premolars and removal of bone. Six weeks later, self-filling tissue expanders were implanted in randomly assigned test sites. After 5 weeks of expansion, vertical augmentation was carried out in test and control sites using calvarial onlay grafts side by side with granular biphasic calcium phosphate covered with a resorbable polyethylene glycol membrane. Microcirculation was evaluated with laser Doppler flowmetry (LDF). The incidence of wound dehiscences was evaluated after 2 weeks. The validity of LDF to predict dehiscences was evaluated by construction of receiver operating characteristic (ROC) curves.

RESULTS

After augmentation, test sites showed significantly better perfusion than control sites without preceding STE (P = 0.012). Three days after surgery, perfusion was still significantly decreased in control sites (P = 0.005), while microcirculation in test sites had returned to pre-surgical levels. After 2 weeks, healing in test sites was good, whereas eight dehiscences were found in control sites (P = 0.002). ROC curves showed that microcirculation levels immediately after augmentation surgery significantly predicted subsequent wound dehiscences (AUC = 0.799, CI 0.642-0.955, P = 0.006).

CONCLUSIONS

Laser Doppler flowmetry is suitable for evaluation of soft tissue microcirculation after ridge augmentation. STE reduced the impairment of microcirculation caused by vertical ridge augmentation and decreased the incidence of wound dehiscences in the investigated animal model.

Analysis of risk factors associated with microvascular free flap failure using a multi-institutional database

BACKGROUND

There are numerous factors that may contribute to microvascular free flap failure. Although technical issues are dominant factors, patient and clinical characteristics are also contributory. The aim of this study was to investigate non-technical variables associated with microsurgical free flap failure using a multi-institutional dataset.

METHODS

Utilizing the American College of Surgeons' National Surgical Quality Improvement Program (NSQIP) database, we identified all patients who underwent microvascular free tissue transfer from 2005 through 2009. Univariate analysis was performed to determine the association of flap failure with the following factors: age, gender, ethnicity, body mass index, intraoperative transfusion, diabetes, smoking, alcohol, American Society of Anesthesiologists classification, year of operation, operative time, number of flaps, and type of reconstruction. Factors with a significance of P < 0.2 in the univariate analysis were included in the multivariate logistic regression model to identify independent risk factors.

RESULTS

A total of 639 patients underwent microsurgical free flap reconstruction with 778 flaps over the 4-year study period; 139 patients had two free flaps during the same operation. The overall incidence of flap failure was 4.4% (34/778) (95% confidence interval [CI]: 3.0%, 6.2%). Operative time was identified as an independent risk factor for free flap failure. After adjusting for other factors, those whose operative time was equal to or greater than the 75th percentile (625.5 min) were twice as likely to experience flap failure (AOR 2.09; 95% CI: 1.01-4.31; P = 0.045). None of the other risk factors studied were significant contributors.

CONCLUSIONS

In this series, the overall flap loss rate of was 4.4%. Operative time was a significant independent risk factor for flap failure.

Tadalafil significantly reduces ischemia reperfusion injury in skin island flaps

Introduction:

Numerous pharmacological agents have been used to enhance the viability of flaps. Ischemia reperfusion (I/R) injury is an unwanted, sometimes devastating complication in reconstructive microsurgery. Tadalafil, a specific inhibitor of phosphodiesterase type 5 is mainly used for erectile dysfunction, and acts on vascular smooth muscles, platelets and leukocytes. Herein, the protective and therapeutical effect of tadalafil in I/R injury in rat skin flap model is evaluated.

Materials and Methods:

Sixty epigastric island flaps were used to create I/R model in 60 Wistar rats (non-ischemic group, ischemic group, medication group). Biochemical markers including total nitrite, malondialdehyde (MDA) and myeloperoxidase (MPO) were analysed. Necrosis rates were calculated and histopathologic evaluation was carried out.

Results:

MDA, MPO and total nitrite values were found elevated in the ischemic group, however there was an evident drop in the medication group. Histological results revealed that early inflammatory findings (oedema, neutrophil infiltration, necrosis rate) were observed lower with tadalafil administration. Moreover, statistical significance (P < 0.05) was recorded.

Conclusions:

We conclude that tadalafil has beneficial effects on epigastric island flaps against I/R injury.

A novel laser-Doppler flowmetry assisted murine model of acute hindlimb ischemia-reperfusion for free flap research

Suitable and reproducible experimental models of translational research in reconstructive surgery that allow in-vivo investigation of diverse molecular and cellular mechanisms are still limited. To this end we created a novel murine model of acute hindlimb ischemia-reperfusion to mimic a microsurgical free flap procedure. Thirty-six C57BL6 mice (n = 6/group) were assigned to one control and five experimental groups (subject to 6, 12, 96, 120 hours and 14 days of reperfusion, respectively) following 4 hours of complete hindlimb ischemia. Ischemia and reperfusion were monitored using Laser-Doppler Flowmetry. Hindlimb tissue components (skin and muscle) were investigated using histopathology, quantitative immunohistochemistry and immunofluorescence. Despite massive initial tissue damage induced by ischemia-reperfusion injury, the structure of the skin component was restored after 96 hours. During the same time, muscle cells were replaced by young myotubes. In addition, initial neuromuscular dysfunction, edema and swelling resolved by day 4. After two weeks, no functional or neuromuscular deficits were detectable. Furthermore, upregulation of VEGF and tissue infiltration with CD34-positive stem cells led to new capillary formation, which peaked with significantly higher values after two weeks. These data indicate that our model is suitable to investigate cellular and molecular tissue alterations from ischemia-reperfusion such as occur during free flap procedures.

Submucosal implantation of soft tissue expanders does not affect microcirculation

AIM

To investigate the effect of submucosal implantation of self-filling osmotic tissue expanders on mucosal microcirculation.

MATERIAL AND METHODS

In ten beagle dogs, all premolars were extracted on both sides of the mandible. Tooth-supporting bone and excess soft tissue were removed to mimic a severely resorbed edentulous ridge. Six weeks later, tissue expanders with 0.7 ml final volume were implanted into a submucosal pouch at randomly selected test sites, while contralateral sites served as untreated controls. Microcirculation was assessed in perfusion units (PU) before surgery, after local anaesthesia, directly after surgery, and after 1 and 3 days, using Laser Doppler flowmetry.

RESULTS

Local anaesthesia caused a significant decrease of blood flow from baseline (zero) to -6.4 PU (median; Q1 -10.5; Q3 -0.9; P = 0.006); however, no additional significant decrease was recorded after completion of surgery. Blood flow showed significant increases to -3.6 PU (median; Q1 -11.3, Q3 2.1; P = 0.02) and -4.0 PU (median; Q1 -9.2, Q3 1.1; P = 0.013) after 1 and 3 days, respectively, when compared to the measurements obtained after application of local anaesthesia and completion of surgery. Blood flow had returned to unimpaired baseline levels 1 day after surgery (P > 0.05).

CONCLUSIONS

Submucosal implantation of self-filling osmotic tissue expanders results in only momentary disturbance of microcirculation. The minor impairment of perfusion may explain the consistently good outcomes of submucosal implantation of these tissue expanders.

Transfection of nuclear factor-kappaB decoy oligodeoxynucleotide protects against ischemia/reperfusion injury in a rat epigastric flap model

BACKGROUND

Nuclear factor-kappaB (NF-κB) is considered to play an important role in the response to ischemia/reperfusion (I/R) injury in flap surgery. To inhibit NF-κB, synthetic double-stranded oligodeoxynucleotide (ODN) was used as a decoy. The present study aimed to evaluate the suppressive effects of NF-κB against I/R injury of experimental rat flap model.

METHODS

An extended epigastric island flap was raised and ischemia was induced for 3 h. NF-κB decoy ODN (group D) or single-strand ODN (control; group S) was injected via the contralateral artery when the pedicle was clamped. Transfection efficiency was evaluated with fluorescein isothiocyanate (FITC)-labeled ODN. The effects of NF-κB decoy ODN were analyzed in groups D and S, and an untreated group (group N).

RESULTS

FITC-labeled ODN was distributed over the entire flap. Mean survival rate of the flap was significantly higher in group D than in the other groups (group D: 57.9%; group S: 31.1%; group N 31.7%; p < 0.005). Injured muscle fibers, neutrophils and the expression of inducible nitric oxide synthase were significantly lower in group D. A real-time polymerase chain reaction also demonstrated a tendency for suppression of tumor necrosis factor-α, interleukin (IL)-1β and IL-6.

CONCLUSIONS

We show that NF-κB decoy ODN protected against flap necrosis as a result of I/R injury in rats. We also indicate that intra-arterial injection of naked NF-κB decoy ODN is effective for transfection into target organs. Therefore, transfection of NF-κB decoy ODN represents a novel therapeutic strategy for the treatment of flap surgery in I/R injury.

A comparison of the effects of epidural and spinal anesthesia with ischemia-reperfusion injury on the rat transverse rectus abdominis musculocutaneous flap

The purpose of this study is to compare the effects of spinal and epidural anesthesia on a rat transverse rectus abdominus myocutaneous flap ischemia-reperfusion injury model.Forty Sprague-Dawley rats were divided into 4 experimental groups: group I (n = 10), sham group; group II (n = 10), control group; group III (n = 10), epidural group; and group IV (n = 10), spinal group. After the elevation of the transverse rectus abdominus myocutaneous flaps, all groups except for the sham group were subjected to normothermic no-flow ischemia for 4 hours, followed by a reperfusion period of 2 hours. At the end of the reperfusion period, biochemical and histopathological evaluations were performed on tissue samples.Although there was no significant difference concerning the malonyldialdehyde, nitric oxide, and paraoxonase levels in the spinal and epidural groups, the total antioxidant state levels were significantly increased, and the total oxidative stress levels were significantly decreased in the epidural group in comparison to the spinal group. The pathological evaluation showed that findings related to inflammation, nuclear change rates and hyalinization were significantly higher in the spinal group compared with the epidural group.Epidural anesthesia can be considered as a more suitable method that enables a decrease in ischemia-reperfusion injuries in the muscle flaps.

The influence of zoledronic acid and cyclophosphamide on microcirculation regeneration in healing oral mucosal flaps

The use of intravenous nitrogenous bisphosphonates and antineoplastic agents as postoperative adjuvant cancer management strategies may influence the course of oral wound healing by altering tissue vascularisation kinetics. The aim of this study was to investigate if single or combined zoledronic acid (ZOL) and cyclophosphamide (CTX) would influence microcirculation regeneration in healing oral mucosal flaps. Twenty female specific-pathogen free New Zealand white rabbits were randomised into four groups. In all animals a mucosal flap was raised; three groups were treated each separately with intravenous infusions of 0.14mg/kg ZOL, 100mg/kg CTX, or both, respectively. The fourth group was used as a control. Capillary density measurements, expressed as the mean number of capillaries±SD per mm(2) (cpll/mm(2)), was performed preoperatively using sidestream dark-field (SDF) imaging and repeated immediately postoperatively and on days 2, 4, 7, 9, 11, 14, and 21. Whole blood count and body weight was assessed in each group to monitor pharmacotherapeutic responses. Preoperative mean capillary density was 74±8cpll/mm(2) and 40±11cpll/mm(2) directly after surgery (P<0.0001). Post hoc comparisons of follow-up SDF measurements on days 9-21 between control and ZOL vs. CTX and ZOL+CTX were statistically significant (P<0.05). The present study demonstrates that ZOL did not alter capillary regeneration in healing mucosal flaps. However, although the early healing phase is generally characterised by rapid progression of capillary regeneration, interventions with CTX and ZOL+CTX significantly altered capillary regeneration and persisted beyond the third postoperative week.

Preventing negative effects of smoking on microarterial anastomosis

Although microsurgery has rapid expanded, problems related to microarterial anastomosis continue. Cigarette smoking is one of the major risks for anastomosis by increasing platelet adhesion, and its effects on endothelial cells. Aim of this article is to study the negative effects of cigarettes on microarterial anastomosis line, and to investigate the protective effects of recombinant human erythropoietin (rHuEPO).Ninety-six Sprague-Dawley male rats were divided into 3 groups: group 1 was the control. Rats in groups 2 and 3 were exposed to cigarette smoke starting 21 days prior to surgery for 3 times a day. In group 3, additional 150 IU/kg rHuEPO was given via subcutaneously every 48 hours after microvascular anastomosis, femoral arterial samples, and blood samples were taken for assessment at 1st, 3rd, 5th, and 7th day. Intimae/media ratios were calculated for morphologic analyses.On morphologic analysis of femoral arteries there were statistically significant differences for all 3 groups at 1st, 3rd, 5th, and 7th days (P < 0, 05). The group that made differences was group 2, according to one-way analysis of variance within 3 groups in all days.Smoking decreases endothelial cells healing and causes more thromboses. rHuEPO can prevent these negative effects of smoking.

Reoxygenation attenuates the adhesion of neutrophils to microvascular endothelial cells

In humans, the pathophysiological inflammation response subsequent to hypoxia and reoxygenation often leads to systemic inflammation and multiorgan failure. We applied a newly developed static interaction model using human polymorphonuclear neutrophils and microvascular endothelial cells to clarify the role of hypoxia and hypoxia/reoxygenation in vitro. Human dermal microvascular endothelial cell cultures (n = 7) were exposed to hypoxia and different reoxygenation periods and the adherence rate of neutrophils to the endothelial cells as well as to the protein matrix on the culture slide surface were determined by quantitative microscopy. Hypoxia clearly triggered neutrophil adhesion to human dermal microvascular endothelial cells whereas additional reoxygenation significantly decreased neutrophil adhesion. These in vitro findings suggest that systemic inflammation caused by increased neutrophil adherence to the microvascular endothelium is already initiated by hypoxia rather than by subsequent reoxygenation.

Poloxamer 188 protects against ischemia-reperfusion injury in a murine hind-limb model

BACKGROUND

Ischemia-reperfusion injury can activate pathways generating reactive oxygen species, which can injure cells by creating holes in the cell membranes. Copolymer surfactants such as poloxamer 188 are capable of sealing defects in cell membranes. The authors postulated that a single-dose administration of poloxamer 188 would decrease skeletal myocyte injury and mortality following ischemia-reperfusion injury.

METHODS

Mice underwent normothermic hind-limb ischemia for 2 hours. Animals were treated with 150 microl of poloxamer 188 or dextran at three time points: (1) 10 minutes before ischemia; (2) 10 minutes before reperfusion; and (3) 2 or 4 hours after reperfusion. After 24 hours of reperfusion, tissues were analyzed for myocyte injury (histology) and metabolic dysfunction (muscle adenosine 5'-triphosphate). Additional groups of mice were followed for 7 days to assess mortality.

RESULTS

When poloxamer 188 treatment was administered 10 minutes before ischemia, injury was reduced by 84 percent, from 50 percent injury in the dextran group to 8 percent injury in the poloxamer 188 group (p < 0.001). When administered 10 minutes before reperfusion, poloxamer 188 animals demonstrated a 60 percent reduction in injury compared with dextran controls (12 percent versus 29 percent). Treatment at 2 hours, but not at 4 hours, postinjury prevented substantial myocyte injury. Preservation of muscle adenosine 5'-triphosphate paralleled the decrease in myocyte injury in poloxamer 188-treated animals. Poloxamer 188 treatment significantly reduced mortality following injury (10 minutes before, 75 percent versus 25 percent survival, p = 0.0077; 2 hours after, 50 percent versus 8 percent survival, p = 0.032).

CONCLUSION

Poloxamer 188 administered to animals decreased myocyte injury, preserved tissue adenosine 5'-triphosphate levels, and improved survival following hind-limb ischemia-reperfusion injury.