Systemic and flap inflammatory response associates with thrombosis in flap venous crisis

Roxadustat promotes hypoxia-inducible factor-1α/vascular endothelial growth factor signalling to enhance random skin flap survival in rats

Random skin flaps have limited clinical application as a broad surgical reconstruction treatment because of distal necrosis. The prolyl hydroxylase domain-containing protein inhibitor roxadustat (RXD) enhances angiogenesis and reduces oxidative stress and inflammation. This study explored the function of RXD in the survival of random skin flaps. Thirty-six male Sprague-Dawley rats were randomly divided into low-dose RXD group (L-RXD group, 10 mg/kg/2 day), high-dose RXD group (H-RXD group, 25 mg/kg/2 day), and control group (1 mL of solvent, 1:9 DMSO:corn oil). The proportion of surviving flaps was determined on day 7 after surgery. Angiogenesis was assessed by lead oxide/gelatin angiography, and microcirculation blood perfusion was evaluated by laser Doppler flow imaging. Specimens in zone II were obtained, and the contents of superoxide dismutase (SOD) and malondialdehyde (MDA) were measured as indicators of oxidative stress. Histopathological status was evaluated with haematoxylin and eosin staining. The levels of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and the inflammatory factors interleukin (IL)-1β, IL-6, and tumour necrosis factor-α (TNF-α) were detected by immunohistochemistry. RXD promoted flap survival and microcirculatory blood perfusion. Angiogenesis was detected distinctly in the experimental group. SOD activity increased and the MDA level decreased in the experimental group. Immunohistochemistry indicated that the expression levels of HIF-1α and VEGF were increased while the levels of IL-6, IL-1β, and TNF-α were decreased after RXD injection. RXD promoted random flap survival by reinforcing vascular hyperplasia and decreasing inflammation and ischaemia-reperfusion injury.

The Role of von Willebrand Factor in Microvascular Surgery in Severely Injured Patients

Microvascular anastomosis has become a standard surgical technique for reconstruction because of increasing possibilities, indications, and clinical success regarding the survival of the flaps. However, the main dreaded complications exist in thrombosis. Leaving surgical complications aside, systemic problems like disorder of the coagulation-fibrinolysis system are a significant cause of graft loss usually being unrecognized. Reports exist describing a hypercoagulable state with clotting activation and inhibition of fibrinolysis after trauma and delayed surgery considering the secondary homeostasis. In this clinical case, a patient had a large soft tissue defect at the temporal side of the head after severe trauma. After some days of primary stabilization, reconstruction using a free microvascular latissimus dorsi flap was performed. Multiple revisions of the arterial and venous branches had to be performed intraoperatively due to insufficient flap perfusion. After 24 hours, definitive flap loss occurred due to multiple thrombosis in the arterial and venous branches. Postoperative comprehensive coagulation analysis revealed a distinct activation of primary hemostasis with massively increased von Willebrand factor parameters and factor VIII activity as well as acetylsalicylic acid resistance contributing to thrombotic occlusion. In severely injured patients, comprehensive preoperative determination of the coagulation status (especially those of the primary hemostasis) is indispensable before performing free flap reconstruction surgeries to reduce the risk of microvascular flap loss.

Macrophage Migration Inhibitory Factor-An Innovative Indicator for Free Flap Ischemia after Microsurgical Reconstruction

(1) Background: Nowadays, the use of microsurgical free flaps is a standard operative procedure in reconstructive surgery. Still, thrombosis of the microanastomosis is one of the most fatal postoperative complications. Clinical evaluation, different technical devices and laboratory markers are used to monitor critical flap perfusion. Macrophage migration inhibitory factor (MIF), a structurally unique cytokine with chemokine-like characteristics, could play a role in predicting vascular problems and the failure of flap perfusion. (2) Methods: In this prospective observational study, 26 subjects that underwent microsurgical reconstruction were observed. Besides clinical data, the number of blood leukocytes, CRP and MIF were monitored. (3) Results: Blood levels of MIF, C-reactive protein (CRP) and leukocytes increased directly after surgery. Subjects that needed surgical revision due to thrombosis of the microanastomosis showed significantly higher blood levels of MIF than subjects without revision. (4) Conclusion: We conclude that MIF is a potential and innovative indicator for thrombosis of the microanastomosis after free flap surgery. Since it is easy to obtain diagnostically, MIF could be an additional tool to monitor flap perfusion besides clinical and technical assessments.

The secretome of stressed peripheral blood mononuclear cells increases tissue survival in a rodent epigastric flap model

Reconstructive surgery transfers viable tissue to cover defects and to restore aesthetic and functional properties. Failure rates after free flap surgery range from 3 to 7%. Co-morbidities such as diabetes mellitus or peripheral vascular disease increase the risk of flap failure up to 4.5-fold. Experimental therapeutic concepts commonly use a monocausal approach by applying single growth factors. The secretome of γ-irradiated, stressed peripheral blood mononuclear cells (PBMCsec) resembles the physiological environment necessary for tissue regeneration. Its application led to improved wound healing rates and a two-fold increase in blood vessel counts in previous animal models. We hypothesized that PBMCsec has beneficial effects on the survival of compromised flap tissue by reducing the necrosis rate and increasing angiogenesis. Surgery was performed on 39 male Sprague-Dawley rats (control, N = 13; fibrin sealant, N = 14; PBMCsec, N = 12). PBMCsec was produced according to good manufacturing practices (GMP) guidelines and 2 ml were administered intraoperatively at a concentration of 2.5 × 107 cells/ml using fibrin sealant as carrier substance. Flap perfusion and necrosis (as percentage of the total flap area) were analyzed using Laser Doppler Imaging and digital image planimetry on postoperative days 3 and 7. Immunohistochemical stainings for von Willebrand factor (vWF) and Vascular Endothelial Growth Factor-receptor-3 (Flt-4) were performed on postoperative day 7 to evaluate formation of blood vessels and lymphatic vessels. Seroma formation was quantified using a syringe and flap adhesion and tissue edema were evaluated clinically through a cranial incision by a blinded observer according to previously described criteria on postoperative day 7. We found a significantly reduced tissue necrosis rate (control: 27.8% ± 8.6; fibrin: 22.0% ± 6.2; 20.9% reduction, p = .053 vs. control; PBMCsec: 19.1% ± 7.2; 31.1% reduction, p = .012 vs. control; 12.9% reduction, 0.293 vs. fibrin) together with increased vWF+ vessel counts (control: 70.3 ± 16.3 vessels/4 fields at 200× magnification; fibrin: 67.8 ± 12.1; 3.6% reduction, p = .651, vs. control; PBMCsec: 85.9 ± 20.4; 22.2% increase, p = .045 vs. control; 26.7% increase, p = .010 vs. fibrin) on postoperative day 7 after treatment with PBMCsec. Seroma formation was decreased after treatment with fibrin sealant with or without the addition of PBMCsec. (control: 11.9 ± 9.7 ml; fibrin: 1.7 ± 5.3, 86.0% reduction, 0.004 vs. control; PBMCsec: 0.6 ± 2.0; 94.8% reduction, p = .001 vs. control; 62.8% reduction, p = .523 vs. fibrin). We describe the beneficial effects of a secretome derived from γ-irradiated PBMCs on tissue survival, angiogenesis, and clinical parameters after flap surgery in a rodent epigastric flap model.

Protective effects of dexmedetomidine on the survival of random flaps

BACKGROUND

Random flaps can be used to repair wounds and improve shape and functional reconstruction, but inflammation and necrosis limit their application. Modified McFarlane flap models were constructed on the backs of rats. We hypothesized that dexmedetomidine (DEX) could improve the survival rate of ischemic random flaps.

METHODS

Sixty rats were randomly divided into three groups: a low-dose DEX group (DEX-L group, 10 μg/kg/D), a high-dose DEX group (DEX-H group, 20 μg/kg/D) and a control group (0.9 % saline equivalent). On day 7 after flap construction, the survival percentage of the flap model was calculated. Hematoxylin and eosin staining (H&E) was used to evaluate the histopathological status of the flaps and microvessel density (MVD). Lead oxide/gelatin angiography was used to detect angiogenesis, and laser Doppler flow imaging (LDF) was used to detect blood perfusion. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in the middle areas of the flaps were measured to show the level of oxidative stress. The expressions of Toll-like receptor (TLR4), nuclear factor-kappa B (NF-κB), interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) were detected by immunohistochemistry.

RESULTS

DEX significantly increased the average survival percentage of the flaps and reduced ischemia and necrosis of the distal end of the flaps. SOD activity significantly increased, while MDA significantly decreased, indicating that DEX reduces oxidative damage. The expression of inflammatory immunoregulatory proteins (TLR4, NF-κB) was downregulated, and the levels of inflammatory factors (IL-1β, IL-6 and TNF-α) were lower. In addition, DEX upregulated VEGF expression, promoted angiogenesis, and increased blood perfusion.

CONCLUSION

In random flap transplantation, a high dose of DEX is beneficial to flap survival.

Tetramethylpyrazine improved the survival of multiterritory perforator flaps by inducing angiogenesis and suppressing apoptosis via the Akt/Nrf2 pathway

Background: Multiterritory perforator flaps were commonly designed to cover the large soft-tissue defects in reconstructive surgery. But the high risk of partial necrosis in the distal portion of the flaps hindered their clinical application. The purpose of this study was to evaluate the effects of tetramethylpyrazine (TMP) on the survival of the multiterritory perforator flaps and to explore the underlying mechanism.

Materials and methods: Seventy-two Sprague–Dawley rats underwent multiterritory perforator flap procedure and were divided into three groups with 24 each. Flap survival and water content were measured, and the area of angiogenesis and apoptosis in the ischemia skin flaps were assessed on the postoperative day 7. The expressions of angiogenesis-related protein VEGF and apoptosis-related protein Bax, Bcl-2 in each group were detected by Western blotting, which also had been used to assess the expressions levels of Akt, p-Akt, and Nrf2.

Results: Following TMP treatment, the survival area and number of microvessels presented in the skin flaps increased and tissue edema reduced on postoperative day 7. The expressions of angiogenesis-related protein VEGF increased in the TMP treatment group than in the control group. In addition, compared with the control group, TMP inhibited apoptosis, and increased the expression levels of p-Akt, Nrf2 in the areas of ischemia. These effects were reversed by an Akt protein inhibitor LY294002. Similarly, treatment with LY294002 inhibited TMP induced by interfering the Akt/Nrf2 signaling pathway.

Conclusion: These results illustrated that TMP could promote the survival of multiterritory perforator flaps by enhancing angiogenesis and attenuating apoptosis. These were involved in Akt/Nrf2 signaling pathway.

A Preliminary Study of the Effects of Venous Drainage Position on Arterial Blood Supply and Venous Return within the Conjoined Flap

Background:

Conjoined flap viability is associated with arterial blood supply and venous return. This study aimed to assess the effects of venous drainage position on arterial blood supply and venous return within the conjoined flap.

Methods:

Fifty-four rats were divided randomly into three groups (n = 18 per group). In experimental group 2, only the right intercostal posterior artery and the left iliolumbar vein were maintained; meanwhile, only the right intercostal posterior artery and the left intercostal posterior vein were preserved in experimental group 1. The control group had only the right intercostal posterior artery and vein preserved. The distances between angiosomes were measured. At 7 days after surgery, flap survival was evaluated, lead oxide–gelatin flap angiography was performed, and average microvessel density was assessed by hematoxylin and eosin staining, and lactate levels were assessed.

Results:

The distance between angiosomes I and II was the shortest, whereas angiosomes I and III were most distant (p < 0.05). At 7 days after surgery, survival rates in experimental group 2 and experimental group 1 were both 100 percent, whereas 86.5 ± 1.6 percent of controls survived. Furthermore, angiogenesis was more obvious in experimental group 2 than in experimental group 1 and controls. Moreover, lactate levels were lower in experimental group 2 (7.47 ± 0.17 mM) and experimental group 1 (8.03 ± 0.31 mM) compared with control values (9.98 ± 0.37 mM; p < 0.05).

Conclusion:

Changes in position of venous drainage might cause continuous arterial high-pressure perfusion and venous superdrainage, which improves flap survival.

Prediction of Flap Compromise by Preoperative Coagulation Parameters in Head and Neck Cancer Patients

PURPOSE

Studies on coagulation parameters (including activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen [FIB], platelet count, and D-dimer) in flap compromise are limited. The aim of the present study was to compare coagulation parameter variables in patients with and without flap compromise.

MATERIALS AND METHODS

In this retrospective cohort study, patients were recruited from the Department of Oral and Maxillofacial Surgery at the Second Xiangya Hospital (Changsha, Hunan, China) from July 2016 through July 2017. The primary predictor variable was a set of coagulation parameters. The primary outcome variable was flap compromise. The other variables were age, gender, tumor stage, smoking, and prior radiotherapy. Descriptive, bivariate, receiver operating characteristic (ROC) curves and regression statistics were computed. Statistical significance was set at less than .05 with 95% reliability.

RESULTS

A total of 503 patients with 42 compromised flaps were identified in this study. Venous thrombosis, arterial thrombosis, or no confirmed reason for compromise was observed in 28, 5, or 9 compromised flaps, respectively. Only FIB was associated with flap compromise or venous thrombosis at adjusted analyses, although the predictive values were low at ROC analysis. For patients with D-dimer lower than 0.4 μg/mL, the likelihood of venous thrombosis was greater than that for patients with D-dimer of at least 0.4 μg/mL (P = .0414). For patients with FIB lower than 3.5 g/L, the likelihood of venous thrombosis was greater than that for patients with FIB of at least 3.5 g/L (P = .0336).

CONCLUSION

Decreased FIB was associated with a higher rate of flap compromise. In patients with D-dimer lower than 0.4 μg/mL or FIB lower than 3.5 g/L, the risk of venous thrombosis was higher.