Preoperative subcutaneous sildenafil injection increases random flap survival in rats

Use of Phosphodiesterase Inhibitors in the Postoperative Period of Skin Flaps: A Systematic Review

Ischemia-reperfusion injury can occur in several clinical conditions, and it has been widely studied in the context of skin flaps. Vascular distress results in an imbalance between the supply and demand of oxygen to living tissues, and the result of this process is tissue necrosis. Several drugs have been studied to reduce vascular distress of skin flaps and tissue loss.

Methods

The present study performed a systematic review of literature in the main databases (PubMed, Web of Science, LILACS, SciELO, and Cochrane), including articles published in the last 10 years.

Results

It was observed that phosphodiesterase inhibitors, mainly types III and V, have shown promising results in terms of vascularization of the postoperative skin flap, especially when started on the first postoperative day and maintained for 7 days.

Conclusion

New studies with different posology, duration of use, and new drugs are needed to better elucidate the use of this substance to optimize the circulation of skin flaps.

Standardization of the Rat Dorsal Random Pattern (McFarlane) Flap Model and Evaluation of the Pharmacological Agents Aiming to Salvage Partial Flap Necrosis: A Systematic Review and a Meta-analysis

INTRODUCTION

Partial flap necrosis is a common complication after surgery. McFarlane flap model has been used for assessment of various agents' effects on random flap survival. The aim of this study was to review the methodology of studies using this flap model and reveal the most successful agents.

MATERIALS AND METHODS

PubMed, Scopus, and Web of Science databases were screened for words "McFarlane flap," "flap survival," and ("flap" and "rat") by using time limits between 1965 and 2019. A total of 71 original articles were reviewed. Dimensions and base (cranial/caudal) of the flap, treatment protocol, follow-up period, and survival rates were extracted. Modified survival rates were calculated. Coefficients of variation of cranial/caudally based control group flaps and most commonly used flap models were calculated to assess interstudy variability.

RESULTS

A total of 165 different treatment regimens were studied. One-hundred twelve regimens (67.9%) were found to increase flap survival. Most common flap dimensions were 9 cm × 3 cm, followed by 10 cm × 3 cm, 8 cm × 2 cm and 6 cm × 2 cm. Studies using caudally based flaps showed less interstudy variability, but survival rates were similar. Pentoxifylline, sildenafil, chlorpromazine, phenoxybenzamine, and phentolamine were reported to be successful in multiple studies.

CONCLUSIONS

There are numerous agents found to be effective for treatment of partial flap necrosis, but further clinical research is needed. To overcome standardization problems, use of commonly used flap dimensions with a caudal base and interpretation of results after 7 days of follow-up seems appropriate.

The effect of different modes of microneedling technique on random flap survival in rats

OBJECTIVE

The investigation and practice of physical therapy in flap surgery are still scare. The purpose of this study is to evaluate the impact of different microneedling interventions on survival of random pattern flaps in rats, attempting to determine the optimal microneedling protocols for improvement of flap survival.

METHODS

Eighty male Sprague-Dawley rats were randomly divided into four groups, with 20 in each group (group A, B, C, and D). A 3 cm × 9 cm rectangular random flap as the McFarlane flap was adopted in each group. In groups A and B, microneedling treatment was performed before and after surgery, respectively. While animals in group C were received both pre- and postoperative microneedling treatment. Group D was used as a control group, which was only exposed to surgery. Flap survival, flap blood flow, number of capillary formations, the expressions of CD31, CD34, HIF-1α, and vascular endothelial growth factor (VEGF) were detected in each group and compared.

RESULTS

On the 7th day postoperatively, significant improvements with microneedling treatment were found in flap survival rate (p = 0.007), blood flow (p = 0.024), the expression levels of CD34 (p = 0.005), and the VEGF (p < 0.01). Furthermore, the VEGF expression level was significantly higher in group B when compared with the other three groups (all p < 0.01). However, there was no significant difference in the number of new blood vessels and other immunohistochemical indicators among the four groups (all p > 0.05).

CONCLUSION

Microneedling treatment especially postoperative intervention can significantly improve the survival of random flaps in rats.

Effects of sildenafil and tadalafil on skin flap viability

Vascular complication is one of the causes of skin flap healing failure. Sildenafil and tadalafil, a type-5 phosphodiesterase inhibitor, can improve flap viability, however, the action mechanisms involved in this process are still unclear. To assess the effects of orally administered sildenafil and tadalafil on the healing kinetics and skin flap viability, sixty-two Wistar rats were divided into three groups: control (n = 22), sildenafil (n = 20), and tadalafil (n = 20). The solutions were administered orally (dose: 10 mg/kg) immediately after the surgical procedure and then every 24 h. At postoperative days 7 and 14, the skin flap samples were collected, submitted to histological processing and evaluated under optical microscopy. In experimental groups (sildenafil and tadalafil), we found an increased vascularization (p < 0.05) on the 7th and 14th day associated with the ulcer size decrease on the 14th day, although it was not significant. There was a higher influx of neutrophils and a decrease of mononuclear population on the 7th day (p < 0.05). On the 14th day, these differences were observed only in the tadalafil group (p < 0.05). This study suggested positive results with the use of sildenafil and tadalafil as adjuvant drugs in skin flap viability.

Impact of sildenafil-containing ointment on wound healing in healthy and experimental diabetic rats

AIM

The study evaluated the effect of different concentrations of sildenafil-containing ointment on wound healing in healthy and streptozotocin (STZ)-induced diabetic rats.

METHODS

A total of 108 Sprague Dawley male rats aged 5 months were randomly divided into two groups: healthy and diabetes-inducing rats. Following induction of diabetes by intraperitoneal STZ injection (55 mg/kg), diabetic and healthy rats were subdivided into six groups (9 rats each). Linear incisions of the dorsal backs of rats were made. Then, rats were treated twice daily with either 2%, 2% + Fucidin, 5% sildenafil-containing ointments, oral sildenafil (13.0 mg/kg), moist exposed burn ointment or vehicle. During treatment, the percent reduction of the wound area and tensile strength were measured on days 3, 7 and 10. Furthermore, histopathology was performed on the wounded skin on similar days for the assessment of collagen synthesis and proliferation of new capillary vessels.

RESULTS

In healthy and STZ-induced diabetic rats, the percent reduction in wound area on day 3 was significantly higher in sildenafil-containing ointment-treated groups than all other groups, whereas on day 7 only the 5% sildenafil-containing ointment-treated group showed better response in healthy rats. Although the sildenafil-containing ointment significantly showed better tensile strength than all other groups, the 5% sildenafil-treated group significantly enhanced the tensile better than the 2% and 2% + Fucidin dose. Furthermore, the histological evaluation revealed that sildenafil-containing ointment promoted collagen synthesis and proliferation of new capillary vessels.

CONCLUSION

Our results suggest that sildenafil-containing ointment can provide an advantage in wound healing by promoting wound contractions and resistance to wound breakage in healthy and diabetic conditions. Therefore, 5% sildenafil-containing ointment can be used as a support factor for wound healing in healthy and diabetic conditions; however, clinical trials are required to confirm the benefits of sildenafil in wound healing.

The Effects of Sildenafil and/or Nitroglycerin on Random-pattern Skin Flaps After Nicotine Application in Rats

Smoking aggravates skin necrosis as a complication of random-pattern flap ischaemia. Sildenafil and nitroglycerin (NTG) are vasodilator agents that may affect skin flap survival. Fifty rats were subjected to a dorsal random-pattern flap operation and randomly divided into 5 groups. The control group received no treatment. The ischaemic group were administered local nicotine injections. The sildenafil group were administered oral sildenafil treatment in addition to the same intervention as the ischaemic group. The NTG group received topical NTG ointment application instead of sildenafil. The combined group were given both sildenafil and NTG treatments. After 7 days, all rats were sacrificed for flap assessment. Flap survival percentages at the 3^rd and 7^th days were significantly higher in the combined group than in the other study groups. Histologically, the ischaemic group exhibited dermal disorganization and inflammatory cell infiltration, which were improved in the 3 treated groups; however, the combined group presented the most relevant effect. The epidermal thickness showed a decrease in the ischaemic group (23.1 μm) that was significantly increased in the sildenafil (28.4 μm), NTG (28.8 μm) and combined (35.8 μm) groups. Immunohistochemically, the combined group exhibited a significant decrease in the apoptotic index and an increase in the proliferative index (2.3 and 56.9%, respectively) compared to those in the ischaemic (63.2 and 3%), sildenafil (41.7 and 28.1%) and NTG (39.3 and 30.4%) groups. Transmission electron microscopy (TEM) showed that the combined group displayed improvement in most of the ischaemic changes. Our analyses suggest that the combined use of sildenafil and NTG is more efficacious than using only one of these treatments for skin flap survival.

Comparison of incisional delay patterns on a rat random flap model

One of the simplest form of surgical delay can be performed by placing an incision around the flap without undermining, prior to flap elevation. In this study, we have compared the efficiency of different patterns of skin incision to improve flap survival. Twenty-eight animals were used in four groups. Incisional delay was performed prior to flap elevation in the three experiment groups. Complete incision of the three flap edges was performed in the all experiment groups with the exception of an intact skin section on the middle 1/3rd of the bilateral edges in group 1 (bilateral skin edge preserved delay: BSEPD), of a unilateral edge in group 2 (unilateral skin edge preserved delay: USEPD) and of the superior edge in group 3 (superior skin edge preserved delay: SSEPD) without any undermining. Two weeks following the delay procedure, dorsal skin flaps were raised and reinserted back to their place. The results were evaluated with the measurement of necrotic flap area, microangiographic imaging and histological evaluation. The mean percentage of necrotic flap area to whole flap area was 16.94%, 7.54%, 23.34% and 50.6% in the BSEPD, USEPD, SSEPD and control groups, respectively. In selected microangiographic images, vessels were more prominent in the delay groups. The results of the study indicate that three sided incision with an intact skin on the superior edge is not effective in providing a sufficient delay and flap survival improvement when compared to incisions with intact skin on the unilateral and bilateral edges.

Subdermal nitrous oxide delivery increases skin microcirculation and random flap survival in rats

Random skin flaps are essential tools in reconstructive surgery. In this study, we investigated the effect of subdermal nitrous oxide (N₂O) application on random flap survival. In this experimental study, we used 21 female rats in three groups. In the N₂O and air groups, gases were administrated under the proposed dorsal flap areas daily for seven days. Following the treatment period, flaps were raised and inserted back into their place from the dorsal skin. In the control group, the flaps were elevated and inserted back to their place without any pretreatment. Calculation of necrotic flap areas, histological examination and microangiography was performed to evaluate the results 7 days after the flap surgery. The average of necrotic flap area in the N₂O, air and control group was 13.45%, 37.67% and 46.43%, respectively. (N₂O vs air p = .044; N₂O vs control p = .003). The average number of capillary formations identified in the histological analysis was 7.0 ± 1.58, 3.75 ± 2.36 and 4.4 ± 0.54 in the N₂O, air and control group, respectively. (N₂O vs air p = .017; N₂O vs control p = .037). The average number of capillary structures identified in the angiography images were 6.3 ± 1.52, 1.6 ± 1.15 and 1.3 ± 0.57 in the N₂O, air and control group, respectively. (N₂O vs air p = .04; N₂O vs control p = .02). We conclude that subdermal N₂O application increases random flap survival through an increase in the skin microcirculation and could be promising for future clinical applications.