The transepidermal absorption of prostaglandin E1 as a topical ointment: an experimental study of application over a rat skin flap

Effect of fractional ablative carbon dioxide laser with lidocaine spray on skin flap survival in rats

Background

Lidocaine spray is a local anesthetic that improves random-pattern skin flap survival. The fractional ablative carbon dioxide laser (FxCL) produces vertical microchannels that delivers topically applied drugs to the skin. In this study, we hypothesized that FxCL therapy would enhance the lidocaine effect to improve random-pattern skin flap survival in rats.

Methods

McFarlane random-pattern skin flaps were elevated in 48 rats, which were divided into four groups according to treatment: FxCL+lidocaine, FxCL, lidocaine, and nontreatment (control). On postoperative day 7, necrotic flap areas, the number of capillary vessels, and neutrophil count were evaluated. Anti-rat vascular endothelial growth factor (VEGF) and CD31 antibody activity were also evaluated by immunohistochemical staining.

Results

Flap survival rate was 53.41%± 5.43%, 58.16%± 4.80%, 57.08%± 5.91%, and 69.08%±3.20% in the control, lidocaine, FxCL, and FxCL+lidocaine groups, respectively. Mean neutrophil count in the intermediate zone excluding the necrotic tissue was 41.70± 8.40, 35.43± 6.41, 37.23±7.15, and 27.20± 4.24 cells/field in the control, lidocaine, FxCL, and FxCL+lidocaine groups, respectively. Anti-rat VEGF and CD31 antibody activity were the highest in the FxCL+lidocaine group.

Conclusion

FxCL with lidocaine had a positive effect on random-pattern skin flap survival in rats. Thus, FxCL with lidocaine spray should be considered as a new treatment option to improve flap viability.

Dipyrone increases the blood flow of arterial dorsal skin flaps

BACKGROUND

Findings have shown that dipyrone has a beneficial effect on skin flap survival. A pharmacologic explanation for this effect points to its vascular smooth muscle-relaxing effect. This study evaluated the effect of dipyrone on blood flow and thus survival of rat random dorsal skin flaps.

METHODS

For this study, 27 male Wistar albino rats were randomly assigned to control (treated with sterile saline) and treatment (treated with dipyrone 100 mg/kg) groups. A random dorsal skin flap measuring 4 x 10 cm was raised in each animal. The edges of the flap were sutured back into their original place. Dipyrone treatment continued at 100 mg/kg per day during the 7-day observation period. Blood flow was recorded by laser Doppler preoperatively (baseline), immediately after the flap was sutured back to its original position (acute), and on postoperative day 7. The degree of necrosis was evaluated by the grid method on day 7. Mean percentage necrosis and minimum laser Doppler readings were compared between the two groups.

RESULTS

A significant increase in blood flow was observed in the dipyrone group at the acute phase but not on postoperative day 7. The percentage of the necrotic area was lower in the treatment group. However, it did not reach the significance level (p = 0.09).

CONCLUSION

Dipyrone significantly increases [corrected] skin blood flow at the acute phase of flap elevation although the necrotic area does not reach the significance level.

Improved Flap Viability With Site-Specific Delivery of Sildenafil Citrate Using Fibrin Glue

Sildenafil is a cyclic guanosine-specific phosphodiesterase type 5 (PD-5) inhibitor that is widely used for erectile dysfunction. Potent and competitive inhibition of PD-5 enhances levels of cyclic guanosine monophosphate (cGMP). Fibrin glue-apart from tissue fixation-has been used for slow release of drugs. In this study, local delivery of Sildenafil citrate with fibrin glue was accomplished to improve random flap survival. Fifty Wistar rats were randomized into 5 groups, and a standardized dorsal random-pattern skin flap was elevated in each rat. In Group I (n = 10), the base of the flap was divided, making it a "graft" control to study the graft effect. In Group II (n = 10), a thin Silastic sheet was used to separate the flap from the underlying vascular bed, and no pharmacologic treatment was given. In Group III (n = 10), only 0.5 mL of fibrin glue was applied to the flap donor site. In Group IV (n = 10), 2.5 mg of sildenafil citrate mixed in 0.5 mL of fibrin glue was applied to donor site of the flap, whereas 10 mg of sildenafil citrate mixed in 0.5 mL of fibrin glue was applied in Group V (n = 10). Area of flap survival was evaluated on postoperative seventh day. Total necrosis of all of the flaps was observed in "graft" control group (Group I). Sildenafil and fibrin glue groups (Group IV and V) resulted in a statistically significant decrease in flap necrosis compared with Groups II and III (P < 0.0001). A statistically significant difference could not be documented between Group II and Group III (P > 0.0001). The decrease in skin necrosis was statistically significant in Group V compared with Group IV (P < 0.0001). Histologic examination revealed significantly increased vascular density in Groups IV and V compared with Groups II and III (P < 0.0001), whereas a significant difference could not be documented between Groups IV and V (P > 0.0001) and between Groups II and III (P > 0.0001). In view of these results, topical sildenafil application seems to improve flap survival in random-pattern skin flaps in dose-dependent manner.

The Effects of Topical Prostacyclin and Prostaglandin E1 on Flap Survival After Nicotine Application in Rats

The aim of this study is to examine and compare the effects of topical prostacyclin and prostaglandin E1 on flap survival after nicotine application in rats. In the designed experiment, group 1 was treated with 1 mL saline, and groups 2, 3, and 4 were treated with 2 mg/kg of nicotine subcutaneously for 4 weeks. At the end of 4 weeks, surgery was done, and topical applications of vaseline base on groups 1 and 2, prostacyclin (PgI2-iloprost) on group 3, and prostaglandin E1 (PgE1-misoprostol) on group 4 were performed. At the end of the seventh day following the operation, all survival areas in all groups were identified. For groups 1, 2, 3, and 4, survival areas were measured as 59.05% +/- 5.13%, 50.40% +/- 4.74%, 67.89% +/- 4.69%, and 62.45% +/- 7.80%, respectively. As a result, the authors concluded that survival areas can be increased with topical applications of these prostaglandins on the flaps (that are under nicotine effect), and there were no differences between these 2 medications in terms of flap survival.

Enhancement of dorsal random-pattern skin flap survival in rats with topical lidocaine and prilocaine (EMLA): Enhancement of flap survival by EMLA

BACKGROUND

Various topical pharmacologic agents have been investigated for their efficacy in preventing or reversing skin flap ischemia. Most of these studies have focused on agents that act on the vascular smooth muscles to cause vasodilatation and improve circulation in the flap. Most of local anesthetics relax vascular smooth muscle and produce peripheral vasodilatation. Topical lidocaine administration was shown that it was an effective and prompt resolution of mechanically induced vasospasm. The topical analgesia cream, EMLA is a mixture of the substances lidocaine and prilocaine. EMLA causes a biphasic vascular response comprising initial blanching and vasoconstriction (maximal after 1.5 h of application) and late erythema and vasodilatation at application times longer than 3 h.

MATERIALS AND METHODS

To investigate the effect of EMLA on random flap survival, 40 rats were divided in 2 groups of 20 animals. Caudally based random pattern skin flaps were elevated on dorsa of the rats in 10 x 3 cm dimensions. In group 1 which was the treatment group, topical EMLA was applied and covered with Opsite for 1 week whereas in group 2 which was the control group, carrier for EMLA was applied to the flaps. At the end of treatment period, the areas of flap necrosis were measured and percentages of flap survivals were calculated.

RESULTS

The mean percentages of flap survivals in group 1 and 2 were 81.2 +/- 1.2 percent and 58.7 +/- 2.3 percent, respectively.

CONCLUSION

Topically administered EMLA might lead to a significant improvement in flap survival. In addition, it is safe, cost-effective, easily applied, and clinically available.

Improved dorsal random-pattern skin flap survival in rats with a topically applied combination of nonivamide and nicoboxil

The effects of a topically applied combination of nonivamide and nicoboxil in improving skin perfusion and preventing distal flap necrosis were tested in a random-pattern dorsal skin flap model. Forty male Wistar rats were randomized into two groups (n = 20), and a standardized dorsal random-pattern skin flap was raised on each rat. Animals in the experimental group were treated with the topically applied drug combination four times per day for 6 days, whereas in the control group only a placebo ointment was applied each time. Skin flap viability was evaluated on day 7, and the extent of skin flap necrosis was compared between the two groups. The topically applied combination of nonivamide and nicoboxil resulted in a statistically significant decrease in skin flap necrosis, compared with the control group (mean percentage of skin flap necrosis in the nonivamide/nicoboxil-treated group, 22.6 +/- 6.0 percent; control group, 36.8 +/- 4.3 percent; p< 0.05). The topical combination of nonivamide and nicoboxil was effective in reducing ischemic necrosis in failing random-pattern skin flaps in this rat model. The results of this study suggest that such a topical drug application might have significant effects in the reduction of ischemic necrosis in the distal parts of skin flaps, and this treatment might also have applications as prophylactic therapy for risky skin flaps.