Effects of Lidocaine on Random Skin Flap Survival in Rats Bin Cao, MD,* Liren Wang, MD,† Dingsheng Lin, MD,* Leyi Cai, MD,* and Weiyang Gao, MD*
BACKGROUND Use of a random skin flap is common for repairing wounds and for reconstruction. Lidocaine is a traditional local anesthetic that blocks sodium channels and has positive effects on ischemia–reperfusion injury. OBJECTIVE
To investigate the effects of lidocaine on random skin flap survival in rats.
MATERIALS AND METHODS McFarlane flaps were established in 20 rats divided into 2 groups. Lidocaine was injected in the lidocaine group, and the same concentration of saline was injected in the control group. The survival area of the flaps was measured on Day 7. Levels of inflammation were evaluated by hematoxylin and eosin (H&E)–stained slices, and superoxide dismutase and malonyldialdehyde contents were examined. RESULTS The mean survival area of the flaps in the lidocaine group was significantly larger than that in the control group. Superoxide dismutase activity increased significantly in the lidocaine group compared with that in the control group. Malonyldialdehyde level in the lidocaine group was significantly lower than that in the control group. The H&E-stained slices showed that inflammation was clearly inhibited in the lidocaine group. CONCLUSION
Lidocaine improved the survival of random skin flaps.
The authors have indicated no significant interest with commercial supporters.
ocal random pattern skin flaps are frequently used in plastic surgery to reconstruct various defects. However, distal necrosis of the flaps remains a challenging problem. The length-to-width ratio cannot be >1.5 to 2:1, which limits clinical applications of random skin flaps. According to recent studies,1,2 ischemia–reperfusion injury, deficiency of blood supply, and hemodynamic injury are responsible for flap necrosis. Pharmacologic agents have been used to prevent or reverse skin flap ischemia, such as EMLA (a mixture of lidocaine and prilocaine)3 and vascular endothelial growth factor.4
L
Lidocaine is a traditional local anesthetic that blocks sodium channels. It enhances cutaneous blood flow,5 inhibits platelet aggregation,6 and suppresses
mitochondrial functions of neutrophils.7 Thus, lidocaine is effective for flap recovery after reperfusion injury.8 The potential effect of lidocaine on random skin flap survival was investigated in this study. The authors hypothesized that lidocaine would improve random skin flap survival because of its physiological characteristics. Materials and Methods Animals and Groups Twenty male 2-month-old Sprague–Dawley rats (weight, 200–250 g) were obtained by Wenzhou Medical University (SCXK [Zhe] 2005–0019) and treated in accordance with the Guide for the Care and Use of Laboratory Animals of Wenzhou Medical University. All rats were randomly divided into
*Department of Hand and Plastic Surgery, The Second Affiliated Hospital of Wenzhou Medical University, The Second Clinical Medical College of Wenzhou Medical University, Wenzhou, China; †The first Clinical Medical College of Wenzhou Medical University, Wenzhou, China Supported by Zhejiang Provincial Association of Integrative Medicine clinical pharmacy research (No. 2012LY015), and the Zhejiang Province Chinese medicine scientific research fund (No. 2014ZB074).
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© 2014 by the American Society for Dermatologic Surgery, Inc. Published by Lippincott Williams & Wilkins ISSN: 1076-0512 Dermatol Surg 2015;41:53–58 DOI: 10.1097/DSS.0000000000000241
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Copyright © American Society for Dermatologic Surgery. Unauthorized reproduction of this article is prohibited.
EFFECTS OF LIDOCAINE ON RANDOM SKIN FLAP
a lidocaine group (experimental group) and a saline group (control group). Each group contained 10 rats.
controlled room and were fed standard rat chow and water ad libitum. All surgeries were performed by 1 researcher, and no rats died during the procedure.
Reagents Lidocaine injectable (H32023260) was purchased from Xuzhou Ryen Pharma Co. (Xuzhou, China). Superoxide dismutase (SOD) and malondialdehyde (MDA) testing kits were purchased from Nanjing Jiancheng Biology Institution (Nanjing, China). Surgical Procedure The rats were anesthetized with 5% (wt/vol) chloral hydrate (8 mL/kg, intraperitoneal injection). A McFarlane flap model9 (9 · 3 cm) was designed and later modified on the same position of the dorsum of each rat. The caudally based flaps were raised, and both sacral arteries were sectioned systematically. The flap was completely separated from the deep fascia up to its base and then immediately sutured back to the donor bed using 4-0 silk and a wedged-on cutting needle.10 The flap area was divided into 3 distinct zones equally: the proximal zone was Area I, the intermediate zone was Area II, and the distal zone was Area III. Experimental Protocol Lidocaine was injected into the 3 zones of the rats in the lidocaine group (5 mg/kg, subcutaneous injection), and the same concentration of saline solution was injected into the 3 zones of rats in the control group. Injections were performed once per day for 7 days. Each rat had a neck collar (Figure 1) to prevent cannibalism or injury caused by normal socialization.11 An aseptic technique was rigorously applied during the procedure. All rats were housed individually in standard experimental cages in an environmentally
Testing Indicators Macroscopic Evaluation The survival area of each flap was observed, and the macroscopic changes during the 7 days, including appearance, color, texture, and hair condition were noted. Assessment of Surviving Areas All flaps were photographed, and the surviving areas were measured by superimposition of photographs on a graph paper. The results were expressed as a percentage of viable area calculated using the following formula: extent of viable area · 100/total area (viable and ischemic). Histopathological Evaluation The flap was divided into 3 parts of equal size: the proximal area (I), the intermediate area (II), and the distal area (III). Three samples (1 · 1 cm) of the central flap tissue were collected from each area and biopsied for histology. Each specimen was fixed in 10% paraformaldehyde for 24 hours. The specimens were embedded in paraffin, cut into 4 mm slices, and prepared for hematoxylin and eosin (H&E) staining. All sections were evaluated for neutrophil count under a light microscope (·100 magnification). Tissue Edema Measurements The flap was taken immediately after death on postoperative Day 7, weighed, and dehydrated in an autoclave at 50C. The samples were weighed daily until a constant weight was obtained for 2 days.
Figure 1. At the start of the experiment, the authors found that rats had a self-mutilation tendency, and they would bite the random flap on their back and cause the flap injury. (A) To stop this phenomenon, the authors tied a collar on their neck (B).
54
DERMATOLOGIC SURGERY
Copyright © American Society for Dermatologic Surgery. Unauthorized reproduction of this article is prohibited.
CAO ET AL
Figure 2. The digital photographs representing flaps from the 2 groups.
Water content of the tissues was used to evaluate the degree of edema.12 The percent water content of the tissue was determined by the following equation: Tissue% water content = ([wet weight 2 dry weight]/ wet weight) · 100. Analyses of Superoxide Dismutase Activity and Malondialdehyde Content Ten tissue specimens (0.5 · 0.5 cm) were obtained on postoperative Day 7 from Areas II and III of each group, weighed, homogenized, and diluted to 10% (vol/vol) in an ice bath. Superoxide dismutase activity was measured by the oxidase enzymatic method, and an MDA level was measured by a method based on a reaction with thiobarbituric acid at 90 to 100C.13
Mann–Whitney test. All data were analyzed with SPSS software 19.0 (SPSS Inc., Chicago, IL). A p value
BACKGROUND Use of a random skin flap is common for repairing wounds and for reconstruction. Lidocaine is a traditional local anesthetic that blocks sodium channels and has positive effects on ischemia–reperfusion injury. OBJECTIVE
To investigate the effects of lidocaine on random skin flap survival in rats.
MATERIALS AND METHODS McFarlane flaps were established in 20 rats divided into 2 groups. Lidocaine was injected in the lidocaine group, and the same concentration of saline was injected in the control group. The survival area of the flaps was measured on Day 7. Levels of inflammation were evaluated by hematoxylin and eosin (H&E)–stained slices, and superoxide dismutase and malonyldialdehyde contents were examined. RESULTS The mean survival area of the flaps in the lidocaine group was significantly larger than that in the control group. Superoxide dismutase activity increased significantly in the lidocaine group compared with that in the control group. Malonyldialdehyde level in the lidocaine group was significantly lower than that in the control group. The H&E-stained slices showed that inflammation was clearly inhibited in the lidocaine group. CONCLUSION
Lidocaine improved the survival of random skin flaps.
The authors have indicated no significant interest with commercial supporters.
ocal random pattern skin flaps are frequently used in plastic surgery to reconstruct various defects. However, distal necrosis of the flaps remains a challenging problem. The length-to-width ratio cannot be >1.5 to 2:1, which limits clinical applications of random skin flaps. According to recent studies,1,2 ischemia–reperfusion injury, deficiency of blood supply, and hemodynamic injury are responsible for flap necrosis. Pharmacologic agents have been used to prevent or reverse skin flap ischemia, such as EMLA (a mixture of lidocaine and prilocaine)3 and vascular endothelial growth factor.4
L
Lidocaine is a traditional local anesthetic that blocks sodium channels. It enhances cutaneous blood flow,5 inhibits platelet aggregation,6 and suppresses
mitochondrial functions of neutrophils.7 Thus, lidocaine is effective for flap recovery after reperfusion injury.8 The potential effect of lidocaine on random skin flap survival was investigated in this study. The authors hypothesized that lidocaine would improve random skin flap survival because of its physiological characteristics. Materials and Methods Animals and Groups Twenty male 2-month-old Sprague–Dawley rats (weight, 200–250 g) were obtained by Wenzhou Medical University (SCXK [Zhe] 2005–0019) and treated in accordance with the Guide for the Care and Use of Laboratory Animals of Wenzhou Medical University. All rats were randomly divided into
*Department of Hand and Plastic Surgery, The Second Affiliated Hospital of Wenzhou Medical University, The Second Clinical Medical College of Wenzhou Medical University, Wenzhou, China; †The first Clinical Medical College of Wenzhou Medical University, Wenzhou, China Supported by Zhejiang Provincial Association of Integrative Medicine clinical pharmacy research (No. 2012LY015), and the Zhejiang Province Chinese medicine scientific research fund (No. 2014ZB074).
·
© 2014 by the American Society for Dermatologic Surgery, Inc. Published by Lippincott Williams & Wilkins ISSN: 1076-0512 Dermatol Surg 2015;41:53–58 DOI: 10.1097/DSS.0000000000000241
·
·
· 53
Copyright © American Society for Dermatologic Surgery. Unauthorized reproduction of this article is prohibited.
EFFECTS OF LIDOCAINE ON RANDOM SKIN FLAP
a lidocaine group (experimental group) and a saline group (control group). Each group contained 10 rats.
controlled room and were fed standard rat chow and water ad libitum. All surgeries were performed by 1 researcher, and no rats died during the procedure.
Reagents Lidocaine injectable (H32023260) was purchased from Xuzhou Ryen Pharma Co. (Xuzhou, China). Superoxide dismutase (SOD) and malondialdehyde (MDA) testing kits were purchased from Nanjing Jiancheng Biology Institution (Nanjing, China). Surgical Procedure The rats were anesthetized with 5% (wt/vol) chloral hydrate (8 mL/kg, intraperitoneal injection). A McFarlane flap model9 (9 · 3 cm) was designed and later modified on the same position of the dorsum of each rat. The caudally based flaps were raised, and both sacral arteries were sectioned systematically. The flap was completely separated from the deep fascia up to its base and then immediately sutured back to the donor bed using 4-0 silk and a wedged-on cutting needle.10 The flap area was divided into 3 distinct zones equally: the proximal zone was Area I, the intermediate zone was Area II, and the distal zone was Area III. Experimental Protocol Lidocaine was injected into the 3 zones of the rats in the lidocaine group (5 mg/kg, subcutaneous injection), and the same concentration of saline solution was injected into the 3 zones of rats in the control group. Injections were performed once per day for 7 days. Each rat had a neck collar (Figure 1) to prevent cannibalism or injury caused by normal socialization.11 An aseptic technique was rigorously applied during the procedure. All rats were housed individually in standard experimental cages in an environmentally
Testing Indicators Macroscopic Evaluation The survival area of each flap was observed, and the macroscopic changes during the 7 days, including appearance, color, texture, and hair condition were noted. Assessment of Surviving Areas All flaps were photographed, and the surviving areas were measured by superimposition of photographs on a graph paper. The results were expressed as a percentage of viable area calculated using the following formula: extent of viable area · 100/total area (viable and ischemic). Histopathological Evaluation The flap was divided into 3 parts of equal size: the proximal area (I), the intermediate area (II), and the distal area (III). Three samples (1 · 1 cm) of the central flap tissue were collected from each area and biopsied for histology. Each specimen was fixed in 10% paraformaldehyde for 24 hours. The specimens were embedded in paraffin, cut into 4 mm slices, and prepared for hematoxylin and eosin (H&E) staining. All sections were evaluated for neutrophil count under a light microscope (·100 magnification). Tissue Edema Measurements The flap was taken immediately after death on postoperative Day 7, weighed, and dehydrated in an autoclave at 50C. The samples were weighed daily until a constant weight was obtained for 2 days.
Figure 1. At the start of the experiment, the authors found that rats had a self-mutilation tendency, and they would bite the random flap on their back and cause the flap injury. (A) To stop this phenomenon, the authors tied a collar on their neck (B).
54
DERMATOLOGIC SURGERY
Copyright © American Society for Dermatologic Surgery. Unauthorized reproduction of this article is prohibited.
CAO ET AL
Figure 2. The digital photographs representing flaps from the 2 groups.
Water content of the tissues was used to evaluate the degree of edema.12 The percent water content of the tissue was determined by the following equation: Tissue% water content = ([wet weight 2 dry weight]/ wet weight) · 100. Analyses of Superoxide Dismutase Activity and Malondialdehyde Content Ten tissue specimens (0.5 · 0.5 cm) were obtained on postoperative Day 7 from Areas II and III of each group, weighed, homogenized, and diluted to 10% (vol/vol) in an ice bath. Superoxide dismutase activity was measured by the oxidase enzymatic method, and an MDA level was measured by a method based on a reaction with thiobarbituric acid at 90 to 100C.13
Mann–Whitney test. All data were analyzed with SPSS software 19.0 (SPSS Inc., Chicago, IL). A p value
