Skin Flap Surgery Research Articles

Vasodilator effect and mechanism of action of vascular endothelial growth factor in skin vasculature.

Various laboratories have reported that local subcutaneous or subdermal injection of VEGF(165) at the time of surgery effectively attenuated ischemic necrosis in rat skin flaps, but the mechanism was not studied and enhanced angiogenesis was implicated. In the present study, we used the clinically relevant isolated perfused 6 x 16-cm pig buttock skin flap model to 1) test our hypothesis that VEGF(165) is a potent vasodilator and acute VEGF(165) treatment increases skin perfusion; and 2) investigate the mechanism of VEGF(165)-induced skin vasorelaxation. We observed that VEGF(165) (5 x 10(-16)-5 x 10(-11) M) elicited a concentration-dependent decrease in perfusion pressure (i.e., vasorelaxation) in skin flaps preconstricted with a submaximal concentration of norepinephrine (NE), endothelin-1, or U-46619. The VEGF(165)-induced skin vasorelaxation was confirmed using a dermofluorometry technique for assessment of skin perfusion. The vasorelaxation potency of VEGF(165) in NE-preconstricted skin flaps (pD(2) = 13.57 +/- 0.31) was higher (P < 0.05) than that of acetylcholine (pD(2) = 7.08 +/- 0.24). Human placental factor, a specific VEGF receptor-1 agonist, did not elicit any vasorelaxation effect. However, a specific antibody to VEGF receptor-2 (1 microg/ml) or a specific VEGF receptor-2 inhibitor (5 x 10(-6) M SU-1498) blocked the vasorelaxation effect of VEGF(165) in NE-preconstricted skin flaps. These observations indicate that the potent vasorelaxation effect of VEGF(165) in the skin vasculature is initiated by the activation of VEGF receptor-2. Furthermore, using pharmacological probes, we observed that the postreceptor signaling pathways of VEGF(165)-induced skin vasorelaxation involved activation of phospholipase C and protein kinase C, an increase in inositol 1,4,5-trisphosphate activity, release of the intra-cellular Ca(2+) store, and synthesis/release of endothelial nitric oxide, which predominantly triggered the effector mechanism of VEGF(165)-induced vasorelaxation. This information provides, for the first time, an important insight into the mechanism of VEGF(165) protein or gene therapy in the prevention/treatment of ischemia in skin flap surgery and skin ischemic diseases.

Effect of nicotine on vasoconstrictor and vasodilator responses in human skin vasculature.

Our objective was to test the hypothesis that acute exposure of human skin vasculature to nicotine may have deleterious effects on endothelial function. Vasoconstriction and vasorelaxation in isolated perfused human skin flaps (approximately 8 x 18 cm) derived from dermolipectomy specimens were assessed by studying changes in skin perfusion pressure measured by a pressure transducer, and skin perfusion was assessed by a dermofluorometry technique (n = 4 or 5). It was observed that nicotine (10(-7) M) amplified (P < 0.05) the norepinephrine (NE)-induced concentration-dependent (10(-7)-10(-5) M) increase in skin vasoconstriction compared with the control. This amplification effect of nicotine in NE-induced skin vasoconstriction was not blocked by the nicotine-receptor antagonist hexamethonium (10(-6) M) or the cyclooxygenase inhibitor indomethacin (10(-5) M). It was also observed that ACh and nitroglycerin (NTG) elicited a concentration-dependent (10(-8)-10(-5) M) vasorelaxation in skin flaps preconstricted with 8 x 10(-7) M of NE. The vasorelaxation induced by ACh was attenuated (P < 0.05) in the presence of nicotine (10(-7) M) compared with the control. However, skin vasorelaxation induced by NTG was not affected by nicotine (10(-7) M). ACh and NTG are known to induce endothelium-dependent and -independent vasorelaxation, respectively. The present findings were interpreted to indicate that acute exposure of human skin vasculature to nicotine was associated with 1) amplification of NE-induced skin vasoconstriction and 2) impairment of endothelium-dependent skin vasorelaxation. Cyclooxygenase products and nicotine receptors blocked by hexamethonium were not involved in the amplification of NE-induced skin vasoconstriction by nicotine. These findings may provide further insight into the pathogenesis of skin vasospasm in skin flap surgery and skin ischemic disease associated with cigarette smoking or use of smokeless tobacco.

Mannitol in reperfusion skin island flaps injury

In the skin, the concept of reperfusion injury is well established. The application of this knowledge to deal with skin flap surgery problems, has a great prophylactic potential. This experimental study was performed to evaluate the action of mannitol as a scavenger of oxygen-free radicals, after an ischemia-reperfusion injury on skin island flaps. Thirty six male Wistar rats were divided into three test groups (n = 12): a non-ischemic group (group I), and two others (groups II and III) which were subjected to nine hours of ischemia following by 30 minutes of reperfusion. After seven days, all animals of group II, treated with saline, showed full skin flap necrosis. The assessment of group III, that received a 20% solution of mannitol prior to the onset of reperfusion, revealed 75% (9/12) of flap viability. These results suggest that pre-treatment with mannitol is able to enhance flaps survival with significantly less tissue necrosis (p &lt;0.02).

Smoking increases facial skin flap complications.

This study was undertaken to determine whether smokers have a higher risk of complications after reconstruction of facial skin defects. Ninety-one patients with facial skin defects reconstructed with local flaps were reviewed retrospectively. Thirty-eight (42%) were active smokers, 12 (13%) had not smoked for at least 1 year prior to surgery, and the rest were nonsmokers. Complications occurred in 23 patients (25%; 37% in smokers, 17% in ex-smokers, and 17% in nonsmokers; p < .03). All full-thickness skin losses and all cellulitis occurred in active smokers. We conclude that active smokers are at a higher risk for complications in facial skin flap surgery. That ex-smokers had a complication rate similar to that of nonsmokers suggests that part of smoking's adverse effect on skin flaps may be an acute phenomenon, and that smoking cessation for shorter (<1 year) periods of time before surgery may have a beneficial effect.

Nitric oxide synthase activity and endothelial ultrastructure in ischaemic skin-flaps

The aim of the present study was to detect and quantify nitric oxide synthase (NOS) activity and to investigate morphological changes in the endothelium in two different ischaemic dorsal flap models in the rat, one based cranially and one based caudally. Intact skin from the dorsum was used as control. In both groups flaps were removed at l, 4, 12, 24 and 72 h after surgery respectively. NOS-activity was measured by the conversion of L-arginine to L-citrulline and endothelial morphology was investigated using transmission electron microscopy. Intact skin showed Ca 2+-dependent but no Ca 2+-independent NOS-activity. A time-dependent decrease in Ca 2+-dependent NOS-activity was seen in the proximal and distal part of the flaps in both flap models and was most pronounced in the distal part. Ca 2+-independent NOS-activity increased in the proximal and distal part of flaps based cranially and in the proximal part of flaps based caudally. Morphological analysis of the endothelium showed signs of endothelial damage including blebbed membranes, swelling and endothelial loss. These findings show that ischaemia caused by skin-flap surgery leads to endothelial damage and a decrease in Ca 2+-dependent nitric oxide synthase activity. Furthermore, in the skin-flaps an induction of Ca 2+-independent nitric oxide synthase (iNOS) activity was noted both in surviving flap tissue and in flap tissue destined to necrose.

Evidence for nicotine-induced skin flap ischemic necrosis in the pig.

There is clinical and experimental evidence to indicate that cigarette smoking may increase the risk of skin ischemic necrosis in flap surgery but the pathogenic mechanism remains unclear. The objectives of this project were to investigate the potential deleterious effects and mechanism of action of nicotine, a major by-product of cigarette smoking, in skin flap surgery in the pig. It was observed that 4-5 weeks of intramuscular nicotine injections (4 mg/kg; twice daily) significantly (p < 0.05) decreased the skin flap capillary blood flow and the length and area of skin flap viability in the pig. This nicotine treatment also induced a 1.6-fold increase in skin flap tissue content of norepinephrine compared with the saline-treated control. The estimated mean wet skin tissue content of norepinephrine (5 x 10(-7) M) was much higher than the circulating level of norepinephrine (1.8 x 10(-9) M) in nicotine-treated pigs. This level of norepinephrine (5 x 10(-7) M) was seen to induce a significant vasoconstrictor effect (75% increase over basal perfusion pressure) in isolated perfused pig skin flaps. It was also observed that the vasoconstrictor effect of norepinephrine was significantly (p < 0.05) enhanced in the presence of 10(-4) M N omega-monomethyl-L-arginine or NG-nitro-L-arginine, an endothelium-derived relaxing factor--nitric oxide (EDRF/NO) synthesis inhibitor. This vasoconstrictor effect was further enhanced in the presence of NG-nitro-L-arginine and 10(-5) M indomethacin, a cyclooxygenase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacologic Intervention of Skin Vasospasm and Ischemic Necrosis in Pigs

Ischemic necrosis resulting from vasospasm is a common complication in skin flap surgery, and serotonin released by traumatized platelets is likely to play an important role in the pathogenesis of skin vasospasm in flap surgery. We studied the pathogenic role of serotonin and its pharmacologic intervention thereof in skin flap ischemic necrosis in pigs. We observed that serotonin caused a concentration-dependent (10(-8)-10(-5) M) increase in perfusion pressure in isolated perfused pig skin flaps. This vasoconstrictive effect of serotonin was blocked by S1C/2-serotonergic receptor antagonists LY53857 (10(-5) M) and ketanserin (10(-5) M), but not by an alpha 1-adrenoceptor antagonist (prazosin 10(-5) M), or a thromboxane A2 (TxA2)/endoperoxide receptor antagonist (SQ30741 10(-5) M). The vasoconstrictive effect of serotonin was more pronounced (p < 0.05) in the presence of an endothelium-derived nitric oxide (NO) synthesis inhibitor [N omega-monomethyl-L-arginine (L-NA) or NG-nitro-L-arginine (L-NMMA) 10(-5) M] but not a cyclooxygenase inhibitor (indomethacin 10(-5) M). In in vivo studies, serotonin infusion (5 micrograms/kg/min intravenously, i.v.) significantly (p < 0.05) decreased pig random pattern skin flap capillary blood flow. This in vivo vascular effect was also completely blocked in pigs pretreated with LY53857 (0.4 mg/kg i.v.). In a separate experiment without serotonin infusion, i.v. prazosin (2-8 micrograms/kg), dazmegrel (2-6 mg/kg), or SQ30741 (2-4 mg/kg) had no significant effect on skin flap capillary blood flow as compared with control. On the other hand, i.v. sergolexole or LY53857 significantly (p < 0.05) increased skin flap capillary blood flow in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Augmentation of acute random pattern skin flap viability in the pig

Three experiments were conducted to study the effect of ketanserin and LY53857, S 2-serotonergic receptor antagonists, on skin blood flow and viability in acute random pattern skin flaps (4 × 10 cm) in the pig. In experiment 1, the dose-response effect of intravenous ketanserin (0, 0.15, 0.25, 0.35, and 0.50 mg/kg) on skin flap capillary blood flow was studied 6 hr after skin flap surgery, using the radioactive microsphere (15 μm) technique and under pentobarbital anesthesia. Significant ( P < 0.05) increase in skin flap blood flow was seen at the dosages of 0.25 and 0.35 mg/kg compared with the saline-treated control. In experiment 2, the effect of five-day intramuscular ketanserin and LY53857 treatment (0.30 mg/kg/day; in divided doses) on skin flap viability was studied. The drug treatments were started two days preoperatively. It was observed that the length of skin flap viability in ketanserin (6.6 ± 0.2 cm; n = 40 flaps) and LY53857 (6.8 ± 0.3 cm; n = 40 flaps) treated flaps were significantly ( P < 0.05) higher than the saline-treated control (5.5 ± 0.1 cm; n = 48 flaps). Ketanserin treatment started 30 min after flap surgery also significantly ( P < 0.05) increased the length of skin flap viability (6.1 ± 0.1 cm) compared with the control. There was no significant difference in skin viability between ketanserin and LY53857 treated skin flaps. The preceding study on the effect of ketanserin treatment on random pattern skin flap viability was repeated in experiment 3. Again, it was observed that intramuscular ketanserin treatment significantly ( P < 0.05) increased the skin flap viability. It was concluded that ketanserin and LY53857 treatment resulted in significant augmentation of porcine acute random pattern skin flap viability. This is the first experimental evidence to indicate that S 2-serotonergic receptors participate in the pathogenesis of skin flap ischemia.

In vivo phosphorus NMR spectroscopy of skin using a crossover surface coil

A modified crossover surface coil with minimal B1 field penetration was used for collection of skin phosphorus NMR spectra. Projection imaging experiments show that the coil-sensitive volume is uniform at the phosphorus frequency, but strikingly nonuniform at the proton frequency. Experiments with an in vitro phosphorus phantom, designed to simulate skin and underlying tissue, demonstrated that 45.1% (+/- 1.2%) of total signal was derived from Sprague-Dawley rat skin and 19.3% (+/- 1.4%) of total signal was derived from Fischer-344 rat skin. 31P MR spectra of rat skin in vivo permitted resolution of four phosphorus compounds: nucleoside triphosphates, phosphocreatine (PCr), inorganic phosphate (Pi), and phosphomonoester. Spectra collected after skin flap surgery in Fischer-344 rats showed a 50.1% (+/- 7.6%) reduction in the ratio of PCr/Pi within 30 min of surgery, compared to presurgical PCr/Pi levels (P less than 0.01). Skin phosphorus spectra are potentially useful for assessment of skin flap and skin graft viability.

Efficacy of intravenous infusion of prostacyclin (PGI 2) or prostaglandin E 1 (PGE 1) in augmentation of skin flap blood flow and viability in the pig

The dose-response effects of 6-h intravenous infusion of PGI 2 (0, 5, 10, 25 or 75 ng/kg/min) or PGE 1 (0, 25, 50, 100 or 300 ng/kg/min) on skin hemodynamics and viability were studied in 4 × 10 cm random pattern skin flaps (n=24) raised on both flanks of the pig. Infusion of PGI 2 or PGE 1 was started immediately after intravenous injection of a loading dose 30 min before skin flap surgery. PGI 2 infusion significantly (P<0.05) increased the total skin flap capillary blood flow at the dose of 10 ng/kg/min, compared with the control. However, the distance of blood flow along the skin flap from the pedicle to the distal end, i.e. perfusion distance, was not increased. Consequently, the length and area of skin flap viability was also not significantly increased. The effect of PGI 2 infusion on skin blood flow was biphasic. Specifically, higher doses (≥ 25 ng/kg/min) of intravenous PGI 2 infusion produced no beneficial effect on the skin flap capillary blood flow. PGI 2 infusion at the dose of 10 or 75 ng/kg/min did not significantly increased plasma renin activities or plasma levels of norepinephrine compared with the control, therefore the biphasic effect of PGI 2 on skin flap blood flow was not related to circulating levels of norepinephrine or angiotensen. Intravenous infusion of PGE 1 did not produce any therapeutic effect on the skin capillary blood flow in the random pattern skin flaps at all doses tested. At the dose of 300 ng/kg/min, the mean arterial blood pressure was 17% lower (P<0.05) than the control, but the skin capillary flow still remained similar to the control. It was concluded that intravenous infusion of PGI 2 or PGE 1 was not effective in augmentation of distal perfusion or length of skin viability in the porcine random pattern skin flaps. Drug treatment modalities for prevention or treatment of skin flap ischemia is discussed.

Pathogenesis of Ischemic Necrosis in Random-Pattern Skin Flaps Induced by Long-Term Low-Dose Nicotine Treatment in the Rat

The objectives of the present experiments were to study the effects of long-term low-dose nicotine treatment on skin hemodynamics, viability, and microvascular morphology in 4 x 10 cm dorsally based acute random-pattern skin flaps in the rat. In addition, the reversibility of the nicotine-induced detrimental effects on skin-flap viability following cessation of nicotine treatment also was investigated. Low-dose nicotine (0.6 mg/kg) administered twice daily and subcutaneously for 24 weeks significantly (p less than 0.05) decreased skin-flap capillary blood flow, distal perfusion, and length and area of skin viability compared with the saline-treated control (n = 15). However, these same parameters in rats (n = 15) whose nicotine treatment had been withheld for 2 weeks prior to skin-flap surgery were not significantly different from the control, thus indicating that the detrimental effects of this long-term, low-dose nicotine treatment were reversible. The mean plasma level of nicotine in the nicotine-treated rats was 8.1 +/- 0.4 micrograms/dl and was within the range of plasma nicotine levels reported for human heavy cigarette smokers. Light and electron microscopic studies did not show evidence of histologic damage to the cutaneous microvasculature in acute random-pattern skin flaps and samples of normal (nonoperated) skin in nicotine-treated rats. It is concluded that long-term plasma levels of nicotine similar to those of heavy cigarette smokers are detrimental to the capillary blood flow and viability of random-pattern skin flaps in the rat. These deleterious effects can be avoided if skin flaps are raised 2 weeks after cessation of nicotine treatment. This low-dose nicotine treatment does not cause histologic damage to the microvasculature. Other pathogenic mechanisms of nicotine-induced skin flap ischemia are discussed.

Role of noradrenaline in the pathogenesis of skin flap ischemic necrosis in the pig

Clinically, ischemic necrosis is one of the most common complications in skin flap surgery, but the etiology is still unclear. The objective of the present experiments was to study the important role of the locally released noradrenaline in the pathogenesis of ischemic necrosis in acute and delayed random pattern skin flaps (4 × 10 cm) raised on both flanks of the pig. In Experiment 1, it was observed that 93, 96, and 94% of the skin contents of noradrenaline were depleted in skin flaps delayed for 2, 4, and 14 days, respectively, compared to the acute skin flaps ( n = 8) raised in the same pig. Although the maximum depletion of noradrenaline in the delayed flaps occurred within 2 days of delay, significant ( P < 0.001) increase in the length of dye penetration in the delayed skin flaps was seen after 2 days of delay, compared to the acute skin flaps ( n = 12). In Experiments 2 and 3, 5 days of intravenous phenoxybenzamine treatment, starting 2 days preoperatively and at the doses of 0.25, 0.5, 1.0, or 1.5 mg/kg/day, did not have any significant effect on the skin blood flow ( n = 24) or viability (1 mg/kg/day; n = 32) in the acute skin flaps compared with the saline-treated control. Similarly, 5 days of intravenous phentolamine treatment (5 mg/kg/day) also did not have any significant effect on the skin blood flow ( n = 24) or viability ( n = 32) of acute skin flaps compared with the control. These results indicate that the hyperadrenergic state of the skin per se is unlikely a direct principal cause of skin flap ischemic necrosis in the pig.

Pharmacological augmentation of skin flap viability: a hypothesis to mimic the surgical delay phenomenon or a wishful thought.

The importance of the research in skin flap pharmacology is two-fold. First, observations made from the vasoactive drug actions in the vasculature of skin flaps can provide insight into the regulatory mechanism of cutaneous circulation and the pathophysiology of ischemic necrosis in skin flap surgery. Second, there is the possibility that the aforementioned information may eventually contribute to the development of a drug treatment for the augmentation of skin blood flow and viability in acute skin flaps (i.e., to mimic the surgical delay mechanism). To this end, the objectives of this article are: (1) to present a brief review of the recent research progress in the pharmacological treatment of ischemic skin necrosis in experimental flap surgery, and (2) to attempt to identify the future directions and important areas of research to be pursued in the pharmacology of skin flaps.

Design of skin flaps with a new technique using templates.

Patterned templates were constructed to assist in planning, performing, and teaching skin flap surgery. Templates can be used to design geometrically accurate flaps and to consider different flap orientation strategies. They can be used to align flap tension forces in proper relationship with relaxed skin tension lines.

Dose and time effects of nicotine treatment on the capillary blood flow and viability of random pattern skin flaps in the rat

The deleterious effects of nicotine treatment on skin haemodynamics and survival of 4 × 10 cm acute random pattern skin flaps constructed on the dorsum of the rat were studied. Rats were injected subcutaneously with 0.2 ml of saline containing varying doses (0, 1, 2, 4 or 8 mg kg −1; bid) of nicotine for 5 weeks, starting 4 weeks before flap surgery. It was observed that nicotine treatment at the dose of 2 mg kg −1 (bid), or higher, significantly (p < 0.05) decreased the length and area of skin flap survival compared with the control. This dose of nicotine treatment also significantly (p < 0.05) decreased the capillary blood flow and distal perfusion in the skin flaps compared with the control. However, the detrimental effect of nicotine treatment on the survival of acute random pattern skin flaps was not seen if the treatment was started 2 instead of 4 weeks preoperatively. It is concluded that nicotine may cause hypoperfusion and necrosis in acute random pattern skin flap surgery, and the deleterious effects are time-dependent.

Pharmacologic Manipulation of the Microcirculation in Cutaneous and Myocutaneous Flaps in Pigs

The vascular effects of isoxsuprine, diazoxide, and isoproterenol were studied in arterial buttock flaps and latissimus dorsi myocutaneous flaps in pigs. Capillary blood flow to the skin and muscle of these flaps was measured by the radioactive microsphere (15-mu diameter) technique 6 hours postoperatively under pentobarbital anesthesia. It was observed that isoproterenol, a beta-adrenergic receptor agonist, was not effective in augmentation of skin blood flow in the arterial buttock flaps. However, isoproterenol significantly increased capillary blood flow to the arterialized portion of latissimus dorsi myocutaneous flaps compared with controls. Isoxsuprine and diazoxide (vascular smooth muscle relaxants) significantly (p less than 0.05) increased total capillary blood flow to the skin of arterial buttock flaps and to the skin and muscle of the latissimus dorsi myocutaneous flaps. However, the increase in capillary blood flow occurred mainly in the arterialized portion of these flaps. The capillary blood flow, which was supplied by the small arteries in the distal portion of the arterial buttock and latissimus dorsi flaps, was not increased by treatment with isoxsuprine or diazoxide. Therefore, there was also no increase in the maximum distance of capillary blood flow from the pedicle to the distal end of the flaps. These observations led us to hypothesize that different sizes (diameters) of arteries in the skin and muscle have different reactivity (or sensitivity) to vasodilatory drugs. In the present experiment, the large dominant artery of the arterial buttock and latissimus dorsi flaps responded to isoxsuprine or diazoxide (vascular smooth-muscle relaxants), resulting in an increase in blood supply to the capillaries in the proximal portion of the flaps. On the other hand, the small arteries in the distal portion (random portion) of these flaps were not sensitive to isoxsuprine or diazoxide. Therefore vasodilation did not occur, and there was no increase in blood supply to the capillaries in the distal portion of arterial buttock and latissimus dorsi flaps. This explanation also lent support to our previous report that treatment with isoxsuprine did not augment skin viability in the distal portion of arterial buttock and latissimus dorsi flaps. It is suggested that research in pharmacologic manipulation of skin blood flow and viability in skin flap surgery should emphasize the sensitivity of small arteries to various drug actions.(ABSTRACT TRUNCATED AT 400 WORDS)