Effect of clamp versus anastomotic-induced ischemia on critical ischemic time and survival of rat epigastric fasciocutaneous flap

BACKGROUND: There are many models used to explore ischemic-related phenomena. The rat epigastric fasciocutaneous flap model is the one most commonly used. Critical ischemic time is the maximum ischemic insult that tissue can undergo and still remain viable. Experimentally, ischemia is induced either by clamping the vascular pedicle or by dividing the pedicle then performing microvascular arterial and venous anastomosis. We sought to determine what effect the different methods of inducing ischemia have on the critical primary ischemic time and, thus, flap survival. METHODS: A right 3 cm x 6 cm groin flap based on the inferior epigastric vessels was raised in each rat. Ischemic times of 4, 6, 8, or 10 hours were induced either by placing temporary occlusion clamps on each vessel of the vascular pedicle (island pedicle group) or by ligation and division of the pedicle with subsequent microvascular anastomosis (free flap group). Survival was assessed at 7 days. RESULTS: The primary ischemic time at which one half of free flaps are predicted to die was calculated to be 7.60 hours, compared with 6.09 hours for the island pedicle flaps (p<.05). CONCLUSIONS: Fasciocutaneous flaps undergoing ligation and anastomosis are more resistant to ischemia than are those undergoing clamping of the pedicle. Possible etiologic factors responsible for this experimental finding are discussed.     

Beneficial effect of hyperbaric oxygen on island flaps subjected to secondary venous ischemia

The potential for hyperbaric oxygen therapy (HBO) to decrease the untoward effects of a secondary ischemic event was studied in the rat superficial epigastric flap model. The secondary venous ischemic flap was created by cross-clamping the vascular pedicles for 2 h. Twenty-four hours later, the flap was reelevated and the venous pedicle was occluded for 5 h. Thirty-two rats were divided into three groups. In experimental group 1, animals received HBO treatment immediately prior to the initial flap elevation and ischemia at 2 atmosphere pressures for 90 min. In experimental group 2, the rats underwent a similar course except for a second 90-min HBO course immediately prior to the secondary venous occlusion. The rats without HBO therapy were used as controls. The results showed that all control flaps were nonviable at 1 week by clinical inspection and fluorescein injection. Complete flap survival occurred in 20% of group 1 flaps and 30.8% of group 2 flaps. Partial flap survival occurred in the rest of the flaps in these two groups, with mean survival areas of 48% and 55%, respectively. In conclusion, HBO treatments significantly increase the survival of flaps subjected to a secondary ischemia, even if administered before the primary ischemia. Administering HBO prior to secondary venous ischemia was marginal, which may be due to the effect of O(2) given by HBO not lasting longer than 5 h.     

The effect of time of vascular island skin flap elevation on tolerance to warm ischemia

The effect of time of vascular island skin flap elevation on tolerance to a subsequent 12-hour period of warm ischemia was studied. Sixty rats were separated into five equal groups; the rat epigastric island flap was used as the model. In group 1 flaps were elevated and immediately subjected to 12 hours of complete ischemia by application of microvascular clamps to both artery and vein of the pedicle. In group 2 the flap was elevated, and after 12 hours of recovery ischemia was induced for 12 hours. Groups 3 to 5 were similar to group 2 except that the time interval between initial elevation and subsequent ischemia varied: 24 hours for group 3; 72 hours for group 4; 144 hours for group 5. Necrosis was evaluated on postoperative day 7. Those flaps elevated 24 hours before ischemic insult (group 3) had significantly better survival than all other groups (p less than 0.025 at least). There were no significant differences between the other groups. Flap elevation 24 hours before a complete ischemic episode significantly increased tolerance to ischemia. Elevating a flap earlier or later than 24 hours did not have any significant benefit.     

A novel model for supermicrosurgery training: the superficial inferior epigastric artery flap in rats

The purpose of this study was to determine the usefulness of a new flap model, the superficial inferior epigastric artery (SIEA) flap for supermicrosurgical training. Experimental groups were randomly divided into three groups of 10 rats each. In each group SIEA flaps were elevated and then returned to their original locations with or without vascular anastomosis of the superficial inferior epigastric vessels. Group 1: free SIEA flap, group 2: free SIEA flap with 1 hour ischemia time, group 3: free SIEA flap with 4 hours ischemia time, group 4: SIEA flap without vascular anastomosis. The viability rate was 80% with group 1, 50% with group 2, and 40% with group 3. All nonvascularized flaps (group 4) underwent complete necrosis. These findings suggest that preservation of blood flow in a flap has a beneficial effect on the prevention of microthrombosis in the subcutaneous capillary network of the skin and increases the flap survival rate. The SIEA flap with preserved circulation is an ideal model for developing supermicrosurgical skills.     

The effect of ischemic preconditioning on secondary ischemia in skin flaps

Ischemic preconditioning is a useful manipulation to reduce the undesirable effects of ischemia. The beneficial results of this phenomenon against ischemia-reperfusion have been seen in different flap models; however, all these studies have focused on primary ischemia. In this study, we investigated the effects of ischemic preconditioning on secondary ischemia in a skin flap model. We used the 6- x 3-cm-sized epigastric skin flap in 40 Wistar rats. In all animals, primary global ischemia of 2 hours was followed by 4 hours of either arterial or venous secondary ischemia 24 hours after the primary ischemia and ischemic preconditioning (IP) was tested in this protocol. Ischemic preconditioning was performed by 2 cycles of 15 minutes of repeated ischemia/reperfusion periods. The animals were allocated into 4 groups: group 1 (n = 10 animals): primary ischemia (2 hours) + secondary arterial ischemia (4 hours); group 2 (n = 10 animals): IP + primary ischemia (2 hours) + secondary arterial ischemia (4 hours); group 3 (n = 10 animals): primary ischemia (2 hours) + secondary venous ischemia (4 hours); group 4 (n = 10 animals): IP + primary ischemia (2 hours) + secondary venous ischemia (4 hours). Flap viability was assessed 1 week after the surgical procedure, and surviving flap area was recorded as a percentage of the whole flap area. Group 1 was compared with group 2, and group 3 was compared with group 4 to evaluate the effects of ischemic preconditioning against secondary arterial and venous ischemia. t test and Mann-Whitney rank sum tests were used for statistical analysis. There were statistical differences both between groups 1 and 2 and groups 3 and 4. The results revealed that ischemic preconditioning was an effective procedure to reduce the flap necrosis as a cause of secondary ischemia in skin flaps.     

Further investigation of secondary venous obstruction.

The first ischemic insult a tissue suffers is primary (1 degree). A second ischemic episode, such as thrombosis after free tissue transfer may be regarded as secondary (2 degrees) ischemia. The current study investigated 2 degrees ischemia in rodent epigastric flaps. Flaps were elevated in 50 Sprague-Dawley rats: group 1 had 5 hours 1 degree venous ischemia induced by placement of microvascular clamps; group 2 was like group 1, except venous continuity was re-established by venous anastomosis after resection of the venous segment previously microclamped; group 3 had 15 minutes of 1 degree ischemia, 24 hr later 5 hr of 2 degrees venous ischemia was induced by placement of microvascular clamps; group 4 was like group 3, except the venous segment was excised. Necrosis was evaluated on postoperative day 7. Both secondary ischemic groups had significantly less flap survival than the corresponding primary ischemic groups (P less than 0.001 for both). Resection of a portion of the vein and subsequent microanastomosis did not reduce flap survival (NS). Secondary venous ischemia of 5-hr duration is poorly tolerated by rodent skin flaps. There was no difference in flap survival in those flaps whose veins were clamped for 5 hr compared to those flaps whose clamped venous segments were resected and re-anastomosed.     

Secondary venous ischemic injury associated with neutrophil infiltration and lipid peroxidation: amelioration of injury by cyclosporin A in a rat inguinal island flap

Secondary venous ischemia caused by anastomotic failure is one of the major causes of failure after free tissue transfers and replantations. The effects of cyclosporin A (CsA) on secondary ischemic injury associated with neutrophil infiltration and lipid peroxidation were evaluated in a rat inferior epigastric island skin flap model. Primary ischemia was produced by arteriovenous occlusion for 2 hours. Twenty-four hours later, secondary venous ischemia was produced by 5 hours of venous occlusion. Nonischemic (n = 5), primary ischemic (n = 5), and secondary ischemic control groups (n = 10), and four treatment groups (n = 10) were created. Treatment groups received either 15 or 30 mg per kilogram per day oral CsA for 3 days before flap elevation, or 15 or 30 mg per kilogram intravenous CsA at 4 hours of secondary venous ischemia. Flap survival area, malondialdehyde (MDA) content, and myeloperoxidase (MPO) activity were assayed for each group. The mean flap survival area of the high-dose posttreatment group was significantly higher than the secondary ischemic control group (29% +/- 39% vs. 3% +/- 8%; p < 0.05, Student's t-test). The MDA and MPO levels of each treatment group were significantly lower than the secondary ischemic control group at hours 1 and 24 (p < 0.0001, Student's t-test). The lowest MDA and MPO levels were achieved in the high-dose posttreatment group. Results suggest that CsA may improve flap survival after secondary venous ischemia by attenuating neutrophil infiltration and by reducing lipid peroxidation.     

Effect of allopurinol,superoxide-dismutase,and hyperbaric oxygen on flap survival

The effect of allopurinol, superoxide-dismutase, and hyperbaric oxygen was compared on axial pattern skin flap survival. An abdominal flap based on the inferior epigastric pedicle was raised in rats for this purpose. Three experimental groups were studied. In the first group, adult male Wistar rats received 50 mg/kg I.P. of allopurinol. The second received 20,000 I.U./kg of superoxide-dismutase. The third group was submitted to hyperbaric oxygen therapy. The flaps were exposed to 8-h warm ischemia. Flap survival was evaluated on postoperative day 7. All flaps survived, and the mean survival areas were 63.53%, 83.03%, and 55.98%, respectively, in the allopurinol, superoxide-dismutase, and hyperbaric groups. The percentage of flap necrosis was significantly smaller in all experimental groups when compared to controls (P < 0.05). It was clear that the superoxide-dismutase group had better results on axial pattern ischemic skin flap survival, under the tested conditions. The tested methods improved flap survival to ischemic injury, and the flap designed is a reliable model for further investigations.     

The effect of hyperbaric oxygen on ischemia-reperfusion injury: an experimental study in a rat musculocutaneous flap

The effect of hyperbaric oxygen is known to increase survival of ischemic tissue but its mechanism is not fully understood. The purpose of this study was to evaluate the effect of hyperbaric oxygen on a rat musculocutaneous flap versus ischemia-reperfusion injury, focusing on the mechanism involving the expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) of endothelial cells and CD18 of neutrophils. A transverse rectus abdominis musculocutaneous (TRAM) flap (6 x 5 cm) supplied by a single superior epigastric vascular pedicle was elevated in 100 Sprague-Dawley rats. The rats were divided into 4 groups: group 0, sham (n = 10); group I, 4 hours of ischemia followed by reperfusion (n = 30); group II, 4 hours of ischemia and hyperbaric oxygen (100% oxygen, 2.5 atm absolute, during the last 90 minutes of ischemia before reperfusion) followed by reperfusion (n = 30); and group III, 4 hours of ischemia followed by reperfusion and hyperbaric oxygen (100% oxygen, 2.5 atm absolute, after reperfusion for 90 minutes; n = 30). The study consisted of gross examination for flap survival, histology, immunohistochemical staining, myeloperoxidase assay, flow cytometric study of CD18, and Northern blot analysis on ICAM-1 messenger ribonucleic acid expression. Gross measurement of the flap showed increased survival in groups II and III compared with group I (P < 0.05). The leukocytes adherent to the endothelium were counted at 24 hours and on day 5. Group I leukocytes were significantly increased compared with groups II and III (P < 0.05). The myeloperoxidase assay of TRAM flaps at 24 hours revealed a significant increase in group I compared with groups II and III (P < 0.05). The expression of CD18 was similar between groups I, II, and III. Immunohistochemical staining for ICAM-1 and Northern blot analysis on ICAM-1 messenger ribonucleic acid showed decreased expression in groups II and III compared with group I. Throughout the analysis, groups II and III did not show any significant differences. These results suggests that hyperbaric oxygen reduces the accumulation of leukocytes in the TRAM flap, but not enough to prevent adhesion of neutrophils on endothelial cells; ischemia-reperfusion injury increases the expression of CD18 and ICAM-1 and causes increased adhesion of leukocytes on the endothelium; hyperbaric oxygen does not alter the expression of CD18 but decreases the expression of ICAM-1; and the point of application for hyperbaric oxygen, whether applied before or after reperfusion, did not show any differences in outcome. In conclusion, the application of hyperbaric oxygen against ischemia-reperfusion injury increases flap survival and the beneficial effect may be explained by a protective mechanism involving downregulation of ICAM-1 on endothelial cells.     

Postischemic flap washout with hydroxyethyl starch (HAES) and its beneficial effect on the no-reflow phenomenon in rat skin island flaps

This study investigated the possible effect of hydroxyethyl starch (HAES) as a postischemic perfusion washout on survival of skin flaps. Forty-eight, male, Sprague-Dawley rats were used in this experiment. A 4×6 cm unilateral island skin flap based on the superficial inferior epigastric artery and vein was raised. The femoral neurovascular bundle supplying the flap pedicle was also dissected free. The flaps were divided into four groups, each consisting of 12 rats. Group 1 (Nonishemic control); Group 2 (Control) – no perfusion washout; Group 3 (Saline) – postischemic washout with normal saline solution; Group 4 (HAES) – postischemic washout with hydroxyethyl starch 10% (HAES) solution. The flaps were subjected to 11 hours of warm ischemia. Thirty minutes prior to the completion of the ischemic period, the flaps were perfused with normal saline solution in group 3 and with HAES in group 4. The percentage of flap survival was assessed on postoperative day 7. Statistical analysis was performed using the Student’s t-test. Flap survival rates for Group 4 (HAES) were significantly greater than Group 2 (Control nonperfusion washout) and Group 3 (saline solution) (p<0.001). This is the first study to investigate the effect of HAES on skin flap survival based on the results, HAES solution may be useful in clinical practice. Received: 6 August 1997 / Accepted: 11 December 1997     

Protective effect of a novel NO-donor on ischemia/reperfusion injury in a rat epigastric flap model

An altered metabolism of endothelial cell-derived nitric oxide has been implicated in the microvascular dysfunction associated with ischemia/reperfusion. The objective of this study was to examine whether S-nitroso human serum albumin, a novel nitric oxide-donor, improves flap viability and whether it influences edema formation after prolonged ischemia when administered prior to and in the initial phase of reperfusion. Denervated epigastric island skin flaps were elevated in 30 male Sprague Dawley rats, rendered ischemic for 8 hours, subsequently reperfused and further observed for either 3 hours (acute) or 7 days (chronic). In the sham rats (n = 6), skin flaps were elevated only. Starting 1 hour prior to reperfusion, S-nitroso human serum albumin (n = 12) or human serum albumin (n = 12) as placebo was infused systemically for 2 hours. In the chronic model, flap necrosis as well as viable flap size was evaluated after 7 days of reperfusion in six rats per group, comparing to sham rats. In the acute model, edema formation was evaluated after 3 hours of reperfusion in six rats per group. Administration of S-nitroso human serum albumin significantly decreased flap necrosis from 18.1 +/- 15.6% in the human serum albumin group to 2.1 +/- 1.5% in the S-nitroso human serum albumin group, which was similar to the sham group (2.5 +/- 4.2%). Viable flap size (sham 13.4 +/- 1.6 cm2) was also significantly improved in the S-nitroso human serum albumin group (10.1 +/- 1 cm2) versus the human serum albumin group (7.0 +/- 2.2 cm2). There was no significant difference between the groups regarding postischemic edema formation. These results show that administration of S-nitroso human serum albumin prior to and in the initial phase of reperfusion significantly improves flap viability after 7 days but does not influence early observable edema formation. These findings support the role of nitric oxide as an important mediator in the protection against skin flap ischemia/reperfusion injury.     

Ischemic preconditioning of a rat adipomusculocutaneous flap: which duration of ischemia/reperfusion works best?

In this study a comparison was made to the efficacy of three cycles of various duration of ischemic preconditioning (IPC) on flap survival after the critical ischemic time. Method: In the first study, 20 Sprague-Dawley rats were used (6 groups of rats; flap ischemia ranging from 6 to 14 h) to determine the critical ischemia time for the rat groin flap (6×3 cm). In the second study the rats (n=31 were divided into nine groups; ischemia and reperfusion times being 5, 10 or 15 min) a groin flap was elevated. Thereafter IPC was induced to the flap by clamping its pedicle prior to the critical ischemic time (14 h). Three cycles of IPC were applied. After seven days, the flap was retraced for viability assessment and the surviving flap area was calculated with planimetry. Results: Without pretreatment with IPC flap survival after 8, 10, 12, 13, and 14 h global ischemia was respectively 100%, 77±13%, 78±15%, 42±16%, and 2±4%. When the flaps were treated with three cycles of IPC before 14 h global ischemia the significant flap survival was noted in the 10/5 min and 15/10 min IPC groups (p<0.05). Overall, the 5 min reperfusion groups increased flap survival (38±26%; p<0.05), and had fewer total flap losses (2/9) than the 10 or 15 min reperfusion groups. Only if ischemia time was longer than reperfusion time the flaps had increased survival area (40±22%, p<0.05). Conclusion: This study demonstrated the efficacy of IPC to improve the viability of a composite flap even after a long critical ischemic time. The optimal IPC duration was 10/5 min combination, yet the 15/10 schedule was also acceptable. Received: 20 May 1998 / Accepted: 20 July 1998     

The effect of trimetazidine on the survival of rat island skin flaps subjected to ischemia-reperfusion injury

The effect of trimetazidine (TMZ) on flap ischemia-reperfusion injury was investigated in rat inferior epigastric artery flaps. Twenty-six rats, divided into four experimental groups-nonischemic group (group 1, N = 5), ischemic control group (group 2, N = 7), preischemic TMZ-treated group (group 3, N = 7), and postischemic TMZ-treated group (group 4, N = 7)-were used. Rat inferior epigastric artery flaps were rendered ischemic by occluding the feeding femoral artery, and they were reperfused by releasing the clamps after 11 hours in groups 2 through 4. Group 3 rats were given TMZ (3 mg per kilogram, intravenously) diluted in saline before application of the clamp, and group 4 rats were given TMZ before clamp removal. Flap survival was scored on postoperative day 8. All flaps in the nonischemic control group (group 1) survived completely. The ischemic control group (group 2) demonstrated a 6.3 +/- 4.3% survival area. In the preischemic TMZ group (group 3) the mean survival area was 76.9 +/- 6.1%, and in the postischemic TMZ group (group 4) it was 76.8 +/- 5.6%. TMZ-treated flaps showed a significant increase in survival area regardless of the time of administration (p = 0.001, group 3 vs. group 2; p = 0.001, group 4 vs. group 2). This finding suggests that TMZ has a beneficial effect on the prevention or treatment of arterial ischemic flaps.     

Extracorporal shock wave may enhance skin flap survival in an animal model.

Several methods have been used in an attempt to increase blood supply and tissue perfusion in ischemic tissues. The authors investigated the effect of extracorporal shock wave (ESW) treatment on compromised skin flaps. For this purpose, the epigastric skin flap model in rats, based solely on the right inferior epigastric vessels was used. Twenty male Sprague-Dawley rats were divided into two groups (ESW-group, Control group) of 10 rats each. The ESW-group was administered 2500 impulses at 0.15 mJ/mm(2) immediately after surgery, whereas, the control group received no treatment. Flap viability was evaluated on day 7 after the operation. Standardised digital pictures of the flaps were taken and transferred to the computer, and necrotic zones relative to total flap surface area were measured and expressed as percentages. Overall, there was a significant reduction in the surface area of the necrotic zones of the flaps in the ESW group compared to the control group (ESW group: 2.2+/-1.9% versus control: 17.4+/-4.4% (p < 0.01). In this study, the authors demonstrated that treatment with ESW enhanced epigastric skin flap survival, as confirmed by the significant reduction of necrotic flap zones. ESW treatment seems to represent a feasible and cost effective method to improve blood supply in ischemic tissue.     

皮瓣受区床与缺血-再灌注皮瓣成活的关系

目的 :探讨皮瓣受区床对缺血 -再灌注皮瓣成活的影响 ,重视受区床的营养性作用。　方法 :40只大鼠分成 A组 (皮瓣下不置硅胶膜 )、 B组 (皮瓣下置硅胶膜后再缝合 )。阻断腹壁浅血管 1h、 6 h、 10 h及完全切断腹壁浅血管 ,观测不同时段皮瓣温度及组织病理改变 ,7天时计算皮瓣成活面积。　结果 :皮瓣温度、皮瓣成活面积及组织病理学改变阻断血管1h A、 B组无明显差别 ,阻断 6 h、 10 h及完全切断血管两组间有显著差别。 A组阻断 10 h与完全切断血管两组间皮瓣成活面积很相近。 A组完全切断血管后真皮下组织见白细胞大量聚积。　结论 :皮瓣受区床对缺血 -再灌注皮瓣成活起营养作用。白细胞可损害这种营养性作用。     

The Effects of Increased Ischemic Times on Adipose Tissue: A Histopathologic Study Using the Epigastric Flap Model in Rats

Little study has investigated the ischemic injury of mature adipocytes. This study researched the effects of different ischemic times on fat histology the 7th postischemic day in a rat epigastric flap model. For this study, 24 rats were randomly divided into four groups subjected, respectively, to 1, 2, 3, and 4 h of ischemia. The most severe inflammation and fat necrosis scores were seen in groups 3 and 4 (p < 0.05). According to the findings of this study, it is possible to say that fat tissue undergoes a gross necrosis after 3 or more hours of ischemia. After that ischemic time, the necrotic volume of fat tissue subjected to ischemic insult does not increase with increased ischemic time.     

Angiogenic effects of injected VEGF165 and sVEGFR-1 (sFLT-1) in a rat flap model

BACKGROUND: Injections of single-dose vascular endothelial growth factor (VEGF)(165) have been advocated as a therapeutic tool for angiogenesis in ischemic flaps. We challenged this thesis by employing both VEGF(165) and vascular endothelial growth factor receptor-1 (VEGFR-1) (for competitive inhibition of VEGF signal transduction) in different experimental settings of an ischemic rat flap model. MATERIAL AND METHODS: 80 isogenic rats were divided in two groups of 40 animals (groups 1A-1D and 2A-2D). The ischemic target was a 7 x 7-cm epigastric island flap, based on the right inferior epigastric pedicle. Group 1 received flap treatment 1 week prior to flap elevation by test substance injection into its flap panniculus carnosus: 1 ml NaCl 0.9% (1A), 1 ml Dulbecco's modified Eagle's medium (1B), 1.0 microg VEGF(165) (1C), and 10 microg sFLT-1 with 1.0 microg VEGF(165) (1D). sFLT-1 is a soluble receptor for VEGF and is able to prevent VEGF signaling through the cell surface receptor. Group 2 had the same flap treatment at the day of flap elevation. RESULTS: In group 1C we found the most vital flap tissue, without reaching significance. Compared with group 1D, however, significantly more flap tissue maintained vital. In groups 2A-2D, no significant results were found with respect to flap survival. CONCLUSIONS: Local application of single-dose VEGF(165) 1 week prior to ischemia dose not have significant clinical angiogenic effects. In this experimental setting, VEGF(165)-induced angiogenic effects can be significantly inhibited by adding sFLT1 in vivo. A single-dose of VEGF(165) under ischemic conditions causes no significantly better flap survival in this model.     

Effect of surgical denervation on the viability of inferior epigastric neurovenous flaps in the rat

The purpose of this study was to examine how the inferior epigastric neurovenous flap in the rat reacts to surgical denervation. The survival of a denervated flap was compared with that of an innervated flap. A 2 x 2-cm flap was raised in 30 female Wistar rats assigned randomly to six groups of 10 rats each: group 1, innervated neurovenous flap; group 2, denervated neurovenous flap, acute model; group 3, denervated neurovenous flap, chronic model; group 4, innervated inferior epigastric island flap; group 5, denervated inferior epigastric island flap, acute model; and group 6, control, composite graft. Acute denervation produced a significant decrease in the survival of the inferior epigastric neurovenous flap (p < 0.05). The surviving area of the innervated flaps decreased from 94+/-14% (mean +/- standard deviation) to 16+/-34% by acute denervation. Chronic denervation was effective in decreasing flap necrosis in these flaps (survival, 99+/-5%). There were no differences between the average viable area of the standard inferior epigastric flap in the denervated and innervated groups.     

Correlation of viability and laser Doppler flowmetry in ischemic flaps

Microvascular blood flow was measured by a laser Doppler flowmeter in rabbit epigastric island flaps made ischemic at 37 degrees C for either 6.5 hr (Group 1; n = 13) or 17.5 hr (Group 2; n = 4). Contralateral flaps raised without ischemia were used as controls. The survival of ischemic flaps in these groups at 7 days was 69 and 0%, respectively. After 6.5 hr of ischemia, microvascular blood flow in the ischemic flap was approximately 20% below that in the control flap for the first 3-4 days postoperatively, presumably reflecting ischemic damage to parts of the cutaneous microcirculation; thereafter, flow was not significantly different from controls up to 7 days postoperatively. Failed 6.5-hr ischemic flaps had initial sluggish blood flow which slowed to zero usually within 4 days postoperatively. After 17.5 hr ischemia, negligible microvascular flow was detectable postoperatively. Failure in the microcirculation as detected by the flowmeter occurred well in advance of any noticeable physical changes in the flap. It is concluded that the percentage ischemic flap flow of control flap flow for each animal (at any selected time up to 24 hr after revascularization) reliably predicts the viability of the flap after 7 days.     

天然水蛭素对大鼠缺血皮瓣血管生成作用的Micro-CT观察

目的通过Micro-CT及三维重建技术观察天然水蛭素对大鼠缺血皮瓣血管生成的影响。方法选取32只成年SD大鼠,在其背部制备一8.0cm×1.8cm大小的缺血皮瓣模型,然后随机分为水蛭素组和对照组(n=16)。水蛭素组术后即刻和术后3 d内每天皮下注射天然水蛭素0.3 mL(含天然水蛭素6 ATU),对照组皮下注射等量生理盐水。术后6 d,大体观察皮瓣成活情况并测定皮瓣成活率,取材行HE染色观察皮瓣组织学变化,行Micro-CT三维重建观察并测量皮瓣血管容积、长度及数量。结果术后两组大鼠均存活至实验完成,无感染发生。术后6 d,两组皮瓣远端均发生不同程度坏死,水蛭素组皮瓣成活率为72.11%±8.97%,显著高于对照组的58.94%±4.02%,差异有统计学意义(t=3.280,P=0.008)。组织学观察示水蛭素组较对照组组织结构层次更清楚,有较多微血管生成,炎症反应及炎症细胞浸润更轻。Micro-CT三维重建示水蛭素组皮瓣血管更多、更加密集;血管容积、长度及数量均显著大于对照组(P<0.05)。结论天然水蛭素可减轻组织炎症反应、促进缺血皮瓣血管的新生与再通,从而提高皮瓣成活率。