The effect of low-molecular-weight heparin in the survival of a rabbit congested skin flap

Swelling and congestion of flaps are frequently seen postoperatively and can cause unexpected necrosis. According to previous reports, venous thrombosis seems to be a more frequent problem than arterial occlusion in both experimental and clinical surgery. Few satisfactory venous trauma models exist, and reports on experimental venous thrombosis are rare. The object of this study was to create a rabbit venous occlusion flap model and to evaluate the effect of low-molecular-weight heparin on this flap. Eight New Zealand rabbits were used in the pilot study, in which the ideal congested flap was investigated using a flap pedicle based on the central auricular artery with a skin pedicle 0, 1, 2, or 3 cm wide. The flap (3 x 6 cm) was designed on the central part of the left ear, and the central auricular vein and nerve, the former for venous return, were cut out at the base of the flap. The flaps with skin pedicles 0, 1, 2, or 3 cm wide showed mean necrosis length of 60.0, 9.3, 4.2, and 0.0 mm, respectively. The flaps with skin pedicles 0, 1, 2, or 3 cm wide showed mean necrosis of 100, 15.5, 7, and 0 percent, respectively. Therefore, the flap, based on a 1-cm-wide skin pedicle and the central auricular artery, was selected as an optimal congested flap model showing 15.5 percent necrosis. The congested flap was then elevated on the left ear of another 10 rabbits. Subcutaneous low-molecular-weight heparin (320 IU/kg) was administered immediately after surgery to five of the rabbits (the low-molecular-weight heparin group), and the remaining five were used as a control group. Fluorescein was injected 15 minutes after surgery to evaluate the circulatory territory of the flap, and the circulatory territory was measured 5 minutes after injection. The flaps were assessed 7 days after surgery by angiography, histology, and clinical findings. The circulatory territory was significantly greater in the low-molecular-weight heparin group (mean +/- SD, 39.2 +/- 3.0 mm) than the control group (mean +/- SD, 48.0 +/- 1.0 mm) (p < 0.001) assessed 7 days after surgery. The longest flap survival length in group A and group B ranged from 40 to 55 mm (mean +/- SD. 49.4 +/- 5.6 mm) and complete survival (mean +/- SD, 60.0 +/- 0.0 mm). The improvement in survival was statistically significant for group B compared with group A (p < 0.015). Histologic evaluation revealed moderate to severe venous congestion and inflammation in the control group, whereas there were minimal changes in the low-molecular-weight heparin group. Angiography of the flap revealed obvious venous occlusion in the periphery in the control group compared with the low-molecular-weight heparin group. The authors conclude that subcutaneous administration of low-molecular-weight heparin has a great potential to improve the survival length of a congested flap without major complications.     

The role of the large superficial vein in survival of proximally based versus distally based sural veno-neuro-fasciocutaneous flaps in a rabbit model

A sural veno-neuro-fasciocutaneous flap in the New Zealand White rabbit was developed, and the role of the large subcutaneous lesser saphenous vein was investigated in proximally based versus distally based flaps. Retrograde dye injection showed that the lesser saphenous vein in rabbits has many valves with strong resistance against reflux. Twenty rabbits were randomly allocated into four groups of 10 flaps each. Group I consisted of proximally based flaps with the lesser saphenous vein intact (outflow) in the veno-neuro-adipofascial pedicle. Group II also consisted of proximally based flaps but the lesser saphenous vein was ligated at 1 cm proximal to the pedicle. Group III consisted of distally based flaps with the lesser saphenous vein intact (inflow) in the veno-neuro-adipofascial pedicle. Group IV also consisted of distally based flaps, but the lesser saphenous vein was ligated at 1 cm distal to the pedicle. The results showed that the mean flap survival area in group I (88.8 percent) was statistically higher than that in group II (62.6 percent, p < 0.001), and was higher in group IV (55.5 percent) than in group III (22.7 percent, p < 0.01). However, group II and group IV had no significant difference (p > 0.05). This experiment demonstrated that flap viability is determined by its intrinsic vascularization, both arterial and venous. The large superficial subcutaneous vein has a positive role (venous outflow) in proximally based flaps but a negative role (venous inflow) in distally based flaps. If the effect of the large subcutaneous vein is excluded, distally based flaps are not inherently inferior to proximally based flaps.     

Experimental studies in the survival of venous island flaps without arterial inflow

The authors have studied the effects of various circulatory settings on flap survival. The dog model was used to study the survival of venous flaps without arterial inflow both as island and free flaps. Venous flaps were compared with arterial flaps without venous outflow and standard island flaps with arterial inflow and venous outflow. Attempts were made to study their vascular morphology and blood gas changes. The venous flaps without arterial inflow survived with normal hair growth and wound healing, as did the standard island flaps. These observations suggest that capillary diffusion can occur without the continuous flow of blood through a capillary. Several possible mechanisms to explain survival of the venous flaps without arterial inflow were discussed. These observations could be important in providing an animal model to study microcirculation and a possible new area for microsurgical transfer of a skin flap.     

Island rat groin flaps with twisted pedicles

Clinical attempts are made to avoid rotating a flap and twisting the pedicle for fear of perfusion compromise. Torsion of an island rat groin flap pedicle is not a well-recognized experimental entity. The authors describe the results of island flap rotation with pedicle twisting in the rat groin flap model. Forty male Wistar rats were randomly divided into four groups of 10 animals each. In each group, bilateral groin flaps were elevated; one flap was sutured in place without rotation and the contralateral flap was subjected to 180, 270, 360, or 720 degrees of rotation. Blood flow within the flaps was assessed by laser Doppler flowmetry, and flap edema and necrosis were determined 10 days postoperatively. No differences were noted between control flaps and those subjected to 180 and 270 degrees of rotation. Although flaps subjected to 360 degrees of rotation demonstrated a large amount of postoperative edema and congestion of the subcutaneous tissue with some histologic changes, all flaps in this group survived. Measured flap weights at death were different from those of controls. All flaps subjected to 720 degrees of rotation underwent ischemic necrosis. Because of the differences between human skin architecture and rat skin architecture it cannot be concluded that similar results would be observed in any human skin flap. There might be three important points arising from this study of unknowingly twisted island groin flap pedicles in the rat model: (1) twisting of less than 360 degrees has no effect on flap survival; (2) twisting of 720 degrees is always associated with skin flap necrosis; (3) twisting of 360 degrees, although associated with some changes, does not cause skin flap necrosis.     

Attempts to increase the surviving length in skin flaps by a moist environment.

A method of raising a random patterns flap on the back of a rat was used to study the relationship between the surviving length and distance of dye penetration. It was found that the intraoperative dye distance was an accurate predictor of survival length in the Control Group. The effects of dressing were evaluated against the controls. An apparently significant increase in the survival length (beyond the dye distance) was seen with the "tunnel procedure" we used. It is suggested that a moist environment will favor survival of that portion of a flap where necrosis is usually seen when no dressing is used.     

Perforator-based flap in rats: a new experimental model.

A new type of flap, the perforator-based flap, has been described in the last decade. It has been used successfully as a pedicle or free flap by many plastic surgeons. There is no animal model for research, although these flaps have gained popularity in clinical use. We created a perforator-based flap model in the rat (a perforator-based flap group and two control groups; 10 rats in each group) and evaluated the survival characteristics of the new flap. The abdominal skin flap was elevated based on the second perforator of the right superior deep epigastric artery and then sutured to its original bed. In the first control group, the same flap was elevated with a subcutaneous pedicle without any perforator; in the second control group, a right-sided, random-pattern pedicle abdominal skin flap with the same dimensions and location was elevated and sutured to its original bed. Flap survival was studied, and microangiography and histologic studies were performed. The amount of viable skin in the three groups was compared 1 week later. The area of surviving skin paddles in the experimental group ranged from 74 to 83 percent; in the first control group, it was 0 percent; and in the second control group, it ranged from 29 to 44 percent (p < 0.001 and p < 0.001, respectively). There was a predictable and constant area of necrosis in the model.The results of this study demonstrate that most of the abdominal skin of the rat can survive on the basis of a single musculocutaneous perforator vessel. This flap can be easily elevated, and it can be used as a reliable model for flap research.     

A new flap design: neural-island flap

This report introduces the "neural-island flap" concept, which represents a consistent and reliable skin flap design supplied only by the intrinsic vasculature of a cutaneous nerve. In this study, the lateral femoral cutaneous nerve was selected as the pedicle of the neural-island flap, and a standard skin flap, which is the territory of the accompanying vessels (i.e., iliac branches of the iliolumbar artery and vein), was elevated on the lower dorsal region of the rats. In a total of 92 Wistar rats, three experiments were performed. In part I (n = 24), the vascular anatomy of the lateral femoral cutaneous nerve was established by the methods of dissection, microangiography, nerve mapping, perfusion with colored latex and India ink, and histologic analysis. In part II (n = 46), the role of the cutaneous nerve in supporting an acutely elevated skin flap was explored by creating five flap groups as follows: group 1, conventional flap (artery, vein, and nerve intact); group 2, neural island flap (only the nerve intact); group 3, neurocutaneous flap (vein and nerve intact); group 4, denervated flap (artery and vein intact); and group 5, skin graft. In part III (n = 22), the role of a preliminary surgical delay procedure to augment the survival of the neural island flap was investigated. Results of the anatomic studies indicated a consistent perineural vasculature by the accompanying iliolumbar artery. Skin flaps survived totally in groups where the artery and vein were intact, whereas mean survival rates for the neural island flap and the neurocutaneous flap were 38.2 +/- 3.1 percent and 44.5 +/- 3.8 percent, respectively (p > 0.05). Results of part III of the experiment demonstrated a significantly higher survival for the delayed neural island flap (94.5 +/- 5.5 percent) compared with the acutely elevated neural island flap (p < 0.05). The perineural and intraneural vessels were found to be greatly dilated after a delay procedure, demonstrated by direct observation, microangiography, histologic analysis, dye injection study, and scanning electron microscopy. On the basis of this promising series of experiments, a clinical technique was developed using the sural neural-island flap. The flap was used to reconstruct lower extremity defects in four cases. A delay procedure was accomplished in the first stage by elevating a fasciocutaneous flap from the midcalf region based on a posterior skin bridge and the sural nerve. After a 2-week delay period, a sural neural-island flap was created based on the nerve and transposed to the defect. Flap survival was complete in all cases, with a satisfactory result. The authors conclude that this report proves for the first time that a robust and reliable skin flap can be created pedicled only by the intrinsic vasculature of a cutaneous nerve, after a proper surgical delay. The so-created neural-island flap design offers two novel advantages: (1) a very narrow pedicle and (2) a pedicle without any restriction to a specific pivot point, in addition to the previously described unique advantages of preservation of a major artery and avoidance of microvascular anastomoses.     

The minimal requirement of circulation for survival of undelayed and delayed flaps in rats

In an attempt to clarify the delay phenomenon, the regional blood flow was measured in 10 undelayed flaps and 65 delayed flaps in rats by the clearance method with the electrolytically generated hydrogen. The ultimate purpose of this study was to establish the minimal requirement of blood flow for flap survival. The dye distance and the survival length were also measured. Blood flow in the flap increased with the delay period. Elongation of the survival length and the dye distance corresponded well to the circulatory enhancement. The present findings support the theory that delay improves blood circulation. The distance from the base to the 0.04-ml flow point was found to be highly correlated with survival length in the delayed groups as well as in the undelayed group. Based on the results, the minimal requirement of circulation for flap survival was assumed to be approximately 0.04 ml/min per gram of tissue whether or not the flap was delayed.     

Differential effects of venous stasis and arterial insufficiency on tissue oxygenation in myocutaneous island flaps: an experimental study in pigs.

The supply, consumption, and tissue tension of oxygen were studied in experimental bilateral myocutaneous island flaps in five control pigs and in eight pigs during progressive 1-hour intervals of flap ischemia. Progressive ischemia was obtained by partial to complete clamping of the artery in one flap, producing arterial insufficiency, and simultaneous clamping of the vein in the other flap, producing venous stasis. Blood flow was reduced to 50, 25, and 0 percent of baseline. In the arterial insufficiency flaps, the oxygen tension in subcutaneous tissue, muscle, and venous outflow was significantly reduced once blood flow was reduced to 50 percent of baseline. Oxygen consumption during partial vessel occlusion was lower in the venous stasis flaps than in the arterial insufficiency flaps when blood flow was reduced to 25 percent of baseline, suggesting either that cellular metabolism is reduced in the venous stasis flaps or that the oxygen which is delivered is unavailable for the cells. Increased presence of tissue fluid in the venous stasis flap inhibits the diffusion of oxygen through the interstitial tissue, and this may explain the lower oxygen consumption. During 3 hours of reperfusion, increased blood flow was observed in the arterial insufficiency flaps, whereas blood flow in the venous stasis flaps was sluggish. The arterial insufficiency flaps recovered more rapidly than the venous stasis flaps during the first hour of reperfusion, judged by the rate of increase in oxygen tension and the higher venous oxygen tension. Oxygen tension increased more rapidly in muscle than in subcutaneous tissue.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of vascular delay on viability, vasculature, and perfusion of muscle flaps in the rabbit

The delay procedure is known to augment pedicled skin or muscle flap survival. In this study, we set out to investigate the effectiveness of vascular delay in two rabbit muscle flap models. In each of the muscle flap models, a delay procedure was carried out on one side of each rabbit (n = 20), and the contralateral muscle was the control. In the latissimus dorsi flap model, two perforators of the posterior intercostal vessels were ligated. In the biceps femoris flap model, a dominant vascular pedicle from the popliteal artery was ligated. After the 7-day delay period, the bilateral latissimus dorsi flaps (based on the thoracodorsal vessels) and the bilateral biceps femoris flaps (based on the sciatic vessels) were elevated. Animals were divided into three groups: part A, assessment of muscle flap viability at 7 days using the tetrazolium dye staining technique (n = 7); part B, assessment of vascular anatomy using lead oxide injection technique (n = 7); and part C, assessment of total and regional capillary blood flow using the radioactive microsphere technique (n = 6). The results in part A show that the average viable area of the latissimus dorsi flap was 96 +/- 0.4 percent (mean +/- SEM) in the delayed group and 84 +/- 0.7 percent (mean +/- SEM) in the control group (p < 0.05, n = 7), and the mean viable area of the biceps femoris flap was 95 +/- 2 percent in the delayed group and 78 +/- 5 percent in the control group (p < 0.05, n = 7). In part B, it was found that the line of necrosis in the latissimus dorsi flap usually appeared at the junction between the second and third vascular territory in the flap. Necrosis of the biceps femoris flap usually occurred in the third territory, and occasionally in both the second and the third territories. In Part C, total capillary blood flow in delayed flaps (both the latissimus dorsi and biceps femoris) was significantly higher than that in the control flaps (p < 0.05). Increased regional capillary blood flow was found in the middle and distal regions, compared with the control (p < 0.05, n = 6). In conclusion, ligation of either the dominant vascular pedicle in the biceps femoris muscle flap or the nondominant pedicle in the latissimus dorsi muscle flap in a delay procedure 1 week before flap elevation improves capillary blood flow and muscle viability. Vascular delay prevents distal flap necrosis in two rabbit muscle flap models.     

Comparison of three different supercharging procedures in a rat skin flap model

A significant clinical problem in reconstructive surgery is partial loss of a pedicled flap. To resolve this problem, various methods of vascular augmentation have been developed; "supercharging" is one of those techniques. A new rat flap model was developed for investigation of the supercharging procedure, and the efficacy of the arterial supercharging method was examined. The purpose of this study was to investigate how an arterial supercharging procedure could generate large flap survival areas with different supercharging positions in rats. On the basis of the vascular anatomical features of rats, a circumferential skin flap from the lower abdomen to the back, measuring 4 x 12 cm, was marked. The flap was divided along the dorsal midline. Forty rats were divided into four experimental groups, as follows: group 1 (control), flaps based only on the deep circumflex iliac artery and vein; group 2, flaps supercharged with the ipsilateral superficial inferior epigastric artery; group 3, flaps supercharged with the contralateral superficial inferior epigastric artery; group 4, flaps supercharged with the contralateral deep circumflex iliac artery. On the fourth postoperative day, the flaps were evaluated with measurements of necrosis and survival areas. Microfil (Flow Tech, Inc., Carver, Mass.) was then injected manually throughout the body, and the vascular changes produced by supercharging were angiographically evaluated. Compared with group 1 (control), the flap survival areas were significantly greater in distally supercharged flaps in groups 3 and 4 (mean flap survival, 91.2 +/- 5.2 percent and 90.5 +/- 10.6 percent, respectively; p < 0.001) and in proximally supercharged flaps in group 2 (45.9 +/- 4.1 percent, p < 0.05). Angiographic assessment of the flaps that survived completely revealed marked dilation of the choke veins among the territories and reorientation of dilated veins along the axes of the flaps. This study suggests that distal arterial supercharging (contralateral superficial inferior epigastric artery or contralateral deep circumflex iliac artery) is more effective than proximal arterial supercharging (ipsilateral superficial inferior epigastric artery) in increasing flap survival. Although the rat skin flap may not be analogous to human flaps, distal arterial supercharging might have useful therapeutic potential in increasing flap survival in clinical practice.     

Effect of hyperbaric oxygen and medicinal leeching on survival of axial skin flaps subjected to total venous occlusion

This study evaluates the effect of hyperbaric oxygen and medicinal leeching on axial skin flaps subjected to total venous occlusion. Axial epigastric skin flaps (3 x 6 cm) were elevated on their vascular pedicles in 40 male Wistar rats. Total venous occlusion was achieved by division of all veins draining the skin flap. Arterial inflow was left intact. Animals were randomly assigned to one of five groups: sham (n = 8); control, total venous occlusion only (n = 8); occlusion with hyperbaric oxygen (n = 8); occlusion with leeching (n = 8); occlusion with leeching and hyperbaric oxygen (n = 8). The hyperbaric oxygen protocol consisted of 90-minute treatments, twice daily, with 100% O2 at 2.5 atmospheres absolute for 4 days. The leeching protocol consisted of placing medicinal leeches on the congested flaps for 15 minutes, once daily, for 4 days. Laser Doppler measurements of flap perfusion were recorded preoperatively, postoperatively, and on postoperative days 1 and 3. The percentage of flap necrosis was evaluated on postoperative day 3. Mean percentage necrosis and mean laser Doppler readings were compared between both groups. The flaps in the sham group demonstrated 99 percent survival, whereas the flaps in the occlusion-only group demonstrated 100 percent necrosis. The flaps in the occlusion with oxygen, the occlusion with leeching, and the occlusion with oxygen and leeching groups demonstrated 1, 25, and 67 percent survival, respectively. Sham laser Doppler readings remained within normal limits. Laser Doppler readings in the occlusion-only and the occlusion with oxygen groups decreased to negligible levels on postoperative day 1, and on postoperative day 3 no perfusion was demonstrated. In both the occlusion with leeching and the occlusion with leeching and oxygen groups, there was also a significant decrease in laser Doppler measurements after surgery, but perfusion remained stable throughout the remainder of the study. This study demonstrates that hyperbaric oxygen alone is not an effective treatment for skin flaps compromised by total venous occlusion. The combination of leeching and hyperbaric oxygen treatment of total venous occlusion results in a significant increase in flap survival above that found with leeching alone. It appears that hyperbaric oxygen is effective because of the venous outflow provided by leeching as demonstrated by laser Doppler flow readings.     

The prepuce free flap in 10 patients: modifications in flap design and surgical technique

The prepuce free flap was used in 10 oral and oropharyngeal reconstructions. During the course of this study, various modifications took place. Residual penile skin necrosis and skin island necrosis early in the series led to modification of flap design. This solved the donor-site problem by placing the skin island more proximally, to consist of the outer layer of the prepuce and an equidimensional area of penile skin proximal to the prepuce. Identification of the vascular pedicle was greatly facilitated by changing to retrograde dissection, making skin incision in the mons veneris superfluous. Incongruence between donor and recipient artery, together with microsurgical arrogance, resulted in (resolvable) inflow problems in four patients. One flap was lost. After modification, marginal necrosis still occurred in one flap, most likely because of an episode of venous congestion. Although much care was taken to not harvest more skin than in a regular circumcision, penile skin shortage, especially during erection, appeared to be the major long-term shortcoming of this flap. Flap thinness and pliability, both expected strongholds of the flap, were evident during flap inset, but less apparent during follow-up because of postoperative radiotherapy in the majority of the cases. The best indications for this flap include defects in the tonsillar area extending into the soft palate, tongue, lateral oropharynx, retromolar trigonum, gums, and vallecula.     

The trauma of suction-assisted lipectomy cannula on flap circulation in rats.

The effect of suction-assisted lipectomy on cutaneous blood vessels of inguinal skin flaps was studied and compared in 191 rats. Different types of cannula tips were used; the number of passes was standardized. In one experiment, following suctioning, 3 X 2 cm groin island flaps based on inferior epigastric pedicles were raised and then reattached. Fluorescein dye study and microangiography were performed to evaluate flap viability. Flap survival was determined clinically and by histologic examination on the fifth postoperative day. Three-sided inguinal random-pattern flaps were raised in a second experiment and reattached following suctioning. On the fifth postoperative day, surviving flap areas were measured using standard photographs and an imaging computer and were compared with controls. Results showed that cannula passes accompanied by vacuum are harmful to vessels, while those unaccompanied by vacuum are not. The greater the number of suctioning passes, the more trauma there is to vessels and the greater is the likelihood of flap necrosis. Conical and spatula tips were more harmful to vessels than spherical, cobra, keel cobra, or Fournier tips. These results support the conclusion that suction-assisted lipectomy enhances the possibility of skin necrosis by traumatizing the vascular pedicle of a flap, especially when it is used as an adjunct to flap elevation.     

Myocutaneous flap ischemia: flow dynamics following venous and arterial obstruction.

To further clarify the pathogenesis of the poorer prognosis in skin flaps exposed to venous stasis compared with arterial insufficiency, a microsphere study was conducted in bilateral rectus abdominis island flaps in seven pigs. The relationship between capillary blood flow and arteriovenous (A-V) shunting was studied during progressive 1-hour intervals of arterial insufficiency and venous stasis and during 3 hours of reperfusion. Under controlled conditions, total blood flow was reduced from 100 percent to both 50 and 25 percent by application of an adjustable clamp on the artery supplying one flap and on the vein draining the contralateral flap. The relative distribution between A-V shunt flow and capillary blood flow was different in arterial insufficiency when compared with venous stasis at both the 50 percent and the 25 percent blood flow levels. In the arterial insufficiency flaps, the A-V shunt flow and capillary blood flow shared the total blood flow in the following percentages: 64/36 (at 100 percent total blood flow), 44/56 (at 50 percent total blood flow level), and 22/78 (at 25 percent total blood flow level). In the venous stasis flaps, the A-V shunt flow and the capillary blood flow shared the total blood flow in percentages of 70/30, 66/34, and 55/45, respectively. Hence, in arterial insufficiency flaps, capillary blood flow was spared by a relatively greater decline in A-V shunting compared with venous stasis flaps. Redistribution of capillary blood flow from subcutaneous tissue to muscle was observed, whereas blood flow was equally distributed throughout the length of the flaps at all flow levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

A new island flap transfer from the dorsum of the index to the thumb.

We describe here a new island flap from the dorsum of the index finger, transferred on the first dorsal metacarpal artery with one or two veins and the terminal branches of the radial nerve. This vascular bundle is a reliable one, for we have had no necrosis in 12 consecutive cases. The quality of its venous outflow and the use of a dorsal donor site give it advantages over the Moberg-Littler island flap, unless a dorsal vein from the latter flap is preserved and sutured to a vein in the recipient site. The arterial vascularization without any skin pedicle makes this "kite" flap a more practical one than the "flag" flaps of Vilain or Holevitch or Kuhn. Finally, a one-stage transfer is usually preferable to a two-stage one (e.g. Adamson, Braillar). In a single operation, this transfer provides composite resurfacing of the thumb while bringing in new blood and nerve supply.     

Local pharmacological preconditioning increases the survival of experimental skin flaps in rats

Skin flap survival is dependent on an adequate blood supply and on the resistance to ischemia. Experimentally we tested the effect of pharmacological preconditioning on the survival of skin flaps. The survival of an ischemic skin flap (McFarlane flap) was tested using the local application of cobalt gel in three groups of Wistar rats. The mean flap necrosis of the control group was 59.15%. The rats treated by the cobalt gel once a week showed mean necrosis in 39.09%; the rats receiving the application of the cobalt gel three times a week in 26.33%. The treated groups presented with significantly lower flap necrosis in comparison to the untreated controls. There was a significant difference in the flap necrosis occurrence according to the application frequency of the cobalt gel. The expression of the genes involved in angiogenetic processes encoding vascular endothelial growth factor (VEGF) and glycolytic enzymes was influenced in a non-mitochondrial way in this study. The results show that non-mitochondrial preconditioning could prolong the survival of an ischemic flap.     

The effects of a topical PGE2 analogue on global flap ischemia in rats

The present study evaluated the ability of DHV-PGE2ME, a topically effective 16-vinyl prostaglandin E2 analogue, to improve the tolerance of skin flaps to a period of ischemia. DHV-PGE2ME and placebo were applied to bilateral island flaps on 70 anesthetized rats; then the vascular pedicle of each flap was clamped for 10 hours. Treated flaps evidenced significantly better reperfusion, as documented by quantification of fluorescein dye delivery at 90 minutes after clamp release, and they had significantly greater ultimate viability (p less than 0.05, by ANOVA). While less than 3 percent of untreated flaps survived, those treated with 1.75 and 17.5 microgram/cm2 of drug evidenced 76 and 86 percent survival, respectively. Treatment of a given flap did not affect its contralateral mate, since there was no evidence of a systemic effect. Especially since its effect can be limited to the site of application, DHV-PGE2ME should be valuable for the treatment of compromised perfusion in a variety of settings.     

The optimal sequence of microvascular repair during prolonged clamping in free flap transfer

During free flap transfer, the surgeon may decide to begin with repair of the artery or the vein(s) and to unclamp the first vessel as soon as repair is completed or maintain the clamping of both vessels until completion of all repairs. Complications can lead to prolonged clamping times, potentially increasing the risk of tissue ischemia, vascular damage, and thrombosis. The goals of the present study were to determine whether the sequence of vessel repair and the duration of clamping affect the success of free flap transfer in cases requiring prolonged clamping. Sixty abdominal fasciocutaneous free flaps based on the superficial inferior epigastric vessels were created in Sprague-Dawley rats. To model clinical situations in which prolonged clamping is necessary, the study used a 1-hour delay before the repair of the second vessel. Flaps were randomized into four groups. In group I (n = 15), the artery was repaired first, and the arterial clamp was removed immediately to allow arterial inflow. In group II (n = 15), the arterial repair was first, and the arterial clamp was maintained until completion of venous repair. In group III (n = 15), venous repair was first, with venous clamping maintained until completion of the arterial repair. In group IV (n = 15), initial venous repair was followed by immediate unclamping, before arterial repair. On release of all clamps, the patency of arteries and veins was confirmed immediately and after 1 hour using a "milking" test. On the fifth postoperative day, each flap was assessed for necrosis and for patency of the anastomoses. Of 15 flaps in each group, five (33 percent) failed in group I, four (27 percent) failed in groups II and III, and six (40 percent) failed in group IV. Differences between groups were not statistically significant (p = 0.8). These results demonstrate that in cases requiring prolonged occlusive clamping (2 to 3 hours), factors such as venous congestion, possible clamp injury, and presence of static blood in contact with the new anastomosis have relatively equivalent contributions to the risk of failure. Accordingly, no advantage seems to be gained by beginning with the artery or the vein or by using early or delayed unclamping of the first vessel repaired.