The effects of the perfusion of various solutions on the no-reflow phenomenon in experimental free flaps.

The effects of solution perfusion in the free epigastric flap of the rabbit, after normothermic ischemic periods of 8 hours or 12 hours, have been examined by operative microscopic and histological methods. A smaller group of animals was also studied in which the perfusion was done before the ischemic insult. An ischemia-related obstruction to the peripheral blood flow occurred in the absence of stagnant ischemic blood in this model. Although the 3 perfusion fluids studied were shown to penetrate to all levels of a flap after such an ischemic period, none of them had a beneficial effect on skin survival. However, the solution containing mannitol did have a protective effect on fat survival. Analogies between these experimental findings and the clinical situation are made, and the importance of the early diagnosis and treatment of ischemia in a flap is emphasized.     

Beneficial effects of ibuprofen on experimental microvascular free flaps: pharmacologic alteration of the no-reflow phenomenon

Pharmacologic alteration of the no-reflow phenomenon was determined based on increased tolerance to ischemia in ibuprofen-treated free flaps. Sprague-Dawley rats (N = 60) were divided into control (lactated Ringer's) and treated (ibuprofen) groups and subdivided into six groups of ischemia: 1 hour, 6 hours, 8 hours, 10 hours, 12 hours, and 14 hours of ischemia. Fluorescein uptake was measured after 10, 30, and 60 minutes following microrevascularization. Dye elimination studies were done for each ischemia group that demonstrated good fluorescein uptake. All free flaps in the 1-, 6-, and 8-hour groups survived. The ibuprofen-treated 10- and 12-hour flaps all survived, whereas the 10-hour control and 14-hour ibuprofen-treated free flaps failed to survive. Despite high fluorescein uptake, the 14-hour ibuprofen-treated flaps did not eliminate the fluorescein, whereas all surviving free flaps adequately eliminated the fluorescein. Failure to eliminate dye despite adequate uptake suggested a deranged microcirculation with increasing ischemia time. By inhibiting cyclo-oxygenase, nonsteroidal anti-inflammatory agents such as ibuprofen may block the untoward effects mediated by thromboxane A2, such as vasoconstriction, microvasculature thrombus formation, and intravascular sludging. These effects are theorized in part to be responsible for the failure of a free flap to survive despite revascularization.     

Evaluation of anastomotic techniques in the experimental transfer of free skin flaps.

Vascularized groin flaps were transferred to the contralateral side by various microvascular anastomotic techniques. There was no statistical difference between the results of end-to-end and end-to-side anastomoses, when the same sized vessels were compared. However, significant differences existed when vessels smaller than 0.5 mm in diameter were anastomosed.     

Free-style free flaps

Free-tissue transfer has become the accepted standard for reconstruction of complex defects. With the growth of this field, anatomic studies and clinical work have added many flaps to the armamentarium of the microvascular surgeon. Further advancements and experience with techniques of perforator flap surgery have allowed for the harvest of flaps in a free-style manner, where a flap is harvested based only on the preoperative knowledge of Doppler signals present in a specific region. Between June of 2002 and September of 2003, 13 free-style free flaps were harvested from the region of the thigh. All patients presented with an oral or pharyngeal cancer and underwent resection and immediate reconstruction of these flaps. All flaps were cutaneous and were harvested in a suprafascial plane. The average size of the flaps was 108 cm2 (range, 36 to 187 cm2), and the average length of the vascular pedicle was 10 cm (range, 9 to 12 cm). All flaps were successful in achieving wound coverage and functional outcomes without any vascular compromise necessitating re-exploration. Free-style free flaps have become a clinical reality. The concepts and techniques used to harvest a free-style free flap will aid in dealing with anatomic variations that are encountered during conventional flap harvest. Future trends in flap selection will focus mainly on choosing tissue with appropriate texture, thickness, and pliability to match requirements at the recipient site while minimizing donor-site morbidity.     

The use of free groin flaps in children

The free groin flap is a well-established method of skin coverage. Although its use in children has been reported, there have been no published series specifically in such cases. The authors report 33 consecutive cases of free groin flaps in children in their unit over a period of 9 years (1992 to 2001). Tissue transfer was performed to provide soft-tissue coverage during reconstruction of congenital defects and tumor resection and following trauma. Twenty-six cases (79 percent) involved the upper limb, six cases (18 percent) involved the lower limb, and one case involved the head. The complication rate compares favorably with similar series published for adults, with only two complete failures (6 percent), three (9 percent) minor donor-site complications (superficial wound infection, hypertrophic scarring, and dog-ears), and nine flaps requiring debulking. The reexploration rate was 24 percent, with seven of the eight flaps undergoing reexploration surviving. The groin flap is a reliable flap that can be used safely in children, with minimal morbidity.     

Ischemic injury to enteric free flaps: an experimental study in the dog

Enteric free flaps have proven to be useful for reconstructing the cervical esophagus. Although jejunum is favored, the rationale for this is not at all clear. We have postulated that resistance to warm ischemia varies in different regions of the gut. An experiment was carried out in 10 mongrel dogs in which 10-cm segments of proximal, middle, and distal small bowel were isolated on single vascular pedicles. In each portion of the gut there were three segments: a control, a segment subjected to 60 minutes of warm ischemia, and a segment subjected to 120 minutes of warm ischemia. The following day each animal was reexplored, and the viability of bowel segments was assessed visually and with fluorescein. All control segments were viable at 24 hours. Twenty segments were subjected to 1 hour of warm ischemia, and all but two were viable. Nineteen gut segments were subjected to 2 hours of warm ischemia. Seven of eight proximal segments were viable, two of five midsegments were viable, and zero of six distal segments were viable. Survival in the distal portion compared to the proximal portion was significantly less (p less than 0.01). It appears from this study that isolated distal small bowel segments are less resistant to warm ischemia than proximal segments.     

The timing and nature of neovascularization of jejunal free flaps: an experimental study in a large animal model.

The present study was designed (1) to determine whether a free jejunal transfer in a large animal model can develop collateral circulation that is adequate to maintain viability after division of the pedicle and (2) to determine the earliest time pedicle ligation is safe after transplantation. A 15-cm jejunal segment was transferred to the necks of 18 dogs weighing 25 to 35 kg. The bowel segment was inset longitudinally under the skin on one side of the neck, partially covered by the neck muscles, and the mesenteric vessels were anastomosed to recipient vessels in the neck. The proximal and distal bowel stomas were exteriorized through skin openings 12 cm apart and matured. The dogs were subjected to ligation of the vascular pedicle at different intervals: postoperative day 7 (group I, n = 3), day 14 (group II, n = 5), day 21 (group III, n = 5), and day 28 (group IV, n = 5). Blood perfusion was measured in the proximal and distal bowel stomas before pedicle division (control) and 24 hours later using hydrogen gas clearance and fluorescein dye. Bowel necrosis was analyzed using planimetry. The bowel was also stained with hematoxylin and eosin and factor VIII, and new blood vessels were counted. Mean values (+/- standard deviation) were compared with control values for each test and with normal values in the intact bowel using analysis of variance with Neumann-Keuls post-hoc test for multiple comparisons. No jejunal free flaps survived when the vascular pedicle was divided 1 week postoperatively. Bowel survival was 60 percent at 2 weeks, 83 percent at 3 weeks, and 100 percent at 4 weeks. Hydrogen gas clearance values (ml/min/100 g) were 49.6 +/- 8.7 in the mucosa of the intraabdominal jejunum and 37.9 +/- 9.4 in the jejunum that was transferred to the neck before division of the pedicle. Twenty-four hours after pedicle division, hydrogen gas clearance values were 2.8 +/- 6.4 in group I (p < 0.05), 22.4 +/- 12.4 in group II, 23.9 +/- 9.3 in group III, and 34.2 +/- 7.5 in group IV. FluoroScan readings in the transferred jejunum were 201 +/- 7.2 in the control group, 9.3 +/- 2.8 in group I (p < 0.05), 79.1 +/- 10.6 in group II, 66.2 +/- 7.3 in group III, and 164 +/- 11.9 in group IV. New vessel formation as identified by factor VIII staining correlated with increasing bowel perfusion and flap survival rate. Bowel neovascularization, perfusion, and survival increased progressively 1 week after transfer. Significant portions of the transferred bowel will neovascularize and survive as early as 2 weeks postoperatively. However, a minimum of 4 weeks before ligation of the pedicle is necessary to maximize flap perfusion and guarantee survival.     

Capillary plugging by granulocytes and the no-reflow phenomenon in the microcirculation

Granulocytes are large, stiff viscoelastic cells that adhere naturally to the vascular endothelium. On their passage through the capillary network they have to be deformed, and recent evidence indicates that they may impose a significant hemodynamic resistance. The entry time of granulocytes into capillaries is about three orders of magnitude longer than that for red cells. Inside the capillary the granulocytes move with a lower velocity than red cells. Under conditions when the capillary perfusion pressure is reduced and/or elevated levels of inflammatory products are present that increase the adhesion stress to the endothelium, granulocytes may become stuck in the capillary. In such a situation, the granulocytes form a large contact area with the capillary endothelium, they obstruct the lumen, and they may initiate tissue injury. After the restoration of the perfusion pressure the granulocytes may not be removed from the capillary owing to the adhesion to the endothelium. Capillary plugging by granulocytes appears to be the mechanism responsible for the no-reflow phenomenon, and together with oxygen free radical formation and lysosomal enzyme activity may constitute the origin for ischemic injury as well as other microvascular occlusive diseases.     

Study of the delay phenomenon in axial pattern flaps in pigs.

A technique, using radioactively-tagged microspheres to measure the blood flow in delayed axial pattern flaps in the pig, is presented. The blood flow was significantly (p less than 0.01) increased in the delayed portion of these flaps, reaching maximal levels after 4 to 12 days of delay. Also, the blood flow to these flaps correlated with tissue survival during the first week after the delay (p less than 0.001).     

Preischemic flap washout and its effect on the no-reflow phenomenon

Preischemic perfusion washout with an acellular physiologic solution delays the no-reflow phenomenon and improves tissue survival in rat epigastric free flaps following 18 and 24 hours of normothermic ischemia. This implies that stagnating blood may be a causative agent in the no-reflow phenomenon. A possible mechanism for this is capillary endothelial damage secondary to the presence of formed blood cells or their products of hemolysis. Perfusion washout may improve ischemic tolerance by preventing this blood cell-induced endothelial damage and by the prevention of sludge and thrombus. Whether any of the metabolic components of the perfusate actively enhance ischemic tolerance cannot be definitively stated.     

Experience with thirteen latissimus dorsi myocutaneous free flaps.

Subcutaneous "pocketing" is proposed as a simple and convenient method to nourish a denuded, replanted end of a finger, when the amputation is between the lunule and the DIP joint. The investigation of a laboratory model is presented, and our initial clinical experience is reported.     

Regional intravascular sympathetic blockade for better results in flap surgery: an experimental study of free flaps, island flaps, and pedicle flaps in the rabbit ear

Flap survival is still a major problem in reconstructive surgery. Increased flap survival after systemic administration of drugs inhibiting the adrenergic system has been reported in experimental studies. The clinical use, however, is restricted by systemic side effects. It has been demonstrated that, using guanethidine, an effective regional intravascular sympathetic (RIS) block can be obtained without systemic effects. Using this type of block, an experimental study was made on the survival and quality of different types of flaps in the rabbit ear. The results obtained in 72 flaps created in the ears of 36 rabbits were assessed by the extent of flap edema, peripheral neovascularization, flap temperature, and flap surviving area. The RIS block reduced edema and scab formation, caused higher flap temperatures, better neovascularization, and increased surviving flap area, as compared with equal flaps in the untreated contralateral ear of the same animal. The effect of RIS block may be considered as a "pharmacological delay" procedure. From the experiments as well as clinical experience, it may be concluded that this technique is a safe and effective procedure. Therefore, the RIS block method is recommended for clinical use in flap techniques in extremities of man.     

Sensibility and cutaneous reinnervation in free flaps

Sensibility and sensory reinnervation were investigated in 19 free flaps, predominantly located on the lower extremities, between 2 months and 3 years after flap transfer. All patients showed deep pressure sensibility. In 10 of the patients, primarily those examined late after surgery, a heat pain threshold was obtained at about 50 degrees C. None of the patients had superficial sensibility of any other modality. No neurofilament-positive sensory nerve fibers were observed in the dermis or epidermis. In one patient nerve fibers were detected in the subcutaneous tissue. It is concluded that patients will have deep pressure sensibility of the flap area even early after the operation and that most patients will develop a heat pain sensitivity, probably due to subcutaneous reinnervation.