Blood Flow In Flaps Research Articles

Measurement of Flap Blood Flow by Laser Doppler Velocimeter in Oral Surgery

Recently the laser doppler velocimeter has been developped as aids in evaluation of microcircuratory flow in a variety of human tissue. We have used this instrument to measure viability of the flaps which were transplanted to the reconstruction of maxillo-facial region.The blood circulation of D-P flaps and Abbe flap were measured by laser doppler verocimeter. The analog data of the blood circulation was analyzed by using personal computer. The software for data analysis was developped by ourselves.The laser doppler verocimeter is a non-invasive instrument capable of instantaneous and continuous evalation of local flow in tissue microcirculation. It is fit to monitor viability of flaps used oral and maxillo-facial surgery.

A Study of the Relationship Between Blood Flow and Bacterial Inoculation in Musculocutaneous and Fasciocutaneous Flaps

Regional nutrient blood flow to musculocutaneous and fasciocutaneous flaps was studied in dogs using 15-microns radiolabeled microspheres, and correlations to bacterial inoculation into closed wound spaces were sought. During the 6-day study period, no differences were found between blood flow to noinoculated versus inoculated flaps. Comparisons of blood flow to the deep surfaces of the flaps showed that blood flow to muscle in musculocutaneous flaps increased rapidly during the first 24 hours and then plateaued, while that to subcutaneous tissue plus fascia in fasciocutaneous flaps demonstrated a gradual and steady increase. The most rapid decline in bacterial counts at the undersurface of both flaps occurred within 24 hours, dropping significantly lower within musculocutaneous flaps. In addition to such surface properties of muscle as tissue ingrowth, rapid early augmentation of muscle blood flow may be largely responsible for superior bacterial suppression observed beneath musculocutaneous flaps.

A Study of the Relationship Between Blood Flow and Bacterial Inoculation in Musculocutaneous and Fasciocutaneous Flaps

Gosain, Arun M.D.; Chang, Ning M.D.; Mathes, Stephen M.D.; Hunt, Thomas K. M.D.; Vasconez, Luis M.D.; Antoine, Gregory A. M.D.; Van Beek, Allen L. M.D. Author Information

The Influence of Tissue Tension on the Microcirculation in Myocutaneous Flaps: An Experimental Study in Dogs

The effect of increased and decreased uniaxial tissue tension on capillary blood flow, plasma volume, edema formation, and vascular permeability in myocutaneous flaps was studied. A total of 64 equally sized arterialized myocutaneous flaps were outlined on the abdomen of 16 dogs. The four areas on each dog were randomized to either untouched control area, reattachment to normal tension, increased (one and one-half times the original length), or decreased (one-half times the original length). Capillary blood flow measured by the radioactive microsphere technique two hours after operation was decreased in the muscular part of flaps reattached at decreased and normal tension (p less than 0.05). The muscular blood flow was unchanged when flaps were reattached at increased tension and significantly higher than in flaps reattached at decreased tension (p less than 0.05). No differences were found in skin or subcutaneous blood flow. There were no differences in plasma volume, vascular permeability, or total water content between flaps attached under different tensions, whereas the plasma volume was increased in muscle in all three flap types (p less than 0.05) presumably secondary to venous stasis. The study implies that the decreased capillary blood flow seen in the muscular component of a myocutaneous flap in the immediate postoperative period may be counteracted by a somewhat increased reattachment tension.

A Study on the Effectiveness of a Thromboxane Synthetase Inhibitor (OKY-046) in Increasing the Survival Length of Skin Flaps

In an experimental study to test the thromboxane (TX) synthetase inhibitor OKY-046, two random-pattern skin flaps, each measuring 15.5 x 2 cm, and caudally based, were elevated on the backs of rabbits, and the effect of the test drug on their survival length was evaluated. The results indicated that the survival length of the skin flaps was 4.5 +/- 0.2 cm in the control group and 6.8 +/- 0.3 cm in the OKY-046-treated group, hence exceeding the control value by more than 50 percent, which was statistically significant. A laser speckle flow-meter showed that the OKY-046-treated flaps had significantly greater blood flow as compared with the control group both at 1 and 48 hours after operation. Whereas the blood flow values were significantly lower at 48 hours than at 1 hour after operation in the control group, no such reduction was noted in the OKY-046-treated group. On the other hand, while plasma TXB2 was found elevated at 1 hour postoperatively in the control group, such a response to the surgical intervention was blocked and the plasma TXB2/6-keto prostaglandin (PG) F1a ratio was decreased in the OKY-046-treated group. These results clearly indicated that OKY-046 suppressed a plasma thromboxane elevation induced by surgery, it augmented the flap blood flow, and it thereby increased flap survival length, suggesting that the drug might be helpful clinically and that further investigation must be carried out concerning its application.

Dynamic properties of blood flow and leukocyte mobilization in infected flaps

Two aspects of the inflammatory response to infection--blood flow alteration and leukocyte mobilization--are investigated in the canine model. The elevation of paired musculocutaneous (MC) and random pattern (RP) flaps allowed comparison of healing flaps with significant differences in blood flow (lower in random pattern flaps) and resistance to infection (greater in musculocutaneous flaps). Blood flow changes as determined by radioactive xenon washout were compared in normal skin and distal flap skin both after elevation and following bacterial inoculation. Simultaneous use of In-111 labeled leukocytes allowed determination of leukocyte mobilization and subsequent localization in response to flap infection. Blood flow significantly improved in the musculocutaneous flap in response to infection. Although total leukocyte mobilization in the random pattern flap was greater, the leukocytes in the musculocutaneous flap were localized around the site of bacterial inoculation within the dermis. Differences in the dynamic blood flow and leukocyte mobilization may, in part, explain the greater reliability of musculocutaneous flaps when transposed in the presence of infection.

Surgical Augmentation of Skin Blood Flow and Viability in a Pig Musculocutaneous Flap Model

A porcine rectus abdominis musculocutaneous (TRAM) flap model was designed and validated in nine pigs. This TRAM flap was based on the deep inferior epigastric (DIE) vessels with an 8 x 18 cm transverse skin paddle at the superior end of the rectus abdominis muscle. The model was subsequently used to test our hypothesis of surgical augmentation of flap viability by vascular territory expansion. Specifically, we observed that ligation of the superior epigastric (SE) vessels at 4, 7, 14, and 28 days (N = 6 to 8) prior to raising the TRAM flaps significantly increased (p less than 0.05) the length and area of the viable skin in the transverse skin paddles of the treatment flaps compared with the contralateral shammanipulated control flaps. This significant increase in skin viability was seen to be accompanied by a significant increase (p less than 0.05) in skin and muscle capillary blood flow in the treatment TRAM flaps compared with the controls (N = 9). The mechanism of vascular territory expansion is unclear. We postulate that hypoxia resulting from the ligation of the superior epigastric vessels prior to the flap surgery may play a role in the triggering of the deep inferior epigastric artery to take over some of the territory previously perfused by the superior epigastric artery. This would then increase the skin and muscle capillary blood flow in the transverse paddle when the TRAM flap was raised on the deep inferior epigastric vascular pedicle.

Regional Variations of Laser Doppler Blood Flow in Ischemic Skin Flaps

An island skin flap was designed on the left inferior epigastric neurovascular bundle of anesthetized male rats. Blood flow was measured in situ with a laser Doppler flowmeter at 20 discrete points on a grid system (5 points in each quadrant of the flap) before and after surgery, or before vascular occlusion, during reperfusion, and 48 to 72 hours later. Two series of experiments were performed. In the first series, the raised flap was placed in a bath containing heated Ringer's solution and the left pedicle was cross-clamped. After 30 minutes, adenosine at a concentration that produced supramaximal vasodilatation, or its vehicle, was added to the bath. After 1 hour total occlusion time, the vascular clamp was released and adenosine treatment was continued for the first 30 minutes of reperfusion. In the second series, the protocol was similar except that adenosine, or its vehicle, was infused into the ischemic flap by means of the distal stump of the right inferior epigastric artery. After 48 to 72 hours, fluorescein was injected IV. The data showed a significant regional variation in baseline laser Doppler blood flow that was further altered by surgically raising the flap. Whereas proximal axial laser Doppler blood flow was essentially unchanged from the preoperative baseline, distal axial laser Doppler blood flow decreased 10 to 50 percent, and proximal and distal dependent laser Doppler blood flow decreased 50 to 80 percent. Thus no single value accurately reflected total flap perfusion. Necrosis occurred only in the dependent flap regions, which confirmed previous work. In the dependent regions, especially along the incision line, postoperative laser Doppler blood flow was lowest.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of Electrical Nerve Stimulation (ENS) In Ischemic Tissue

Blood flow was measured in the skin flaps of 20 patients who had undergone reconstructive surgery. All flaps were showing clinical signs of deficient circulation. Local blood flow in skin flaps was significantly increased by electrical nerve stimulation (ENS) (p less than 0.001), but not by placebo ENS. Repeated ENS treatment reduced stasis and oedema significantly (p less than 0.001), and the capillary refill was also significantly improved (p less than 0.001).

Ischaemia reperfusion injury in pedicle skin flaps in the pig: lack of protective effect of SOD and allopurinol

A model of ischaemia and reperfusion was established which consistently achieved a 50% reduction in viable length of random pattern pedicle skin flaps in pigs. Flaps were subjected to two periods of ischaemia and reperfusion. Superoxide dismutase (SOD) in a dose of 3000 u/kg given intravenously and allopurinol 70 mg/kg/day orally had no effect on viable skin flap length, skin blood flow or histological characteristics of flaps. SOD polymers, which have been used in other species to delay SOD clearance, were found to cause anaphylactoid reactions in pigs.

Early Circulatory and Metabolic Events in Island Skin Flaps of the Pig

Circulatory and metabolic skin-flap events were studied prior to and up to 6 hours after elevation of buttock island flaps in pigs. During the elevation, significant reductions in superficial skin blood flow, measured by laser Doppler flowmetry (LDF) and dermal flap temperature, were seen. Significant correlations were found between blood flow and temperature. Total flap blood flow, measured as venous outflow, also showed an initial transient decrease, but 2 hours after flap construction, venous outflow had returned to preoperative values. A significant increase in lactate release, together with increased oxygen consumption and glucose uptake, was seen 4 hours after the surgical intervention. Hypoxanthine release, indicating ischemia, was seen only during the first hour after flap elevation. Noradrenaline outflow was noted after 4 and 6 hours, but there was no parallel reduction in flap blood flow. A great deal of the flow reduction in acutely elevated island flaps may thus be due to primary hypothermia rather than to the degenerative release of noradrenaline, which seems to have no early effect on skin flap blood flow. On the other hand, the noradrenaline release may be linked to an increased metabolic activity in the skin flaps.

Circulatory and metabolic events in pig island skin flaps after arterial or venous occlusion.

After 1 hour of arterial or venous occlusion, the circulatory and metabolic events in island skin flaps of the pig were studied. Both occlusion types showed significant but transient increases in glucose uptake and a parallel release of lactate, hypoxanthine, and potassium. Oxygen uptake and noradrenaline release were not significantly affected. No significant difference between the arterial and venous occlusions was seen in the metabolic parameters. The flap blood flow, measured by total venous outflow and laser Doppler flowmetry, was significantly lower after venous than after arterial occlusion. This long-lasting difference in flow response may help to explain the observation that venous occlusion is more deleterious to skin flaps than arterial occlusion. A mechanism underlying these results may be more pronounced microthrombotization and/or edema formation after venous occlusion than after arterial occlusion.

Direct Monitoring of Nutritive Blood Flow in a Failing Skin Flap

A new experimental skin-flap model is presented in which direct observations of blood flow in individual capillaries can be made from the time of flap creation throughout the entire evolution of the establishment of necrosis. After flap creation, one observes through the microscope that at 1 hour a large area of tissue is nonperfused as a result of the surgical trauma. This is followed by vasodilatation at 6 hours, resulting in an increase in the area of perfused tissue. At 24 hours, the vasodilatation persists, and the red cells that have entered the tissue during the vasodilatation (6 hours) accumulate in the capillaries, this being reflected by an increased area of nonperfused tissue. This increase continues to 72 hours, at which time the perfusion-nonperfusion interface becomes well defined and remains so throughout the 5-day experiment. Analyses of the relationship between early postoperative capillary perfusion and eventual necrosis are presented. Advantages and disadvantages of this model are listed.

Dermofluorometry

The dye fluorescence index (DFI) has been cited as an accurate predictor of skin-flap survival. However, two thresholds, one each for flap survival and flap necrosis, have been advocated. A DFI of less than 15 to 20 percent predicts failure, and a DFI greater than 35 to 50 percent predicts survival. Values of 20 to 35 percent indicate an uncertain outcome. The present study was undertaken (1) to determine the optimum threshold for flap survival prediction in pigs, and (2) to compare dermofluorometry with flap blood flow as measured by radioactive microspheres. Dermofluorometry was found to be an accurate (90 percent) and repeatable predictor of skin and fasciocutaneous flap survival in pigs. At 2 and 5 hours after flap elevation, the optimum DFI thresholds are 7 and 27 percent, respectively. This reflects the dynamic nature of circulation in acute skin flaps and the increased dye delivery over time. Using these calculated thresholds, a high degree of correlation was found with survival estimated at 24 hours. Dermofluorometry also was correlated with the blood flow index. Thus not only is it an accurate flap monitor, but a quantitative estimate of flap blood flow can be obtained.

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.

Calcitonin gene-related peptide (CGRP) and transcutaneous electrical nerve stimulation (TENS) increase cutaneous blood flow in a musculocutaneous flap in the rat.

The effect of blood flow on transcutaneous electrical nerve stimulation (TENS) and injection of calcitonin gene-related peptide (CGRP) was studied in a musculocutaneous flap of the rat, using laser Doppler flowmetry. The circulatory border was estimated before and after treatment. It was shown that repeated treatments with TENS gradually increased the blood flow, moving the circulatory border distally more than 100% after three treatments. Injection of NaCl into the dorsal central vein of the flap resulted in no increase in blood flow, whereas CGRP 10(-10) M increased the blood flow, so that the circulatory border moved distally 70% and 60%, respectively.

Effect of ischemic skin flap elevation on tissue and plasma thromboxane A2 and prostacyclin production: modification by thromboxane synthetase inhibition.

The circulating prostaglandins have been implicated as mediators of microcirculatory derangements in skin and skin-muscle flaps. The study described here investigated the roles of thromboxane A2 and prostacyclin, measured as thromboxane B2 (TxB2) and prostaglandin 6-keto-F1a (PGF1a), in ischemic skin flaps, and the effects of thromboxane synthetase inhibition on flap blood flow and survival. A canine ventral island flap model was used to measure the appearance of TxB2 and PGF1a in the central arterial and venous plasma, and in the tissue and venous effluent of acutely raised flaps; with and without pretreatment with the specific thromboxane A2 synthetase inhibitor UK38485. Prostaglandin levels change significantly during flap elevation, and can be modified beneficially by thromboxane A2 synthetase inhibition, causing dramatic increases in flap blood flow and survival, as predicted by intravital dye penetration. The results presented in this article suggest that the manipulation of these compounds may provide a method of producing a pharmacological delay phenomenon and perhaps even allow effective intervention in the failing flap.

Variations in flap blood flow and tissue PO2: a new technique for monitoring flap viability.

An implantable and disposable tissue oxygen tension (PO2) probe, useful as a clinical monitor following free-tissue transfer, is described. Experimentally, using the rabbit epigastric groin flap model, we have found it to be a sensitive indicator of arterial and venous occlusion. Oxygen can be given to verify the integrity of the monitoring technique and check any abnormal reading. Animals administered oxygen will have a rapid increase in tissue PO2 when the pedicle is intact. If compromised by arterial or venous occlusion, the low readings demonstrate no change. The application of this new technique for monitoring free flaps in 12 patients is presented. In 2 patients the tissue PO2 monitor successfully detected early vessel thrombosis, resulting in reexploration of the anastomoses and salvage of the free flaps.

The application of laser doppler velocimetry in the determination of blood flow in axial island flaps as a predictor of viability: C. W. Miller, J. H. Roth, T. Lanthier, London, Ontario, Canada

The application of laser doppler velocimetry in the determination of blood flow in axial island flaps as a predictor of viability: C. W. Miller, J. H. Roth, T. Lanthier, London, Ontario, Canada