The effect of prolonged clamping and vascular stasis on the patency of arterial and venous microanastomoses

Utility of the intraflap perfusion procedure for abdominal free flap in unilateral breast reconstruction

BACKGROUND

Heparin prophylaxis for venous thromboembolism can be used in microsurgery. If vein anastomosis is performed before the artery, heparin irrigation into the artery can be performed locally without systematic effect. This study aimed to introduce this "intraflap perfusion procedure" in autologous breast reconstruction.

METHODS

Among the 220 patients with unilateral breast cancer who had received the free abdominal flap, we retrospectively compared those that had undergone the intraflap perfusion procedure (n = 108) and those who did not (n = 112). A 10 mL injection of heparinized physiological saline solution (100 units/mL) was administered into the deep inferior epigastric artery. Intraflap perfusion was performed before, during, and after vein anastomosis, without the vessel clip of the vein. Artery anastomosis was performed without the use of a vein clamp. Further, vein anastomosis was performed tightly to prevent leakage from the vein anastomosis site during artery anastomosis.

RESULTS

The rates of superficial inferior epigastric vein (SIEV) superdrainage (18.5% vs. 42.0%, P < 0.001), and intraoperative flap congestion (0.9% vs. 8.0%, P = 0.01) were significantly lower in patients undergoing this procedure. There were no significant differences regarding other factors (age, BMI, laterality, comorbidities, and other operative details).

CONCLUSIONS

Intraflap perfusion prevented long-term stasis at the venous anastomosis site and capillary level. It could reduce flap congestion. SIEV superdrainage was performed to manage flap congestion, particularly in patients who did not undergo this procedure. Consequently, it can be inferred that this procedure reduces the rate of superdrainage.

Ex Vivo Machine Thrombolysis Reduces Rethrombosis Rates in Salvaged Thrombosed Myocutaneous Flaps in Swine

BACKGROUND

There is a risk for thrombotic complications (2 to 5 percent) associated with microsurgical reconstruction. Current thrombolytic therapy has a salvage rate between 60 and 70 percent, but it is afflicted by bleeding complications (2 to 6 percent). The use of machine perfusion for delivering thrombolytic agents is a new method that could potentially reduce these complications. In this article, the authors compared flap salvage outcomes comparing machine thrombolysis versus a manual flush with tissue plasminogen activator.

METHODS

Sixteen bilateral flaps (12 × 9 cm) were dissected from eight female Dutch Landrace pigs (70 kg). Thrombosis was induced in free rectus abdominis flaps by clamping the pedicle's veins for 2 hours. Flaps were either thrombolysed with 2 mg tissue plasminogen activator (1 mg/ml) during 2 hours of machine perfusion (perfusion group; n = 8) or injected intraarterially (manual group; n = 8) before replantation. Near-infrared fluorescence angiography was used to confirm thrombus formation and to assess tissue perfusion; muscle biopsy specimens were analyzed for ischemia/reperfusion injury directly after thrombolysis and 15 hours after replantation.

RESULTS

A higher incidence of secondary thrombosis was seen in the manual group compared to the perfusion group ( n = 6 versus n = 0, respectively; p < 0.001), resulting in two complete flap failures. Fifteen hours after replantation, mean fluorescence intensities were 13.0 (95 percent CI, 10.1 to 15.8) and 24.6 (95 percent CI, 22.0 to 27.2) in the perfusion and manual group, respectively ( p < 0.001), and mean muscle injury scores were comparable, measuring 7.5 ± 1.5.

CONCLUSION

Two hours of machine thrombolysis of compromised flaps in a porcine model showed higher salvage rates compared to a manual injection with tissue plasminogen activator and reduced the incidence of secondary thrombosis.

CLINICAL RELEVANCE STATEMENT

Using machine perfusion systems for ex vivo thrombolysis provides the benefits of local treatment of a composite tissue without the risk of systemic complications and may improve salvage rates and reduce the incidence of secondary thrombosis.

Ex Vivo Thrombolysis to Salvage Free Flaps Using Machine Perfusion: A Pilot Study in a Porcine Model

BACKGROUND

 Mechanical evacuation of capillary thrombi in free flaps is difficult, and often requires thrombolytic therapy. Utilizing machine perfusion systems, the possibility rises to salvage free flaps ex vivo by administering high doses of thrombolytic agents. The primary aim of this pilot study in a porcine model is to investigate the feasibility of ex vivo thrombolysis using an extracorporeal perfusion machine.

METHODS

 A model of stasis-induced thrombosis was used in 12 free rectus abdominis flaps harvested from six Dutch Landrace pigs. Compromised flaps were ex vivo perfused with University of Wisconsin preservation solution and treated according to the following study groups: (1) 1 mg of tissue plasminogen activator (t-PA) as additive, (2) 3 mg of t-PA as an additive, and (3) no thrombolytic additive. Microcirculation was assessed using near-infrared fluorescence angiography.

RESULTS

 Pedicled abdominal flaps were created and thrombus formation was successfully induced. Eleven abdominal flaps were perfused using the modified heart-lung machine setup. Near-infrared fluorescence angiography showed delayed or no filling was noted in the control group. In comparison, the flaps which were perfused with 1 mg t-PA or 3 mg t-PA as additive showed increased fluorescence intensity curves.

CONCLUSION

 This pilot study in a porcine model presents a reliable and reproductive stasis-induced thrombosis model in free flaps. By adding t-PA to a custom-made extracorporeal perfusion system, the indocyanine green fluorescence intensity curves increased of all flaps that were perfused with different dosages of t-PA as additives, indicating restoration of capillary pressure and microcirculatory inflow.

Outcome of simultaneous and staged microvascular free tissue transfer connected to arteriovenous loops in areas lacking recipient vessels

BACKGROUND

Arteriovenous loops are an indispensable tool in free flap surgery when appropriate recipient vessels are missing. In this study, the authors analyzed whether the outcome differs when flaps were transferred simultaneously or subsequently after construction of arteriovenous loops.

METHODS

Twenty-seven patients requiring free tissue transfer received arteriovenous loops by pedicled or free vein grafts because of inadequate local recipient vessels. In head and neck reconstruction, pedicled brachiocephalic or free saphenous vein grafts were anastomosed to cervical or axillary vessels. Pedicled major saphenous vein grafts were used in the pelvic area whereas, in lower leg and foot reconstruction, free saphenous or brachiocephalic veins were used. Flaps were transferred simultaneously (n = 10) or 4 to 17 days later (n = 17).

RESULTS

Thrombosis required revision in staged transfer (n = 3 patients) or in simultaneous flap transfer (n = 2). No free flap was lost. Fisher's exact test did not indicate a significant difference between a simultaneous or staged flap transfer.

CONCLUSIONS

Temporary arteriovenous loops provide adequate recipient vessels and flow to supply microvascular free flap tissue transfer in areas lacking recipient vessels and in which no other reconstructive options exists. No statistical differences in complications and overall outcome were found between immediate or secondary free tissue transfer. Meticulous monitoring of microvascular perfusion, however, is mandatory in both approaches and early intervention is necessary to ensure successful tissue transfer.

The comparative effects of total hepatic vascular isolation techniques performed at different durations in rat

BACKGROUND

Total hepatic vascular exclusion (THVE) leads to massive venous congestion below the level of diaphragm and may promote undesirable hemodynamic disturbances in some patients. Supraceliac aortic clamping during THVE may achieve hemodynamic stability at the price of arterial ischemia. However, the parenchymal injury of venous congestion has been a greater concern than of arterial ischemia in various settings. We hypothesized that supraceliac aortic occlusion during THVE may attenuate the reperfusion injury and improve the outcome that would be acquired after THVE alone.

MATERIAL AND METHODS

Rats were randomly assigned to (1) THVE alone, (2) THVE plus aortic occlusion, (3) THVE plus celio-mesenteric arterial occlusion or (4) sham during 30, 45, or 60 min followed by 180 min reperfusion period. Serum enzymes (alanine aminotransferase, lactate dehydrogenase) and creatinine as well as tissue "thiobarbituric acid reactive substances" (TBARS) and histopathology were evaluated. Seven animals per group were followed for survival up to 7 d.

RESULTS

After 30 min, no difference was found in serum enzyme, creatinine and tissue TBARS measures among the isolation methods used. In these, all rats survived to 7 d. However, after 45 and 60 min isolation, aortic occlusion resulted in significant rise in serum enzyme and tissue TBARS measures as well as poor survival (14% and 0%, respectively). In contrast, all rats survived even after 60 min of THVE.

CONCLUSIONS

THVE was tolerated up to 60 min with less reperfusion injury and better survival than celio-mesenteric arterial occlusion and supraceliac aortic occlusion in the rat, if needed, aortic clamping should not exceed 30 min. Beyond that, selective celio-mesenteric arterial occlusion may be considered.

Thrombotic effect of purposeful back-wall stitch for different suture locations and vessels in rats

Many microsurgeons experience inadvertent back-wall stitch as a cause of immediate anastomotic failure. To investigate this factor as a possible cause of delayed arterial anastomotic failure that does not appear in the operation room, a purposeful back-wall stitch (PBWS) model of microarterial anastomosis was applied in various configurations on femoral and carotid arteries of rats. Carotid (n = 28) and femoral (n = 28) artery groups were equally divided into 4 different subgroups according to the type of PBWS. Control subgroups had no PBWS. Thirty-degree, 60-degree, and 90-degree subgroups had PBWS located at 30, 60, and 90 degrees, respectively. Patencies were assessed at 60 minutes and 24 hours. Immediate milking test demonstrated normal anterograde refilling in all anastomoses. PBWS increased thrombosis in femoral arteries, while it did not increase it in the carotid at either evaluation times. The only significant difference was between 90 degrees PBWS and the control subgroup irrespective of the vessel factor in 24 hours. Histologic examination supported absence of thrombosis, as suggested by surgical examination. This may show that small-sized arteries are more inclined to thrombosis compared with larger ones and the thrombosis risk increases as the inadvertent back-wall stitch is more centrally located. Contrary to general notion that the inadvertent back-wall stitch causes immediate thrombosis, thromboses later than 1 hour, and even patent anastomoses in 24 hours, were observed in femoral and carotid artery groups. This study suggests that the inadvertent back-wall stitch should also be considered as a possible cause of late anastomotic problems.

Catheter occlusion technique to facilitate distal anastomoses using vein grafts

Several different modes of achieving a bloodless operating field by proximal and distal occlusion of blood vessels have been described. Vascular clamps, vessel loops, intraluminal occluding devices, and tourniquets have been used to control the tibial and pedal vessels but may cause injury or fail to control heavily calcified arteries. We describe an alternative way to control proximal and distal small arteries by using small, umbilical vein, feeding catheters. The catheters are introduced in the proximal and distal arterial lumen and in the vein graft lumen, achieving hemostasis, technically facilitating the suturing, and providing a means for the administration of vasodilator or thrombolytic agents as well as for a completion angiography.

Effect of the two-wall-stitch mistake upon patency of rat femoral vein anastomosis: Preliminary observations

Anastomotic patency is believed to be the most important factor in microvascular surgery. The two-wall stitch is a technical error commonly considered to cause thrombosis of the anastomosis, especially on the venous side. In order to demonstrate the real effect on vein patency of the two-wall stitch, the authors performed a standardized mistake after correct microanastomosis on the femoral vein of 15 rats, with one stitch passing through the whole thickness of the two walls of the vein. Traditional correct anastomoses on the contralateral side were used as controls. Patency was assessed at 5, 20, and 60 min and at 24 h by the milking test, and by direct section of the vessel at 24 h. The results showed no statistically significant difference between the two techniques. Histological examination confirmed the clinical judgment about the vessel's patency, and ultrastructural microscopy evidenced only mild signs of endothelial activation. In conclusion, this study indicates that the occasional two-wall stitch does not necessarily increase the risk of venous occlusion in anastomoses of the rat femoral vein.

Short-term postoperative flow changes after free radial forearm flap transfer: possible cause of vascular occlusion

The risk for free flap thrombosis is greatly influenced by blood flow. Postoperative hemodynamic changes in vascular pedicles of the microvascular skin flap have not been reported, however. This study focuses on the intraoperative and postoperative changes in the flow volume in the vascular pedicles of the free forearm flap examined by color Doppler ultrasonography. The arterial flow volume increased continuously until day 7, compared with which, the volume after flap elevation was 36%. On day 1, it reached only 52%. In the venous pedicle, the flow volume through the cutaneous vein was only 37% compared with that through the radial vena comitans after flap elevation, whereas the volume through both veins was equal on day 7. Drastic changes in the flow explain the possible vascular occlusion during the early postoperative period in the free forearm flap transfer.

Immunohistochemical evaluation of failed vessel anastomoses in clinical microsurgery

Failed vessel anastomoses collected from 12 patients during elective free flap surgery, and from one patient after failed mid-hand replantation were subjected to immunohistochemical analysis. The anastomotic failure was due to an obvious thrombosis, poor flow, an excessively sharp pulse or some other reason causing a non-functioning anastomosis. A total of 17 samples were obtained, 13 of them arterial, three between the artery and vein graft, and one venous. The majority of samples were resected during primary surgery and four of them at reoperation. Variables of coagulation and fibrinolysis were analysed repeatedly during the operation in 7/13 patients. Total occlusion was seen in 6/17 samples and a non-occlusive thrombus in 4/17; two of these were due to suture error. Immunohistochemistry showed that, overall, the endothelial cells (PECAM-l, CD 31) were absent and that the staining pattern for platelets (CD 42b and CD 31) and fibrin (fibrin II, T2G1) correlated. In the absence of a thrombus, however, adherent platelets were positive only for CD 42b, not for PECAM-1. Vessel inflammation was a prominent feature at reoperations. Analysis of coagulation and fibrinolytic markers (thrombin-antithrombin III complex, prothrombin fragment 1 + 2 and D-dimer) confirmed the occurrence of thrombosis in three patients undergoing breast reconstruction with clinically obvious thrombosis during primary surgery or at reoperation. Moreover, the patients with active cancer (2/7) were clearly hypercoagulable compared with the other patients. In short, the primary anastomotic failure was associated with loss of endothelial cells, and with co-localised platelet recruitment and fibrin formation at these sites. At reoperation, inflammation was a prominent feature at the vessel site of thrombi.