The effect of stasis on a microvascular anastomosis

Analysis of Operation Duration in Thoracodorsal Artery Perforator Free-Flap Surgery of the Lower Extremities

PURPOSE

This retrospective study aimed to identify the factors that affect the duration of thoracodorsal artery perforator (TDAP) free-flap surgery and to offer strategies for optimizing the surgical procedure.

METHODS

We analyzed 80 TDAP flap surgeries performed by a single surgeon between January 2020 and December 2022, specifically focusing on free flaps used for lower-extremity defects with single-artery and single-vein anastomosis. The operation duration was defined as the time between the surgeon's initial incision and completion of reconstruction. Linear regression analyses were conducted to identify the factors affecting operation duration.

RESULTS

The average operative duration was 149 minutes (range, 80-245 minutes). All flaps survived, although 8 patients experienced partial flap loss. The operative duration decreased with increasing patient age and when end-to-end arterial anastomosis was performed. However, the risk increased with larger flap sizes and in patients with end-stage renal disease.

CONCLUSIONS

Our study identified several factors and methods that could accelerate TDAP free-flap procedures. These findings offer valuable insights for optimizing surgical processes and improving overall surgical outcomes. Although further research is needed to confirm and expand upon these findings, our study provides important guidance for surgeons in developing effective strategies for TDAP flap surgery.

One Versus Two Veins in Free Anterolateral Thigh Flap Reconstruction: A Systematic Review and Meta-Analysis

There is considerable debate in the literature as to whether one or two venous anastomoses are optimal in the anterolateral thigh (ALT) free-flap reconstruction. The literature is currently devoid of a systematic review and meta-analysis of studies evaluating these procedures. This review will therefore be the first to address this clinical question. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, two authors (EW and SR) independently searched the following electronic databases: MEDLINE, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials (CENTRAL). Case-control, randomised control and observational studies were included. The authors did not include case reports, case series, letters or abstracts. All patients were included regardless of age, co-morbidity status, and the anatomical site of reconstruction. Venous congestion/thrombosis, flap take-back rate due to venous insufficiency, flap loss and operative time were the primary outcome measures. Secondary outcome measures included partial flap loss and haematoma formation. The Newcastle Ottawa Scale was used to assess the risk of bias in the included studies. Review Manager 5.4 data synthesis software was used for the analysis. The authors identified eight observational studies, with a total of 1741 patients reviewed, demonstrating a significantly lower flap take-back rate for a double venous anastomosis and a shorter operative time in the single venous anastomosis group. However, other reported measures, including venous congestion and flap loss, showed a non-significant difference (P>0.05). The limitations of the evidence included in this review were that all studies were observational in design. The flap take-back rate is significantly less when anastomosing two veins, and the authors recommend that utilising a second vein can circumvent the caveat of venous compromise.

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.

One versus two venous anastomoses in microvascular lower extremity reconstruction using gracilis muscle or anterolateral thigh flaps

INTRODUCTION

Free tissue transfers are a highly reliable procedure routinely performed for reconstruction of a wide range of defects. Main complication in free flap surgery is usually venous thrombosis. Many technical controversies exist regarding the technical details of the microvascular anastomosis in order to prevent occurrence of thrombosis and optimize outcomes. We therefore evaluated our results regarding the execution of one versus two venous anastomoses in a variety of free flaps (fasciocutaneous- or muscle free flap) utilized for lower limb reconstruction.

PATIENTS AND METHODS

Between 2009 and 2015, 354 patients underwent 386 free ALT- or gracilis flaps for lower limb defect reconstruction after trauma, infection, or malignancies at our institution. The data was retrospectively screened for patients' demographics, perioperative details, flap survival, and surgical complications. The cases were divided into two groups regarding the number of microsurgically performed venous anastomosis: one versus two veins.

RESULTS

Regarding the preoperative evaluation, there were no significant differences regarding comorbidities between the two groups. Overall, there was no significant difference regarding the rate of major (1 vein: 20.38% versus 2 veins: 18.78%, p>0.05) and minor (1 vein: 1.27% versus 2 veins: 2.18%, p>0.05) surgical complications during our 3-months follow-up period. Major complications included total flap losses of 5.73% (1 vein) versus 8.78% (2 veins).

CONCLUSION

This study analyzed a large series of microsurgical reconstructions, with a focus on the impact of the number of venous anastomosis. The findings suggest that successful free tissue transfer for lower limb reconstruction can be achieved independent of the number of venous anastomoses, however two should be performed when technically feasible.

The effect of botulinum toxin B pretreatment to the blood flow in the microvascular anastomosis

BACKGROUND

Although multiple factors can lead to free flap failure, vessel-related accidents are the most important. Many methods have been developed (both intraoperative and postoperative) to prevent vessel-related complications. In this article, we study the effects of a "preoperative treatment" using botulinum toxin B that could enhance the velocity and blood flow of vascular pedicles and decrease vascular accidents.

METHODS

Ten Sprague-Dawley rats were pretreated with botulinum toxin type B at the perivascular area of the femoral vessel. Ten other rats were injected with saline as a control group. After 3 days, pedicle diameter and the peak mean frequency of blood in the pedicle were measured using laser Doppler flowmetry, and the peak mean blood velocity was calculated. We performed a "pedicle division and reanastomosis" operation to compare changes in vessel diameter and peak mean blood velocity.

RESULTS

Vessel diameter was significantly increased in the botox-pretreated group for both veins and arteries. A comparison of the deep femoral vein and artery blood velocities showed that the peak mean velocity was significantly higher in the botox group. The average increase in blood velocity was significantly larger in the botox group.

CONCLUSIONS

Botulinum toxin B is helpful by influencing the microvascular environment through an increase in the blood velocity of the pedicle.

One versus two venous anastomoses in microvascular free flap surgery

BACKGROUND

The authors' goal was to determine whether one or two venous anastomoses results in superior blood flow through microvascular free flaps.

METHODS

During flap harvest, blood velocity was measured in each of two venae comitantes using Doppler ultrasonography. Next, one of the two veins was occluded with a microvascular clamp and blood velocity was measured in the open vein. The clamp was then removed and placed on the other vein, and blood velocity was measured in the first vein. The pedicle was divided and microvascular anastomosis of either one or two veins was performed. Venous blood velocity was then compared between flaps with one versus two venous anastomoses.

RESULTS

Eighty-one free flaps were performed. Before pedicle division, the peak venous blood velocity in each of the two venae comitantes averaged 6.3±4.8 cm/second. When one of the veins was occluded, the peak venous blood velocity increased to 19.5±17.3 cm/second (p<0.00001). One venous anastomosis was performed in 69 flaps and two venous anastomoses were performed in 12 flaps. The mean blood velocity in flaps in which one venous anastomosis was performed was greater than the mean blood velocity in either vein when two venous anastomoses were performed (13.1±7.3 cm/second versus 7.5±4.3 cm/second, respectively; p=0.001).

CONCLUSIONS

When one vena comitans is occluded, blood velocity in the second vena comitans increases significantly. Venous blood velocity is significantly greater after a single venous anastomosis than in either of two veins when two venous anastomoses are performed. These results argue against routinely performing two venous anastomoses.

Influence of topical heparin on stasis-induced thrombosis of microvascular anastomoses

An experiment was done to determine whether topical heparin and the association of anastomoses with dependent tissue (free flaps) exert any influences on stasis-induced microvascular thrombosis. Rat femoral vessel anastomoses with or without free flap construction were used in a total of 50 male Sprague-Dawley rats. Saline either with or without heparin was used for intralumenal irrigation during the anastomosis. Following anastomotic repair, the femoral vessels were reclamped, inducing stasis for either 2 or 4 hr. Our results showed that static blood had little adverse effect on thrombosis at the arterial anastomosis when reclamped for up to 4 hr in both standard and flap-associated anastomoses. Topical heparin significantly reduced the incidence of stasis-induced thrombosis of venous anastomoses. The venous patency rates in standard anastomoses were lower than those in flap-associated anastomoses after both 2 and 4 hr of stasis. From these results, we conclude the following. 1) Arteries may be reclamped for up to 4 hr without detriment despite static blood being in contact with the anastomotic site. 2) Topical heparin may be helpful in increasing the patency rate of venous anastomoses after a period of blood stasis. 3) Free flap construction may play a role in decreasing stasis-induced microvascular thrombosis.