Improved Microsurgical Anastomotic Patency with Low Molecular Weight Heparin

Abstract

Blood flow to a free flap may be impaired by thrombotic occlusion at the anastomosis or by microemboli occluding microvessels. The purpose of this study was to test the hypothesis that unfractionated heparin (UFH) or low molecular weight fractions of heparin (LMWH) could improve both the patency of microvascular anastomoses and microcirculatory perfusion. Sixty-six rats underwent orthotopic elevation of 3- x 10-cm epigastric free flaps. Animals received a single injection of either vehicle, UFH or LMWH, prior to microvascular clamp application and pedicle division. Anastomotic patency and tissue survival area were assessed on postoperative day 7. Anastomotic patency was significantly improved in both the UFH and LMWH groups. Total tissue survival area in those flaps with anastomotic patency was significantly improved in the UFH and the LMWH groups. Although both UFH and LMWH significantly elevated activated partial thromboplastin times (APTT) and anti activated clotting factor X (anti-Xa) activity over controls, UFH had its greatest effect on APTT, and LMWH on anti-factor Xa activity. Hematomas developed only in the UFH group. Thus, although both UFH and LMWH improved microcirculatory perfusion, as indicated by increased flap survival, only LMWH improved anastomotic patency while minimizing hemorrhage.

Anticoagulation Therapy in Microsurgery: A Review

“…Although some studies clearly have found LMWH to be a less effective treatment than traditional heparin in reducing the frequency of arterial thrombosis, 46,47 others have reported better or equal results. 34,48 In a rabbit model Zhang et al 48 observed a 50% increase in the patency of arterial anastomoses with LMWH in comparison with no anticoagulation, but observed no difference in the patency of small venous anastomoses.…”

Comparative study of isovolemic hemodilution with 3% albumin, dextran-40, and prophylactic enoxaparin (LMWH) on thrombus formation at venous microanastomosis in rats

“…Experimental studies in rats have demonstrated better results on prevention of microanastomosis thrombosis using LMWH, but often with a dose greater than the typical human dose. 28,29 We observed that de 0.5 mg/kg/day dosage of enoxaparin (similar that used in prophylaxis of thromboembolism in adult human, 40 mg/day) was not adequate to prevent thrombosis in femoral vein microanastomosis in rats.…”

The use of microvascular free flaps in head and neck reconstruction performed by the otorhinolaryngologists: a series of 65 flaps

“…Her üç ajanın da antikoagülan etkinliği in vitro deneyler dışında, periferik vasküler cerrahiler ve çeşitli hayvan çalışmala-rında gösterilmiştir; ancak MSDF ile ilgili klinik etkinlikleri gösterilememiştir. [21][22][23][24] Bu çalışma-nın yapıldığı merkezdeki MSDF ile ilgili cerrahlar, olası flep kaybının hasta ve doktor açısından getireceği korkunç senaryo ile karşılaşmaktan-sa, yeterli deneyim sahibi olunana kadar, flebin kaybedilmesi ile alakalı tüm riskleri minimize edecek şekilde antikoagülan tedavinin kullanıl-ması gerektiğini düşünmektedirler.…”