Protective effects of antithrombin on free groin flaps after secondary venous stasis in the rat model

Abstract

Background: The anticoagulant activity of heparin is well established and led to its widespread clinical use for the prophylaxis and treatment of venous thrombosis in microsurgery. Heparin accelerates antithrombin (AT)-mediated inhibition of clotting and fibrinolytic proteinases.

Aim: The aim of the study is to determine whether the focussed delivery of AT by rinsing of free adipocutaneous groin flaps shows protective effects on flap survival, following a fatal secondary venous stasis in the rat model. Further, intravital video microscopy (IVM) is used to detect substance-specific alterations in microvascular perfusion with special focus on regional differences between central and peripheral flap regions.

Methods: Free microvascular groin flaps (n = 22) were transplanted to the neck in adult Sprague-Dawley rats. The flap pedicle was re-explored and the distal stump of the flap artery was catheterised 20 h later. Animals in group I (n = 11) were treated with 1 ml of Ringer's solution administered over 10 min via intraarterial infusion. Those in group II (n = 11) received 1 ml of AT (50 IU/kg). Afterwards, the flap vein was clamped for 35 min. The skin of the flaps and the native contralateral groin was examined by IVM using the plasma-marker fluorescein isothiocyanate (FITC)-dextran and carboxyfluorescein diacetate succinimidyl ester (CFDA-SE)-labelled thrombocytes. After 14 days, the viability of the flaps was evaluated.

Results: The treatment with AT significantly increased the functional capillary density (FCD) of the flaps. After 14 days, flap necrosis occurred in nine animals of group I and three animals of group II, respectively. No partial flap loss was detected.

Conclusions: The focussed delivery of AT resulted in significantly improved flap salvage. The results may reinforce the clinical custom of AT substitution in the setting of major surgical procedures such as elaborate microsurgical reconstructions, at least in cases with diminished AT levels.

Keywords: Antithrombin (AT); Antithrombin III (AT-III); Free flap; Groin flap; Intravital microscopy (IVM); Ischaemia; Microsurgery; Rat model; Reperfusion (I/R).