Improving free-flap survival using intra-operative heparin: Ritualistic practice or evidence-base medicine? A systematic review

Abstract

The failure rate of free flaps is approximately 5%, mostly due to thrombosis of microvascular anastomosis. A number of pharmacological agents have been tested in order to enhance the patency of microvascular anastomosis and so to as extend the survival of free flaps. One of them is heparin, a very commonly used anticoagulant. However, there exists no consensus on its use in microsurgery as concerns time of introduction (pre-, intra- or post-operative), recommended dosage, or duration of utilization. The aim of this study was to determine whether or not the use of intra-operative heparin, in its systemic or topical forms, can bring about improved survival of free flaps, and if and when it should be recommended in microsurgery. A systematic review on the PUBMED database enabled us to identify articles evaluating the benefits of intra-operative heparin with regard to free-flap survival. All in all, fifteen articles in animal and human research were selected. As far as animal research is concerned, 9 studies out of 11 showed the superiority of topical intra-operative heparin compared to saline in improving free-flap survival rates through improved patency of the anastomosis. As regards systemic intra-operative heparin, on the other hand, only two trials out of four yielded favorable results. In clinical research in humans, there has been no prospective randomized trial studying the action of topical intra-operative heparin in vessel irrigation of ex-vivo free flaps before vascular repermeabilisation. However, the preliminary results of four trials seem to provide positive arguments for this practice. The use of systemic per-operative heparin (intravenous injection) does not improve the survival of free flaps in either animal models or humans. In animal models, however, the use of topical intra-operative heparin (vessel irrigation) has been shown to improve the free-flap survival rate by avoiding thrombosis of microvascular anastomosis. Finally, in clinical studies concerning humans, as of now no prospective randomized trial has proven that use of topical intra-operative heparin to ensure vessel irrigation in ex-vivo flaps is likely to increase free-flap survival. Studies should be conducted to decide whether or not to validate a rather ritualistic practice that consists in irrigating the relevant vessels before anastomosis; does it or does it not improve the patency rate?