Antithrombotic medications are routinely used in the postoperative management of microvascular free flaps in head and neck reconstruction. However, there is no consensus in the literature on the optimal regimen, and studies have shown mixed results regarding the risk of postoperative hematoma. In this study, we aim to explore whether antiplatelet or anticoagulant therapy increase the risk of postoperative hematoma formation or transfusion requirement in patients undergoing free flap reconstruction.
METHODS: A multi-institutional retrospective chart review was performed on all patients who underwent a microvascular free flap of the head and neck between August 2013 to July 2021. Perioperative use of anticoagulation or antithrombotics, intra-operative heparin bolus, postoperative day 0 hypertension (systolic blood pressure (BP) > 150 or diastolic BP > 100 for two consecutive readings or systolic BP >200 once) and postoperative platelet count data were collected for each patient. Primary endpoints were rate of post-operative hematoma and rate of post-operative packed red blood cell transfusions. GraphPad Prism 9.2.0 was used to perform univariate and multivariate analysis reported with OR (95% CI), p-value.
RESULTS: A total of 798 microvascular free flaps were performed. The overall rate of hematoma was 5.8% (n=46). The overall rate of transfusion was 22% (n=179). The risk of postoperative hematoma formation was not affected by prophylactic postoperative antithrombotic therapy with aspirin (81mg or 325mg), preoperative or postoperative anticoagulation (enoxaparin or heparin), the presence of POD0 hypertension, postoperative platelet count, or intra-operative heparin bolus on both univariate and multivariate analyses. On univariate analysis, aspirin (325mg) (1.42 (0.9972-2.013), p=0.049) and subcutaneous heparin (2.462 (1.724-3.511), p<0.001) increased risk of transfusion, while enoxaparin decreased risk of transfusion (0.4174 (0.2743-0.6405), p<0.001). On multivariate analysis, only subcutaneous heparin remained significant for increased risk of transfusion (1.920 (1.133-3.196), p=0.013).
CONCLUSIONS: Our results confirm previous studies showing that neither prophylactic anticoagulation with heparin or enoxaparin nor antiplatelet therapy with either 81mg or 325mg aspirin increases the risk of post-operative hematoma formation even when accounting for other risk factors for hematoma formation. In addition, our results suggest that 325mg aspirin and subcutaneous heparin increase a patient’s risk of postoperative transfusion, while enoxaparin appears to decrease a patient’s risk. No studies to date specifically compare antithrombotic regimens and transfusion rates in head and neck reconstructive cases, several have reported adverse outcomes in patients receiving transfusions including increased surgical and medical complications and longer length of stay. Our results highlight the potential risk of 325mg aspirin and subcutaneous heparin in the postoperative period. Enoxaparin may be the preferred postoperative anticoagulant in free flap patients compared to subcutaneous heparin but further study is needed.