Effect of Low Dose Aspirin on Thrombus Formation at Arterial and Venous Microanastomoses and on the Tissue Microcirculation

Abstract

In free flap/replantation surgery, failure is usually associated with thrombotic occlusion of a microvascular anastomosis (risk zone I) or, on occasion, flow impairment in the microcirculation of the transferred or replanted tissue (risk zone II). The objective of this study is to describe the effect of low dose aspirin on blood flow at both risk zones in microvascular surgery. Risk zone I: In rat femoral arteries and veins, thrombus formation was measured at the anastomoses using transillumination and videomicroscopy. Forty male Wistar rats were assigned in equal numbers to four groups: either arterial or venous injury with either aspirin (5 mg/kg systemically) or saline treatment. We found that aspirin significantly reduces thrombus formation at the venous anastomosis (p = 0.001). Risk zone II: In the isolated rat cremaster muscle downstream from an arterial anastomosis, we measured capillary perfusion, arteriolar diameters, and the appearance of platelet emboli for 6 hours in the muscle microcirculation. Sixteen male Wistar rats in two equal groups received either aspirin (5 mg/kg systemically) or saline. We found that in aspirin-treated animals, capillary perfusion is significantly (p = 0.002) improved, whereas arteriolar diameters and emboli only slightly increased. In conclusion, low dose aspirin inhibits anastomotic venous thrombosis and improves microcirculatory perfusion in our rat model. These studies provide quantitative data confirming and clarifying the beneficial effects of low dose aspirin in microvascular surgery.

A Review of Thrombosis and Antithrombotic Therapy in Microvascular Surgery

“…Kort et al [40] observed that when administered 30 min prior to surgery aspirin had no antithrombotic effect, while other authors describe a significant increase in vessel patency when administered 10 h preoperatively [41]. Low-dose (5 mg/kg) aspirin has been shown to be sufficient to irreversibly block platelet thromboxane production while at the same time preserving endothelial prostaglandin I 2 and other antithrombotic prostaglandin synthesis [42]. …”

Impact of poor microsurgical suture technique on tissue perfusion in a rat model

“…However, the difference between experimental groups in capillary perfusion, measured as capillaries per visual field, proved that the inverting suture as a poor anastomosis technique caused a significant decrease in tissue perfusion over 24 h. This prolonged reduction in tissue perfusion was most likely due to microthrombosis secondary to dislodging of microemboli from the thrombogenic suture site, as was demonstrated in other studies. 3,8,15 We may conclude that in free-tissue transfer and any other case of smallvessel anastomosis, patency of the main vessels and blood flow is not a sufficiently predictive parameter for evaluation of peripheral tissue perfusion.…”

Investigation of Antithrombotic Drug Effects on Preventing Thrombosis Emerging in Gluteus Maximus Flaps before Anastomosis

“…However, Peter emphasized that low dose aspirin (5mg/kg systemically) inhibits anastomotic venous thrombosis and improves microcirculatory perfusion in their rat model after provided quantitative data confirming and clarifying the beneficial effects of low dose [10].…”