David Smith
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Background
Platelet microvesicles (PMV) are circulating phospholipid-rich particles generated by the exocytic budding of the cell membranes of activated platelets. They are at low levels in normal plasma. Elevated levels of PMV are associated with vascular dysfunction, thrombosis and inflammation.
The combination of cardiopulmonary bypass (CPB) and cardiac surgery is responsible for abnormal haemostasis and a significant incidence of excessive post-operation haemorrhage. However, to date, little is known about PMV numbers or phenotype during CPB. Given that PMV express proteins involved in the control of coagulation, they may be important in the maintenance or alteration of haemostasis during CPB.
Aims
The principal objective of this work is to characterise PMV produced during cardiac surgery in terms of their numbers and surface protein expression, how these change during and after surgery, and how they are affected by co-morbid disease (such as diabetes) and antiplatelet agents.
The secondary objective is to investigate whether there is a relationship between the number and type of PMV produced during cardiac surgery, and the extent of postoperative bleeding.
Method
This is an observational longitudinal study of 400 adult patients during cardiac surgery. Each patient acts as their own control. Seven paired blood samples (one arterial, one venous) will be taken between induction of anaesthesia and the first postoperative day to examine the time course of PMV activity, using flow cytometry, during the perioperative period. These data will then be correlated with demographic details including preoperative anti-platelet therapy, nature of the cardiac disease (e.g. CABG versus valve surgery), and the extent of postoperative bleeding.
