title: Regulation of fibrinolysis in aortic surgery.
abstract: The existence of inhibitors of plasminogen activator has been shown to play an important role in regulation of fibrinolysis and postoperative thrombosis. Platelets and endothelium are sources of plasminogen activator inhibitor (PAI). This study determines the contribution of platelet-released PAI to perioperative fibrinolytic shutdown. PAI levels were measured in 25 patients having aortic surgery. In nine patients the platelet-released PAI contribution was determined by in vitro activation of platelets with phorbol-myristate-acetate (PMA). Mean preoperative PAI levels (3.78 +/- 1.19 U/ml) were similar to controls (3.01 +/- 1.04 U/ml) (p greater than 0.05). Plasma PAI showed an operative increase to a maximum at 8 hours postoperatively and returning to preoperative values by the second postoperative day. In the nine patients who were subjected to studies with in vitro activation, the preoperative PAI level (4.0 +/- 0.9 U/ml) was elevated to 5.1 +/- 0.7 U/ml (p = 0.001) with PMA induction. Maximum stimulated release of platelet granule contents (platelet releasate) could account for an increase of only 1.0 U/ml compared with a postoperative increase of 2.3 U/ml. Postoperative mean peak plasma PAI (6.3 +/- 0.4 U/ml) could not be further elevated by induced release (6.3 +/- 0.4 U/ml) (p = 0.003). A statistically significant increase in PAI occurred in aortic surgery patients postoperatively. The platelet releasable pool of PAI contributed to the increase and was functionally exhausted postoperatively. Postoperative increases of PAI were twice that induced by platelet in vitro stimulation alone. The perioperative increase in PAI was partly due to platelet release.
mesh_terms: D001011:Aorta / Q000601:surgery; D001014:Aortic Aneurysm / Q000097:blood / Q000601:surgery*; D001018:Aortic Diseases / Q000097:blood / Q000601:surgery*; D001807:Blood Vessel Prosthesis; D005342:Fibrinolysis; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors*; D015849:Plasminogen Inactivators
chemical_list: D006023:Glycoproteins; D015849:Plasminogen Inactivators; D010960:Plasminogen Activators