Plasma von Willebrand factor and antithrombin III in patients submitted to open heart surgery.

Cardiovascular surgery for valve replacement led to a significant (p < 0.001) increase of plasma von Willebrand factor antigen level from 227% +/- 30.9 (x +/- SEM) recorded before surgery, to 397% +/- 40.7 at the end of the surgical procedure and the levels of this endothelia-derived glycoprotein remained high (427% +/- 38.9) 48 hours later. On the other hand plasma antithrombin III activity decreased from 85.4% +/- 8 before surgery, to 67.0% +/- 6 at the end of the surgical intervention and rose to 81.3% +/- 7, two days later. Lethal outcome occurred in a patient with initial low antithrombin III level (62%). These observations stress the importance of a thorough investigation of hemostatic variables in patients submitted to cardiovascular surgery.