Postoperative elevation of human peripheral blood monocyte tissue factor coagulant activity

The generation of tissue factor coagulant activity was measured in short-term cultures of mixed mononuclear cells prepared from peripheral blood. Levels of tissue factor activity were significantly increased (P less than 0.05) at 3 and 7 days after surgery in patients who had had uncomplicated surgical procedures when comparison was made with preoperative levels and with levels observed at the same time intervals in patients who had had a general anesthetic without surgery. Activity in patients who had had surgery returned to preoperative levels at 14 days after surgery. Findings were similar whether or not phytohemagglutinin was added to the cultures to enhance tissue factor generation and whether or not tissue factor activity was quantified on the basis of activity per culture or per monocyte. No change in monocyte counts occurred in the interval during which these studies were performed. Because the increase in monocyte tissue factor activity coincided with the interval after surgery when patients are known to be at greatest risk of thromboembolism, we postulate that the capacity of monocytes to generate increased tissue factor activity may contribute to postoperative hypercoagulability.