Fibrin clot susceptibility to lysis is impaired after on-pump coronary artery by-pass grafting with tranexamic acid: clinical implications.

Abstract

Coronary artery bypass grafting (CABG) done on-pump may cause a significant blood loss. Low fibrinogen is associated with perioperative bleeding. The influence of cardiopulmonary bypass on fibrin clot properties is poorly investigated. We studied 55 patients with isolated coronary artery disease on aspirin undergoing on-pump CABG with tranexamic acid. Fibrinogen levels, fibrinolytic capacity expressed as clot lysis time (CLT), thrombin generation potential and platelet count were assessed before and after the surgery (prior to admission to the intensive care unit). A postoperative drop in haemoglobin (-30% from baseline), haematocrit (-31% from baseline) and platelet count (-42% from baseline) was observed (all, P < 0.0001). Postoperative fibrinogen level was lower by 57%, compared with preoperative value (1.5 [1.3-1.8] vs. 3.5 [2.8-3.9] g/l, P < 0.0001). Postoperative CLT was longer by 48 min, compared with preoperative (182 [170-218] vs. 134 [122-165] min, P < 0.0001). Thrombin generation was impaired postoperatively: both lag time and time to peak thrombin were prolonged by 44 and 45%, respectively, whereas endogenous thrombin potential and peak thrombin generation decreased by 45 and 78%, respectively (all P < 0.0001). Median postoperative drainage at 12 h was 400 [290-570] ml. Predictors of blood loss at 12 h identified in multivariable linear regression model adjusted for sex and preoperative fibrinogen level were: BMI (b = -23.4, P = 0.048) and postoperative CLT (b = -2.4, P = 0.042). Despite decreased fibrinogen levels after on-pump CABG with tranexamic acid, fibrin clot susceptibility to lysis is impaired, as reflected by prolonged CLT. Postoperative CLT is associated with mediastinal drainage at 12 h.