An evaluation of two activated clotting time monitors during cardiac surgery

The activated clotting time (ACT) is a commonly used method for assessing the degree of anticoagulation during cardiac surgery. Two automated ACT monitors were evaluated in 29 adult patients undergoing cardiac surgery. The HemoTec ACT monitor (HTC; HemoTec, Inc., Englewood, CO) was evaluated using 0.8 ml of whole blood in dual-chamber, high range kaolin cartridges. The Hemochron ACT monitor (HCH; International Technidyne, Inc, Edison, NJ) was evaluated using 2.0 ml of whole blood in glass tubes with diatomaceous earth activator. Following sternotomy, a coagulation profile consisting of HTC, HCH, and a partial thromboplastin time (PTT) was obtained (T0). Beef lung heparin was administered in 3 consecutive doses: 40 units/kg (T1), 80 units/kg (T2), and 180 units/kg (T3). Coagulation profiles were drawn 5 minutes after each dose. Following cardiopulmonary bypass (CPB), coagulation profiles were drawn 15 minutes (T4), 2 hours (T5), and 24 hours (T6) after the protamine dose. HTC and HCH ACT values differed significantly at T1, T2, and T4 (p less than 0.001). In the pre-CPB period, the HCH ACT correlation with PTT divided by its control value (PTT/CTL) (r = 0.73) was significantly better (p = 0.02) than the correlation of HTC ACT with PTT/CTL (r = 0.41). In the post-CPB period, both HCH ACT (r = 0.45) and HTC ACT (r = 0.30) correlated weakly with PTT/CTL. In the bias analysis, the limits of agreement (of all HCH and HTC ACT values) showed that HTC ACT is between 61% and 133% of the HCH ACT value in 95% of determinations.(ABSTRACT TRUNCATED AT 250 WORDS)