Toward Optimal Anticoagulation Monitoring During Cardiopulmonary Bypass: It Is Still A Tough “ACT”

ACTIVATED CLOTTING time (ACT) is regarded as the gold standard for measurements of heparin anticoagulation during cardiopulmonary bypass (CPB). ACT is a widely available, inexpensive point-of-care (POC) test and can be performed by nonlaboratory staff with minimal training. Despite its routine use since the 1970s, optimal ACT target remains unclear due to the lack of high-level evidence. Recent international surveys consistently reported that many institutions use ACT targets between 400 and 500 seconds for safe CPB management, but a relevant number of cardiac centers aim for ACT values <400 or >500 seconds. Such variations in ACT targets among institutions are partly explained by (1) device use instructions; (2) different coagulation activators (kaolin, celite, etc) and different technologies of ACT analyzers; and (3) types of CPB circuits (eg, surface coating, use of cardiotomy suction) and potential invasiveness of surgery. Of note, fluctuating coagulation factor levels, platelet count and function, and temperature may yield variable ACT values at the same heparin activity.

In this issue of the Journal of Cardiothoracic and Vascular Anesthesia, Falter et al. compared the results of 2 POC cartridge-based ACT analyzers, Hemochron (Werfen, Bedford, MA) and iSTAT (Abbott, Princeton, NJ), at several time points during elective cardiac surgery in 33 patients. ACT values from the 2 devices were also compared with anti-Xa activity. The authors found an acceptable correlation between anti-Xa and Hemochron ACT (r = 0.82, 95% confidence interval [CI] 0.757-0.868), as well as between anti-Xa and iSTAT ACT (r = 0.81, 95% CI 0.738-0.858). Interestingly, the correlation between the 2 ACT devices was lower (r = 0.77, 95% CI 0.707-0.828). The authors concluded that the ACT results from different devices are not interchangeable and that target values for safe anticoagulation on CPB should be determined specifically for each device and potentially adapted with change of the device.

A switch from ACT to anti-Xa monitoring cannot be recommended in cardiac surgery with CPB at the moment.