RESUMO
OBJECTIVE: The activated clotting time (ACT) is used worldwide to confirm safe heparin anticoagulation for cardiopulmonary bypass. For the present study, the performances of 2 commonly used ACT devices were compared with each other and with anti-Xa levels throughout the surgical procedure in order to understand whether they can be used interchangeably. DESIGN: Prospective study. SETTING: Tertiary care center. PARTICIPANTS: The study comprised 33 elective adult cardiac surgical patients. INTERVENTIONS: Blood samples were taken at standard times throughout the surgery (after induction, after heparin bolus, 4 samples at 30-minute intervals during cardiopulmonary bypass, after protamine), and ACTs and anti-Xa levels were analyzed. Data were compared using receiver operating characteristics and LOESS regression. MEASUREMENTS AND MAIN RESULTS: The correlation between anti-Xa levels and the Hemochron ACT (Instrumentation Laboratory, Bedford, MA) was acceptable (râ¯=â¯0.82, 95% confidence interval [CI] 0.757-0.868; p < 0.0001), as was the correlation between anti-Xa levels and the i-STAT (Abbott Point of Care, Abbott Park, IL) (râ¯=â¯0.81, 95% CI 0.738-0.858; p < 0.0001). The correlation between the 2 ACT methods was poorer (râ¯=â¯0.77, 95% CI 0.707-0.828; p < 0.0001) than their correlation to anti-Xa levels. When compared with anti-Xa levels, the sensitivity and specificity were mediocre for both devices, although the i-STAT performed better than the Hemochron ACT. The Hemochron ACT read higher values than the i-STAT ACT throughout the course of the surgery. CONCLUSION: The correlation between the Hemochron ACT and i-STAT ACT is moderate, and they have different sensitivity and specificity when compared with anti-Xa levels. This suggests that ACT devices should not be used interchangeably, but cut-off values for safe anticoagulation during cardiopulmonary bypass should be determined for each type of device, particularly when switching supplier.