During cardiopulmonary bypass, what is the typical activated clotting time (ACT) target to maintain anticoagulation?

• A. A target ACT during CPB is greater than 420 seconds.
• B. A target ACT during CPB is greater than 480 seconds.
• C. A target ACT during CPB is greater than 360 seconds.
• D. A target ACT during CPB is greater than 600 seconds.

Answer: (B)

During cardiopulmonary bypass, the blood is routed through an artificial circuit, which can trigger clotting on surfaces. To prevent this, systemic anticoagulation is used, typically with heparin, and the level of anticoagulation is monitored with the activated clotting time (ACT). The goal is to maintain the ACT well above baseline so the blood remains liquid in the circuit under full CPB flow. The standard, widely used target is greater than 480 seconds. This level provides robust protection against circuit thrombosis while still allowing safe management of bleeding risk with protamine reversal at the end of bypass.

Targets around 420 seconds or 360 seconds would be considered insufficient for most CPB circuits and flow conditions, increasing the likelihood of clotting. A significantly higher target, like 600 seconds, would raise bleeding risk during and after surgery due to excessive anticoagulation. Therefore, keeping ACT above about 480 seconds is the best balance for typical CPB anticoagulation.