Table 2.

Comparison of UFH and bivalirudin.

Anticoagulant	Mechanism of action	Dosing range	Reversible	Monitoring tests	Limitations
UFH	Indirect – needs AT for maximal therapeutic effect	10–70 U/kg/h	Protamine sulfate	ACT, aPTT, anti-Xa, and TEG/ROTEM	• Only one-third of UFH molecules has pentasaccharide sequence that binds AT, which leads to variable anticoagulation • Does not inhibit clot-bound thrombin • Thrombocytopenia
Bivalirudin	Direct thrombin inhibitor	0.3–1.2 mg/kg/h	No specific antidote, but bleeding may be mitigated with factor VIIa	aPTT	• Expect INR will increase • Thrombosis with blood stasis (intracardiac and circuit)

UFH, unfractionated heparin; AT, antithrombin; TEG, thromboelastography; ROTEM, rotational thromboelastometry.