Heparin Dosing for Aortic Cross-Clamping
For aortic cross-clamping procedures, administer unfractionated heparin at 100 U/kg intravenous bolus, targeting an activated clotting time (ACT) of 200-250 seconds. 1
Weight-Based Dosing Strategy
Administer 100 U/kg as an initial intravenous bolus before applying the aortic cross-clamp, as this achieves adequate anticoagulation (ACT ≥200 seconds) in approximately 78% of patients within 5 minutes. 1
For cardiovascular surgery involving total body perfusion, the FDA-approved dosing is higher: not less than 150 U/kg, with 300 U/kg for procedures under 60 minutes and 400 U/kg for procedures exceeding 60 minutes. 2 However, these cardiac surgery protocols are inappropriate and dangerous for non-cardiac vascular procedures like standard aortic cross-clamping. 3
Weight-based dosing is superior to fixed-dose regimens (such as 5,000 U boluses), which result in inadequate anticoagulation in the majority of patients and significant delays in achieving therapeutic levels. 1, 4
Target ACT and Monitoring
Target ACT range is 200-250 seconds for non-cardiac arterial procedures without glycoprotein IIb/IIIa inhibitors. 5, 3, 1
Measure ACT 5 minutes after the initial heparin bolus to guide additional dosing. 1
If ACT remains below 200 seconds after the initial dose, administer additional heparin according to a protocol-driven approach: approximately 91% of patients achieve target ACT after one additional dose. 1
Avoid ACT values exceeding 300 seconds, as this increases bleeding risk without additional thrombotic protection. 5, 1
Special Populations
Obese Patients
In morbidly obese patients, consider using an adjusted dosing weight rather than actual body weight to prevent excessive delays in achieving therapeutic anticoagulation. 4
Recommended formulas include: dosing weight = ideal body weight (IBW) + 0.3(actual body weight - IBW) or dosing weight = IBW + 0.4(actual body weight - IBW). 4
Paradoxically, obese patients may require lower weight-adjusted doses (U/kg) to achieve target ACT, as body mass index inversely correlates with heparin dose requirements. 6
Critical Pitfalls to Avoid
Never use cardiac surgery dosing protocols (targeting ACT >325 seconds) for peripheral vascular or aortic procedures, as these are excessive and increase bleeding complications. 5, 3
Avoid fixed-dose heparin boluses (e.g., 5,000 U) without weight adjustment, as these fail to achieve adequate anticoagulation in most patients. 3, 1
Do not rely on ACT monitoring alone without initial weight-based dosing, as this delays therapeutic anticoagulation. 1
Limit anticoagulation duration to the intraoperative and immediate postoperative phase only to minimize bleeding risk. 3