Heparin Dosing for Aortic Cross-Clamping in a 75 kg Patient
For a 75 kg patient undergoing aortic cross-clamping in non-cardiac vascular surgery, administer 7,500 units (100 U/kg) of unfractionated heparin as an intravenous bolus, targeting an activated clotting time (ACT) of 200-250 seconds. 1
Weight-Based Dosing Strategy
The standard dose is 100 U/kg for non-cardiac arterial procedures involving aortic cross-clamping. 1, 2 This translates to 7,500 units for a 75 kg patient.
Cardiac surgery protocols using ≥150 U/kg (up to 400 U/kg) are inappropriate and hazardous for non-cardiac vascular procedures, as they significantly increase bleeding risk without additional thrombotic protection. 1, 3
Fixed-dose boluses (e.g., 5,000 units) without weight adjustment fail to achieve adequate anticoagulation in the majority of patients and must be avoided. 1, 2
Target ACT and Monitoring
Maintain ACT between 200-250 seconds for non-cardiac arterial procedures. 1
Measure ACT 5 minutes after the initial heparin bolus to guide additional dosing. 2
After an initial dose of 100 U/kg, approximately 78% of patients achieve an ACT ≥200 seconds, while 46% reach ≥250 seconds. 2
ACT values exceeding 300 seconds must be avoided as they increase bleeding complications without providing additional benefit. 1
Additional Dosing Protocol
If the initial ACT is <200 seconds, administer additional heparin in increments guided by ACT measurements. 2
Approximately 51% of patients require at least one additional heparin dose to achieve target ACT. 2
After one additional dose, 91% of patients reach an ACT ≥200 seconds. 2
Critical Pitfalls to Avoid
Never apply cardiac surgery heparin protocols (targeting ACT >325 seconds) to peripheral vascular or aortic procedures, as this leads to excessive bleeding without improving outcomes. 1, 4
Do not use the high-dose regimens recommended for total body perfusion (150-400 U/kg), which are FDA-approved only for open-heart surgery with cardiopulmonary bypass. 3, 1
Weight-based dosing using actual body weight is essential; however, in morbidly obese patients (>150 kg), lower weight-adjusted doses (U/kg) may be required to avoid supratherapeutic anticoagulation. 5, 6
Post-Procedure Management
Routine post-procedural heparin infusions are not recommended after uncomplicated vascular procedures, as they increase bleeding events. 1, 4
Limit anticoagulation to the intra-operative period and immediate post-operative phase only. 1
If continued anticoagulation is clinically necessary (e.g., residual thrombus, significant dissection), subcutaneous heparin is safer than intravenous infusion. 1, 4