Heparin Sodium (Heparin Sodium)

Anesthesia Implications

Classification: Anticoagulant
Therapeutic Effects: Anticoagulant, and Antithrombotic.
Time to Onset: IV: Immediate

SC: 20–30 minutes
Time to Peak: IV: Immediate
SC: 2–4 hours
Duration: IV: 2–6 hours
SQ: 8–12 hours 

Contraindications

Severe thrombocytopenia or uncontrollable active bleeding.  Known sensitivity to heparin or heparin-induced thrombocytopenia (HIT).

Primary Considerations

Monitoring Coagulation – Ensure regular monitoring of activated partial thromboplastin time (APTT) or activated clotting time (ACT) to assess anticoagulation status. Maintain APTT at 1.5 to 2 times the control value for therapeutic anticoagulation.  ACT goals depend on the procedure.

Altered protein binding – Heparin can alter protein binding, creating a greater free-fraction of highly protein-bound drugs (ie. ceftriaxone, fentanyl, midazolam).

Bleeding Risks – Be cautious of increased bleeding risks, particularly in procedures with significant blood loss. Have emergency measures and reversal agents (e.g., protamine sulfate) ready for heparin reversal if excessive bleeding occurs.

Reversal Agent Protocol – Protamine sulfate is the antidote for heparin; administer 1 mg of protamine per 90–115 units of heparin to neutralize its effect. Prepare for potential side effects of protamine, including hypotension and anaphylactoid reactions.

Contraindications – Avoid using heparin in patients with uncontrolled active bleeding, severe thrombocytopenia, or heparin-induced thrombocytopenia (HIT). Known hypersensitivity to heparin or pork products.  

Platelet Count – Confirm platelet counts preoperatively to assess for thrombocytopenia and as a baseline to detect heparin-induced thrombocytopenia (HIT).

Neonates and Infants – Use preservative-free formulations of this drug in neonates and infants.

IV push dose

Use Actual Body Weight (ABW)

Percutaneous Stent Interventions

Initial Bolus Dose: 5,000–10,000 units or 60–100 U/kg.

Target ACT Goal: 300–350 seconds.

Rationale: Optimizes anticoagulation and minimizes thrombus formation during stent placement.

Open Vascular Surgeries (e.g., Carotid Endarterectomies):

Initial Bolus Dose: 100 U/kg.

Target ACT Goal: >200 seconds.

Rationale: Higher doses reduce the risk of cerebral ischemic events during procedures involving cross-clamping.

Peripheral Vascular Interventions:

Initial Bolus Dose: <60 U/kg.

Target ACT Goal: <250 seconds.

Rationale: Aimed at reducing bleeding complications and transfusion rates during interventions.

Reversal

Protamine sulfate (1 mg neutralizes 100 units of heparin) is the antidote, administered via slow IV infusion. Caution: may cause severe hypotension or anaphylactoid reactions.

Method of Action

Heparin acts by binding to antithrombin III, enhancing its activity to inhibit clotting factors (IXa, Xa, XIa, and XIIa). This prevents the conversion of prothrombin to thrombin, inhibiting the formation of a stable fibrin clot.

Metabolism

Primarily hepatic, with degradation into smaller fragments.

Elimination

Renal excretion of metabolized fragments.