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Clinical References

Pharmacology

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Learning Center/Pharmacology/Heparin (Unfractionated)

anticoagulant

Heparin (Unfractionated)

Heparin sodium

Route: IV · Subcutaneous
Onset: IV immediate; SC 20–60 minutes
Duration: Half-life about 60–90 minutes

Mechanism of action

Binds antithrombin and greatly accelerates its inactivation of thrombin (IIa) and factor Xa. Short half-life and fully reversible with protamine.

Dosing

Adult: VTE treatment: 80 units/kg IV bolus, then 18 units/kg/h, titrated to aPTT or anti-Xa. Prophylaxis: 5,000 units SC every 8–12 hours
Pediatric: Weight-based bolus and infusion per institutional nomogram

Reversal: protamine about 1 mg per 100 units of heparin given in the previous 2–3 hours (max 50 mg).

Indications

Treatment of pulmonary embolism and deep vein thrombosis, especially when thrombolysis, procedures or severe renal impairment are possible
VTE prophylaxis
Acute coronary syndromes, ECMO and dialysis circuits
Anticoagulant in arterial blood gas syringes (dry, lyophilized heparin)

Contraindications

Active major bleeding
History of heparin-induced thrombocytopenia (HIT)
Severe thrombocytopenia

Side effects

Bleeding
Heparin-induced thrombocytopenia (paradoxical thrombosis)
Osteoporosis with long-term use
Hyperkalemia (aldosterone suppression)

Monitoring parameters

aPTT or anti-Xa level
Platelet count (HIT, typically days 5–10)
Hemoglobin and signs of bleeding

Drug interactions

Increased bleeding with antiplatelets, thrombolytics, other anticoagulants

NBRC high-yield

Antithrombin-mediated anticoagulant; monitor aPTT/anti-Xa and platelets
Protamine reverses
Too much liquid heparin in an ABG syringe lowers PaCO2

Clinical pearls

ABG pearl: excess liquid heparin in a syringe dilutes the sample and falsely lowers PaCO2 and HCO3 — use pre-heparinized dry syringes
Preferred over LMWH when a procedure, thrombolysis or rapid reversal may be needed

Heparin (Unfractionated) (Heparin sodium) — Respiratory Pharmacology