← Coagulation Related
Heparin (unfractionated)
Indirect thrombin inhibitor
Activates antithrombin → inactivates IIa (thrombin) and Xa.
Indications
- •Cardiopulmonary bypass
- •Vascular surgery
- •DVT/PE treatment
- •ACS
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| CPB | 300–400 U/kg, target ACT ≥ 480 sec | — |
| DVT/PE | 80 U/kg bolus + 18 U/kg/hr, titrate to aPTT 1.5–2.5× | — |
| Vascular cross-clamp | 5,000 U IV before clamp | — |
Pharmacokinetics
Onset immediate IV. Half-life 1–2 h (dose-dependent).
Side effects
- !Bleeding
- !HIT (heparin-induced thrombocytopenia) types I and II
- !Hyperkalemia (aldosterone suppression with prolonged use)
- !Osteoporosis with chronic use
Contraindications
- ×Active major bleeding
- ×HIT history (use bivalirudin/argatroban)
Reversal / antidote
Protamine 1 mg per 100 U heparin (max 50 mg per dose). Slow push to avoid hypotension + pulmonary HTN.
Clinical pearls
- ★ACT measures heparin effect during CPB; aPTT for treatment dose.
- ★Resistance possible with antithrombin deficiency or sepsis — give AT-III concentrate or FFP.
- ★Protamine reactions: hypotension, pulmonary HTN, anaphylaxis (especially in NPH-insulin patients).
Other drugs in Coagulation Related
- Tranexamic Acid (TXA)
Reversibly binds plasminogen, blocking conversion to plasmin → preserves fibrin clot.
- Protamine Sulfate
Strongly basic (positive-charge) protein binds to highly acidic (negative-charge) heparin → inactive ionic complex → renal excretion. 1 mg protamine neutralizes ~100 units heparin.
- DDAVP (Desmopressin)
Selective V2 agonist (renal water retention + Factor VIII/vWF release from endothelial Weibel-Palade bodies). NO V1 vasopressor activity at therapeutic dose.
Browse all classes: /reference/drugs
Education only — confirm against current package inserts and institutional protocols. Doses assume normal organ function unless otherwise noted.
