Protamine sulphate is used to reverse unfractionated heparin after cardiopulmonary bypass. The standard initial dose relationship is:

• A 10 mg protamine per 100 IU of heparin administered in the preceding hours
• B 1 mg protamine per 10 IU of heparin administered in the preceding hours
• C 1 mg protamine per 100 IU of heparin administered in the preceding hours ✓
• D Fixed 100 mg bolus regardless of heparin dose

Explanation

The accepted dosing is approximately 1 mg of protamine for every 100 IU of circulating heparin activity, titrated against activated clotting time after separation from bypass. Excess protamine is itself anticoagulant: it binds and inhibits thrombin, impairs platelet function and can paradoxically worsen bleeding, so empirical large fixed doses are avoided. The 1:10 and 10:100 relationships represent tenfold errors in either direction and are classic calculation traps in examination settings.

Reference: Miller's Anesthesia, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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