How do I reverse unfractionated heparin in a patient with a major bleed?

By William Aird

For IV heparin:

  • Protamine sulfate dosing is 1 mg per 100 units of heparin, if heparin was given in the previous 2-3 hours.
  • Protamine sulfate is given slower than 5 mg/minute to minimize the risk of adverse reactions.
  • Maximum dose of protamine sulfate is 50 mg.

For SC heparin:

  • When heparin has been given subcutaneously (and therefore is cleared with a longer half-life) prolonged or repeated administration of protamine sulfate may be required.

See protamine reversal calculator.