Heparin Reversal in an 87-Year-Old Patient with Port-a-Cath
Administer protamine sulfate at 1 mg for every 100 units of heparin given in the previous 2-3 hours (maximum 50 mg per dose), delivered slowly over 10 minutes by IV infusion. 1, 2, 3
Immediate Dosing Algorithm
Calculate the protamine dose based only on heparin administered in the preceding 2-3 hours, NOT the total cumulative dose. 1, 2
Time-Based Dose Adjustments:
- < 30 minutes since last heparin: Full dose at 1 mg protamine per 100 units heparin 1, 2
- 30-60 minutes ago: Reduce to 0.5-0.75 mg per 100 units 1, 2
- 60-120 minutes ago: Reduce to 0.375-0.5 mg per 100 units 1, 2
- > 120 minutes ago: Protamine likely not needed, as heparin has a half-life of approximately 30 minutes IV 1, 3
Critical Administration Protocol
Infuse protamine slowly over a minimum of 10 minutes to prevent potentially fatal cardiovascular collapse, severe hypotension, bradycardia, and anaphylactoid reactions. 1, 2, 3 Rapid administration (>5 mg/min) markedly increases the risk of life-threatening hemodynamic events. 1
High-Risk Patient Considerations:
The 87-year-old patient may have increased sensitivity to protamine's adverse effects. 1 Patients with fish allergies, previous protamine exposure, or use of protamine-containing insulin are at particularly high risk for severe anaphylactoid reactions. 4
Post-Reversal Monitoring
Measure aPTT or ACT 5-10 minutes after protamine administration to confirm adequate reversal. 1, 2 If the aPTT/ACT remains elevated, administer additional protamine at 0.5 mg per 100 units of the original heparin dose. 1, 2
Port-a-Cath Specific Considerations
The presence of a port-a-cath does not alter the protamine dosing strategy. 1, 2 However, ensure resuscitation equipment and treatment for anaphylactoid shock are immediately available before administering protamine, as fatal reactions can occur. 3
Common Pitfalls to Avoid
- Do NOT calculate protamine based on total cumulative heparin dose – this leads to protamine overdosing and increased risk of adverse effects, as protamine itself has intrinsic anticoagulant properties at high doses. 5, 1, 2
- Do NOT exceed 50 mg protamine in a single 10-minute administration – this is the maximum safe dose per infusion. 1, 2, 3
- Do NOT administer protamine rapidly – infusion faster than 5 mg/min significantly increases the risk of severe hypotension and anaphylaxis. 1
- Do NOT routinely reverse prophylactic subcutaneous heparin unless aPTT is significantly prolonged or active bleeding is present. 1
If Low Molecular Weight Heparin Was Used Instead
If the patient received enoxaparin (LMWH) rather than unfractionated heparin within 8 hours, administer 1 mg protamine per 1 mg enoxaparin (maximum 50 mg). 1, 4 However, protamine only achieves approximately 60% neutralization of LMWH's anti-Xa activity, so reversal will be incomplete. 1, 4