Heparin & Protamine Calculator for Adult CPB
Plan an initial UFH bolus using weight strategy, then estimate post-CPB protamine reversal using total UFH, initial bolus, or a custom UFH reference.
Adult CPB only. Not intended for pediatric CPB, ECMO maintenance anticoagulation, ICU heparin infusion, dialysis anticoagulation, or VTE treatment protocols.
Use this page to estimate and reference anticoagulation workflow support. Follow institutional protocol for all dosing decisions.
Adult CPB workflow
Use Section 1 before bypass to estimate the initial UFH plan, Section 2 during CPB if ACT response is unexpectedly low or heparin resistance is suspected, and Section 3 after bypass to estimate protamine from the selected heparin exposure basis.
1. Pre-CPB: Initial UFH Plan
How much initial heparin should I plan based on this patient and weight strategy?
Patient and dosing inputs
Adult CPBDevine IBW: Male = 50 + 0.91 × (cm − 152.4), Female = 45.5 + 0.91 × (cm − 152.4).
ABW 0.4 / 0.3 rules: ABW = IBW + factor × (TBW − IBW); factor 0.4 when BMI 30–39, factor 0.3 when BMI ≥ 40.
Auto logic: BMI < 30 → TBW; BMI 30–39 → ABW (0.4); BMI ≥ 40 → ABW (0.3).
Initial dose (U/kg)
Initial UFH plan
Enter patient parameters to calculate
Height and weight are required before results appear.
Sensitivity at selected initial dose
How would the estimated initial UFH bolus change with other weight strategies at the current U/kg dose?
TBW
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ABW
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IBW
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2. During CPB: Additional UFH & Heparin Resistance Cue
During CPB, additional UFH may be given according to institutional protocol when ACT is below target. Some protocols use incremental boluses such as 50–100 U/kg, but fixed redosing is not universal. If ACT does not increase as expected, use this checklist to consider heparin resistance contributors.
› Heparin Resistance Cue Checklist Non-validated reminder tool · click to expand
Low heparin resistance cue. Continue institutional ACT/heparin monitoring.
Non-validated screening aid. This checklist is a reminder tool, not a diagnostic score or medication-order protocol.
3. Post-CPB: Protamine Reversal
Given the planned or actual heparin exposure and selected protamine strategy, what is the estimated protamine dose?
Selected heparin plan
Enter patient data above to populate the initial UFH plan.
Protamine inputs
A. Heparin exposure during case
Auto-fills from Section 1 when available; edit if the actual dose differs.
B. Protamine calculation basis
Uses total entered UFH exposure as the protamine reference. Simple and common, but may overestimate reversal needs when CPB duration is long.
C. Protamine-to-heparin ratio
Protamine estimate
Estimated protamine dose
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Warning: protamine ratio above 1.0 may increase bleeding/coagulopathy risk.
Warning: calculated protamine dose is unusually high. Reassess the UFH reference amount and workflow context.
Protamine dosing may be estimated from total UFH, initial systemic UFH bolus, measured heparin concentration, or local protocol. Use institutional protocol and clinical assessment.
Clinical safety notes
Heparin resistance cue
High cumulative UFH exposure. If ACT remains below institutional target or <480 sec despite ≥500 U/kg UFH, consider heparin resistance evaluation.
- Confirm full heparin delivery.
- Confirm sample quality and ACT device validity.
- Recheck ACT after 3–5 minutes.
- Consider AT activity, heparin concentration, or anti-Xa if available.
- Consider AT concentrate or FFP per institutional protocol.
- HIT/suspected HIT: do not use routine UFH workflow.
Protamine safety notes
- Protamine overdose can worsen coagulopathy.
- Time-based heparin decay during CPB is variable.
- Include circuit prime heparin only when it is expected to enter the patient/systemic circulation according to local workflow.
Methodology, FAQ, references
Methodology notes
- Initial UFH bolus = selected dosing weight × selected U/kg preset.
- Auto weight strategy uses TBW when BMI <30, ABW 0.4 when BMI 30–39, and ABW 0.3 when BMI ≥40.
- Protamine estimate = UFH reference amount ÷ 100 × selected protamine-to-heparin ratio.
- Total UFH basis includes initial systemic UFH, additional systemic UFH during CPB, and circuit prime heparin when entered.
- Initial-bolus basis uses only the initial systemic UFH amount, while custom basis uses the entered custom UFH reference.
- ACT targets vary by institution, circuit, and device. This calculator does not use ACT target to calculate UFH or protamine dose. Confirm anticoagulation using local ACT/heparin monitoring protocol.
- Major CPB guidelines emphasize ACT/heparin monitoring and institutional protocols rather than a universal fixed UFH redosing dose. A 2024 ISTH SSC communication proposed inability to reach ACT ≥480 sec after 500 U/kg UFH as a standardized adult cardiac surgery definition of heparin resistance.
FAQ
How is initial heparin dose calculated for adult CPB?
Initial UFH bolus is commonly estimated from a selected dosing weight multiplied by a dose such as 250–400 U/kg, depending on institutional protocol. This calculator supports TBW, IBW, adjusted body weight, and auto-detect weight strategy to help compare initial adult CPB dosing estimates.
Which weight strategy should be used for obese patients?
There is no single universal strategy for all institutions. This calculator’s auto mode uses TBW when BMI is <30, ABW 0.4 when BMI is 30–39, and ABW 0.3 when BMI is ≥40. The sensitivity comparison shows how TBW, ABW, and IBW change the estimated initial UFH dose.
How is protamine dose estimated after CPB?
Protamine dose may be estimated using a selected UFH reference amount and a protamine-to-heparin ratio. This page supports total UFH administered, initial systemic UFH bolus, or a custom UFH reference basis. The displayed dose is an estimate and should be interpreted with institutional protocol and clinical assessment.
What is the difference between total UFH and initial-bolus protamine basis?
Total UFH basis includes entered heparin exposure such as initial UFH, additional UFH during CPB, and circuit prime heparin when included. Initial-bolus basis uses only the first systemic patient bolus as the reference amount. Total-dose methods are simple but may overestimate reversal needs when CPB duration is long; initial-bolus methods may reduce protamine exposure but may underestimate reversal needs after additional UFH.
Why can protamine overdose worsen bleeding?
Protamine is needed to reverse heparin, but excess protamine can impair coagulation and platelet function and may contribute to hypotension or other adverse reactions. Avoid interpreting the estimate as an automatic medication order; evaluate residual heparin, surgical bleeding, platelets, fibrinogen, temperature, calcium, and local protocol.
When should heparin resistance be suspected?
Heparin resistance should be considered when adequate ACT is not achieved despite high-dose UFH exposure, after confirming heparin delivery, sample quality, and ACT device validity. ACT targets are monitoring references, not dosing inputs in this calculator. A 2024 ISTH SSC communication proposed inability to reach ACT ≥480 seconds after 500 U/kg UFH as a standardized adult cardiac surgery definition.
Is this calculator for ECMO or ICU heparin infusion?
No. This calculator is for adult CPB heparin planning and post-CPB protamine estimation. It is not intended for ECMO maintenance anticoagulation, ICU heparin infusion, dialysis anticoagulation, VTE treatment, or pediatric CPB protocols.
Selected references
- Shore-Lesserson L, et al. STS/SCA/AmSECT Clinical Practice Guidelines: Anticoagulation during Cardiopulmonary Bypass. Ann Thorac Surg / J Extra Corpor Technol. 2018.
- Wahba A, et al. 2024 EACTS/EACTAIC/EBCP Guidelines on cardiopulmonary bypass in adult cardiac surgery. Eur J Cardiothorac Surg / Interdiscip Cardiovasc Thorac Surg. 2025.
- Vienne M, et al. Adjusted calculation model of heparin management during cardiopulmonary bypass in obese patients. Eur J Anaesthesiol. 2018.
- Levy JH, Sniecinski RM, Maier CL, Despotis G, Ghadimi K, Helms J, Ranucci M, Steiner ME, Tanaka KA, Connors JM. Finding a common definition of heparin resistance in adult cardiac surgery: Communication from the ISTH SSC Subcommittee on Perioperative and Critical Care Thrombosis and Hemostasis. J Thromb Haemost. 2024.