Cardiac Calculator

The Cardiac Calculator is an educational tool for healthcare professionals only to provide information on heparin and/or protamine effect on the Clotting Time (CT) results on the ClotPro.
It is NOT for therapeutic heparin monitoring.

In cardiac surgery, the most important information provided by IN-test is not the absolute CT value but the ratio between CT in IN-test and HI-test.


Here, a significant heparin effect can be assumed if CT HI-test/CT IN-test >1.25.


A prolongation of CT in IN-test AND HI-test can have several reasons:

  • Blood sampling within 5-10 min after protamine administration

  • Protamine overdose

  • Factor XII deficiency (not factor XIII) which is not associated with bleeding

  • Other deficiency of enzymatic factors of the intrinsic or common pathway (factor XI, IX, VIII, X, V, II, and I)

Only the latter one should be treated with plasma transfusion in case of clinically relevant bleeding. Therefore, these results have to interpreted with care and always in the clinical context (as stated in the intended and indications for use).

  1. If IN-test CT < 200 s, then NO Heparin or Protamine effect

  2. If IN-test CT AND HI-test CT > 260 s, then Protamine effect: Wait 20 mins, then repeat

  3. If IN-test CT > 200 s, then calculate ratio (IN-test CT / HI-test CT)

 Input IN-test CT >>>>> 
 Input HI-test CT >>>>> 
This calculator is intended for medical education only.  The user agrees that use is at their own risk.

1. Rapid disappearance of protamine in adults undergoing cardiac operation with cardiopulmonary bypass. Butterworth et al. Ann Thorac Surg 2002;74:1589-1595

2. Mochizuku T, Olsen P, Szlam F, Ramsay J & Levy J. Protamine reversal of Heparin Affects platelet aggregation and activated clotting time after cardiopulmonary bypass. Anaesthesia and analgesia. Vol 88 Issue 4 pp 781-785

3. Hoenicka M, Rupp P, Muller-Eising K, Deininger S, Kunert A, Liebold A, et al. Anticoagulation management during multivessel coronary artery bypass grafting: a randomized trial comparing individualized heparin management and conventional hemostasis management. J Thromb Haemost 2015;13:1196–206.

4. Can extra protamine eliminate heparin rebound following cardiopulmonary bypass surgery? Teoh et al. J Thorac Cardiovasc Surg 2004;128:211-219

5. Detection of Protamine and Heparin After Termination of Cardiopulmonary Bypass; Mittermayr M, Velik-Salchner C, Stalzer B, Margreiter J, Klingler A, Streif W, Fries D, Innerhofer P. Anesth Analg. 2009 Mar;108(3):743-50.

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