heparin/protamine

Question 1

72 year old undergoing CABG about to go on bypass. heparin has been administered but ACT remains low. what do you think?

Answer 1

• wrong medication
• insufficient dose of heparin
• IV infiltration
• inaccurate ACT machine
• heparin resistance (antithrombin III deficiency from inherited defect of production, excessive loss - nephrotic syndrome, excessive consumption - sepsis/trauma)

Question 2

assume it is antithrombin III deficiency, what is the treatment and why?

Answer 2

FFP.
Antithrombin III is a serine protease that contributes to anticoagulation by irreversibly binding to thrombin and factors X, XI, XII, XIII. heparin complexes with antithrombin III and enhances its activity 1000 fold. heparin alone cannot produce anticoagulation.

Question 3

after coming off bypass, patient is given protamine for heparin reversal at a 1:1 ration. suddenly the pressure drops to 61/28 mmHg and the PA pressure increases. what is happening?

Answer 3

protamine-induced histamine release may lead to increased PVR and decreased SVR.

on the other hand, the increased PAP may be the result of a type III protamine reaction. protamine-heparin complex-induced release of thromboxane A2 leads to increased PAP with subsequent RH failure. it could also be LV dysfxn.

Question 4

what steps can you take to prevent a type III protamine reaction?

Answer 4

there is no reliable way to prevent this type of reaction, but diluting the protamine and administering it slowly sees a reasonable approach

Question 5

would you infuse protamine via PAC or directly into the bypass circuit?

Answer 5

i would not administer it into the PAC since it could cause pulmonary HTN, nor would i administer it directly into the bypass machine because it could result in clot formation. the route of administration, central vs. peripheral does not seem to make a difference. however, there may be some evidence that ASA one week prior to CPB may be beneficial.