Protamine Test Dose: Impact on Activated Clotting Time and Circuit Integrity

Background

Recurrent observation of clot in the cardiopulmonary bypass circuit following the administration of a Protamine Test Dose (PTD) prompted concern into the effects of PTDs on patient activated clotting times (ACT).

Methods

Data was prospectively collected on 120 cardiopulmonary bypass patients undergoing a variety of cardiac surgeries from July to October, 2018. ACTs were documented prior to cardiopulmonary bypass termination, post PTD, and post protamine full dose. Statistical analysis was completed using a paired t-test.

Results

The average PTD was calculated to be 36+21 mg or 11+7% of the full protamine dose of 367+153 mg. This “test” dose ranged from 1% to 67% of full dose depending upon the anesthetist. Post PTD ACTs were widely variable. On average, there was a 40+25% drop from last ACT on cardiopulmonary bypass (650+155 sec) to the ACT post PTD (376+153 sec) p<0.0001. In fact, 81+5% of the patient’s post PTD ACTs fell below our institutional ACT standard of 480 seconds for safe cardiopulmonary bypass initiation.

Conclusions

Regardless of the protamine test dosage, there is no reliable way to predict how a patient’s ACT will respond to a protamine test dose. Clot formation and circuit integrity is at risk when pump suction devices are continuously in use during PTD administration. Therefore, we strongly recommend that the direct recovery of mediastinal shed blood into the pump circuit be discontinued before any amount of protamine is administered to the patient.