Low-Range Heparin and Protamine Detection: A Single-Center Prospective Diagnostic Study.

Area of Science:

• Anesthesiology and Critical Care Medicine
• Hematology
• Biomedical Engineering

Background:

• Accurate detection of low-range heparin activity is crucial for managing heparin reversal and rebound, particularly after cardiopulmonary bypass.
• Existing methods like anti-Xa activity (aXa), activated partial thromboplastin time (aPTT), kaolin-activated clotting time (kACT), and ROTEM viscoelastic tests have limitations in sensitivity, point-of-care availability, or cost.
• The Sonoclot viscoelastic test offers a potential alternative for monitoring heparin activity.

Purpose of the Study:

• To evaluate the performance of the Sonoclot slope-45 parameter for detecting low-dose heparin activity.
• To assess the impact of protamine, alone and in combination with heparin, on various coagulation parameters, including the Sonoclot slope-45.
• To compare the sensitivity of the Sonoclot slope-45 against established coagulation tests.

Main Methods:

• A prospective in vitro study was conducted using blood samples from 10 healthy volunteers.
• Blood samples were treated ex vivo with incremental low doses of heparin, protamine, or a combination of both.
• The effects on anti-Xa activity (aXa), activated partial thromboplastin time (aPTT), iSTAT kaolin-activated clotting time (kACT), ROTEM clotting time ratio, and the Sonoclot slope-45 were analyzed using receiver operating curve analysis.

Main Results:

• The Sonoclot slope-45, along with aXa and aPTT, reliably detected low heparin activity in spiked blood samples.
• The iSTAT kACT was found to be insensitive to low heparin concentrations.
• Protamine, whether administered alone or with heparin, did not significantly affect any of the tested coagulation parameters, including the Sonoclot slope-45.

Conclusions:

• The Sonoclot slope-45 demonstrates high sensitivity for detecting low-dose heparin activity.
• This sensitivity is maintained even in the presence of protamine, suggesting its utility in assessing heparin reversal.
• The Sonoclot slope-45 was found to be insensitive to protamine alone, further clarifying its specific role in heparin monitoring.