Extracorporeal circulation in sheep with normal bleeding time using a surface heparinized circuit.

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Hematology

Background:

• Systemic heparinization during extracorporeal respiratory support (ERS) poses a significant bleeding risk.
• Developing strategies to minimize anticoagulation while maintaining circuit patency is crucial for ERS safety.

Purpose of the Study:

• To evaluate the feasibility of prolonged venovenous bypass using a heparin-coated circuit at low systemic heparin levels.
• To assess the impact of reduced heparinization on coagulation parameters and bleeding times in an animal model.

Main Methods:

• An animal study involving eight sheep undergoing venovenous bypass with a heparin-coated circuit (Carmeda Biological Active Surface).
• A protocol included periods of high and low heparin dosing, with activated coagulation time (ACT) monitoring.
• Bleeding times, antithrombin III (AT III) levels, and thrombin coagulase time (TC) were measured.

Main Results:

• The heparin-coated system allowed for 24-hour bypass with normal coagulation times during low heparin dose periods (3-8 U/kg/hr).
• Bleeding time significantly decreased when transitioning from high to low heparin levels (27.9 min vs. 10.2 min).
• Maintaining AT III above 70% correlated with minimal changes in TC, indicating stable fibrinolysis.

Conclusions:

• Heparin-coated circuits facilitate prolonged extracorporeal perfusion with significantly reduced systemic heparin requirements.
• This approach offers a potential strategy to mitigate bleeding complications associated with ERS.
• The study demonstrates the safety and efficacy of using bioactive heparin surfaces for advanced respiratory support.