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Heparin-induced platelet dysfunction and cardiopulmonary bypass
E W Muriithi1, P R Belcher, S P Day
1Department of Cardiac Surgery, University of Glasgow, Royal Infirmary, Scotland. e.w.muriithi@clinmed.gla.ac.uk
The Annals of Thoracic Surgery
|July 13, 2000
Summary
Heparin in cardiopulmonary bypass indirectly inhibits platelet aggregation through plasma changes. This delayed effect is transferable to normal platelets in vitro, impacting blood clotting during surgery.
Area of Science:
- Cardiovascular Science
- Hematology
- Surgical Research
Background:
- Cardiopulmonary bypass (CPB) is linked to impaired platelet macroaggregation.
- Heparin administration before CPB can cause platelet dysfunction.
- In vitro heparinization of whole blood does not impair macroaggregation, suggesting an indirect mechanism.
Purpose of the Study:
- To investigate the mechanism of heparin-induced platelet dysfunction during CPB.
- To determine if plasma changes induced by in vivo heparinization affect platelet macroaggregation.
- To assess the delayed and transferable nature of this inhibition.
Main Methods:
- Whole blood impedance aggregometry was used to measure platelet macroaggregation in response to collagen.
- Blood samples were obtained from patients undergoing CPB and healthy volunteers.
- Platelet-poor plasma from CPB patients at various stages was used to dilute blood from volunteers and assess macroaggregation.
Main Results:
- Platelet-poor plasma obtained after heparinization or during CPB significantly reduced platelet macroaggregation compared to pre-heparinization.
- This inhibitory effect was transferable to normal platelets from volunteers.
- The inhibitory effect on macroaggregation in post-heparinization blood increased over time, showing a delayed onset.
Conclusions:
- In vivo heparinization induces plasma alterations that inhibit platelet macroaggregation.
- This inhibition is indirect, delayed, and can be transferred in vitro to normal platelets.
- Understanding these plasma-mediated effects is crucial for managing platelet function during CPB.