Activated Clotting Time during Cardiopulmonary Bypass: Is Repetition Necessary during Open Heart Surgery?

Finding a common definition of heparin resistance in adult cardiac surgery: communication from the ISTH SSC subcommittee on perioperative and critical care thrombosis and hemostasis

Ensuring adequate anticoagulation for patients requiring cardiac surgery and cardiopulmonary bypass (CPB) is important due to the adverse consequences of inadequate anticoagulation with respect to bleeding and thrombosis. When target anticoagulation is not achieved with typical doses, the term heparin resistance is routinely used despite the lack of uniform diagnostic criteria. Prior reports and guidance documents that define heparin resistance in patients requiring CPB and guidance documents remain variable based on the lack of standardized criteria. As a result, we conducted a review of clinical trials and reports to evaluate the various heparin resistance definitions employed in this clinical setting and to identify potential standards for future clinical trials and clinical management. In addition, we also aimed to characterize the differences in the reported incidence of heparin resistance in the adult cardiac surgical literature based on the variability of both target-activated clotting (ACT) values and unfractionated heparin doses. Our findings suggest that the most extensively reported ACT target for CPB is 480 seconds or higher. Although most publications define heparin resistance as a failure to achieve this target after a weight-based dose of either 400 U/kg or 500 U/kg of heparin, a standardized definition would be useful to guide future clinical trials and help improve clinical management. We propose the inability to obtain an ACT target for CPB of 480 seconds or more after 500 U/kg as a standardized definition for heparin resistance in this setting.

Heparin Resistance During Cardiopulmonary Bypass in Adult Cardiac Surgery

The use of heparin for anticoagulation has changed the face of cardiac surgery by allowing a bloodless and motionless surgical field throughout the introduction of cardiopulmonary bypass (CPB). However, heparin is a drug with complex pharmacologic properties that can cause significant interpatient differences in terms of responsiveness. Heparin resistance during CPB is a weighty issue due to the catastrophic consequences stemming from inadequate anticoagulation, and the treatment of it necessitates a rationalized stepwise approach due to the multifactorial contributions toward this entity. The widespread use of activated clotting time (ACT) as a measurement of anticoagulation during CPB is examined, as it may be a false indicator of heparin resistance. Heparin resistance also has been repeatedly reported in patients infected with COVID-19, which deserves further exploration in this pandemic era. This review aims to examine the variability in heparin potency, underlying mechanisms, and limitations of using ACT for monitoring, as well as provide a framework towards the current management of heparin resistance.

Surface Modification of Polypropylene Blood Oxygenator Membrane by Poly Ethylene Glycol Grafting

Blood oxygenators play key role in Extra Corporeal Membrane Oxygenator (ECMO) system using for patients with acute respiratory problems, immature fetal and also in open heart surgery. Interaction between blood and blood oxygenator polymeric membrane surface lead to fouling phenomena which have negative effect on performance of this important medical device. A modification comprising surface activation, PEG immersing and PEG graft polymerization carried out to provide acceptable blood oxygenator performance, blood compatibility and reduction in heparin consumption at the same time. Modified membranes characterized by FTIR, contact angle measurements and Atomic Force Microscopy (AFM) analyses. Blood compatibility of modified surface was also detected by SEM images. Results clearly indicate that modifying membranes by PEG is an effective way for anti-fouling properties. Water contact angel reduction from 110ْ to 72ْ shows hydrophilicity enhancement, roughness increasing from 15 to 20 and blood compatibility improvement was investigated by SEM and AFM analysis results respectively.