Antithrombin as a Predictor of Heparin Resistance in Cardiac Surgery With Cardiopulmonary Bypass

This study aims to investigate whether the level of antithrombin (AT) in the blood before cardiac surgery can predict how well patients respond to heparin, a medication used to prevent blood clotting during surgery with a heart-lung machine (cardiopulmonary bypass). Heparin requires antithrombin to work effectively. Some patients have lower levels of antithrombin, which may result in reduced response to heparin, a condition known as heparin resistance. This can lead to difficulties achieving adequate anticoagulation during surgery and may require additional medication or adjustments in treatment. In this study, an additional blood sample will be taken after anesthesia induction but before the administration of heparin. No changes will be made to the patient's treatment or care. Clinical data, including laboratory values, heparin dosing, and surgical outcomes, will be collected from routine medical records. The goal is to identify a clinically useful antithrombin threshold that can help detect patients at risk of heparin resistance. This may improve patient safety, optimize treatment strategies, and reduce unnecessary use of antithrombin therapy in the future.

This is a prospective observational cohort study conducted at Sahlgrenska University Hospital, Sweden, aiming to evaluate whether preoperative antithrombin (AT) levels can predict heparin resistance in adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Background: Heparin is routinely administered during CPB to prevent clot formation in the extracorporeal circuit. Its anticoagulant effect depends on the presence of antithrombin, a natural inhibitor of coagulation. Reduced antithrombin levels are a known cause of impaired heparin response. However, clinically relevant threshold values for when antithrombin supplementation should be considered are not well established. Heparin resistance may lead to delayed procedures, repeated heparin dosing, insufficient anticoagulation, and increased resource utilization. Identifying patients at risk prior to heparin administration could allow for more structured and efficient management. Study Design: This is a non-interventional, prospective observational study. All patients will be treated according to standard clinical practice. No randomization or protocol-driven intervention will be performed. A preoperative antithrombin level will be measured in a standardized manner after induction of anesthesia and prior to heparin administration and significant fluid administration. The timing is chosen to minimize the influence of circadian variation, anesthesia, and hemodilution. Study Population: Adult patients (≥18 years) scheduled for elective or sub-acute cardiac surgery requiring cardiopulmonary bypass will be consecutively included. Inclusion criteria: Age ≥18 years Planned cardiac surgery with cardiopulmonary bypass Exclusion criteria: Emergency surgery Ongoing antithrombin supplementation prior to surgery Known severe congenital coagulation disorders Severe liver failure Missing key data required to define heparin resistance Data Collection: In addition to the antithrombin measurement, clinical data will be collected from medical records, anesthesia charts, perfusion protocols, and laboratory systems. Data include: Demographics and medical history Comorbidities and medication exposure (especially heparin/LMWH) Laboratory variables Surgical and perioperative variables Heparin dosing and activated clotting time (ACT) measurements Need for additional heparin or antithrombin Postoperative outcomes, including bleeding, transfusions, reoperation, and ICU stay Outcome Measures: Primary outcome: Heparin resistance, defined as failure to achieve an activated clotting time (ACT) ≥480 seconds after an initial heparin dose of 350 IU/kg according to standard clinical practice. Secondary outcomes: ACT after initial heparin dose Total heparin dose required to reach target ACT Need for antithrombin supplementation Bleeding and transfusion requirements Operative time, CPB duration, and aortic cross-clamp time ICU length of stay and early postoperative complications Statistical An Покажи пълното описание...

Inclusion Criteria: * Age ≥18 years * Planned cardiac surgery with cardiopulmonary bypass * Ability to provide informed consent Exclusion Criteria: * Emergency cardiac surgery * Ongoing antithrombin supplementation prior to surgery * Known severe congenital coagulation disorder affecting interpretation of outcomes * Severe liver failure * Missing key data required to define heparin resistance (e.g., missing heparin dose or ACT values)