Overview

Open-heart surgery requires temporarily stopping the heart and lungs and diverting the patient's blood to an outside system that takes over the function of the heart and lungs. This is possible through the use of cardiopulmonary bypass (CPB) which diverts blood, through plastic tubing, to a heart-lung machine which includes an oxygenator. The external oxygenator works as an artificial lung. This allows cardiac surgeons to operate in a field that is free of blood, while the patient's body continues to receive healthy blood.

CPB is an advanced medical technology that allows for heart surgeries, such as coronary artery bypass, heart valve surgery, and procedures involving major blood vessels. It is recognized that there are many risks associated with its use, including microscopic stress exerted on blood components by the oxygenator and tubing, which can lead to irreversible damage to the blood cells. This effect can contribute to bleeding during and after surgery. This type of bleeding can be difficult to monitor and treat, especially given the limited access to point-of-care blood testing to inform clinicians on what part of the blood is failing to function properly.

The investigators will use a point-of-care machine called Plateletworks to test the function of platelets during surgeries which require CPB. Platelets are an important part of blood that help stop bleeding by forming clots. At the investigators' institution two oxygenators are currently used interchangeably. These oxygenators have different properties that may impact how platelets function. This project will help determine if using a higher pressure oxygenator increases the risk of patients bleeding. Additionally, the investigators will compare the platelet data from Plateletworks to data collected from rotational thromboelastometry (ROTEM). This will yield valuable data about commonly used oxygenators and tests which can ultimately improve patient care.

Eligibility

Inclusion Criteria:

• Scheduled for non emergent cardiac surgery
• Anticipated long CPB time (Multi-vessel CABG, multi-valve surgeries, or combined CABG and valve procedures)

Exclusion Criteria:

• Pregnancy
• Age under 18 years on the surgery date
• Weight less than 60kg
• Any known pre-existing bleeding disorder
• Inability to provide informed consent
• Pre-existing abnormal fibrinogen level (normal: 1.8-4.7g/l)
• Significant liver disease (alanine aminotransferase or aspartate aminotransferase > 150 U/l)
• INR > 1.4
• PTT greater than 38 (off IV heparin for 12h prior to testing)
• Direct oral anticoagulant (DOAC) use within 72h preoperatively
• Significant renal disease (eGFR < 50)
• Emergency surgery
• Intake of anti-platelet drugs (including ticagrelor and Plavix but excluding ASA) within three days (72h) preoperatively
• Anemia (Hb < 110)
• Deep vein thrombosis (DVT) (within 3 months prior to OR)
• Pulmonary embolism (within 3 months prior to OR)
• Stroke (within 3 months prior to OR)
• Planned hypothermia below 28 degrees Celsius.