Heparin Dose and Post Operative Bleeding in Cardiopulmonary Bypass Patients
Condition: Coronary Artery Disease
MeSH terms: Coronary Artery Disease; Postoperative Hemorrhage
Study type: Observational

Summary: 
      Blood is anticoagulated using a drug named heparin during open-heart surgery to allow it to
      safely pass through the heart-lung machine which pumps the blood throughout the body during
      the surgery. Each patient is given the heparin they need for their surgery. This means some
      patients receive more or less heparin than other patients. In this study, the investigators
      will be evaluating the current anticoagulation protocol for open heart surgery in use at the
      Royal University Hospital. The goal of this project is to compare patients who require and
      receive more heparin for proper anticoagulation to those patients who require and receive
      less heparin.

      Open-heart surgery will proceed according to the standard hospital protocol. All research
      participants will be treated according to standard post-open heart surgery protocol in the
      ICU. This will include measurement of blood loss by keeping track of chest tube outputs and
      administration of blood transfusions.

      This study focuses on Saskatoon Health Region patients having open heart surgery in terms of
      the protocol for anticoagulation and blood transfusions.
    

Detailed description: 
      This study examines heparin doses of patients having cardiopulmonary bypass supported surgery
      in terms of their sensitivity and resistance to heparin which is the standard anticoagulant
      used. The investigators use the Heparin Management System, an analyser that performs a
      heparin dose response test. In this test, a patient's whole blood is mixed with increasing
      amounts of heparin to determine the required dose to achieve a set level of anticoagulation.
      Patients who are found to resistant to heparin and needing a higher dose are thought by some
      to bleed more post operatively. It is my view that when the patient is given the correct
      amount of heparin which is then reversed by the correct amount of protamine (the reversal
      agent) the bleeding is not determined by heparin dose.

      Hypothesis statement: Higher doses of heparin do not cause increased postoperative bleeding
      and transfusion events in the postoperative CPB patient.

      Purposes of the Study

        1. Compare heparin sensitive and resistant patients in terms of postoperative bleeding and
           transfusion events.

        2. Determine the incidence of heparin sensitivity or resistance in patients.

        3. Identify preoperative factors that lead to heparin resistance or sensitivity in
           patients.

        4. Using the Heparin Dose Response test in determining heparin resistant and sensitive
           patients.

        5. Examination of anticoagulation protocol for open-heart surgery.

        6. Effect of preoperative antiplatelet and anticoagulant therapy on perioperative care.

        7. Use routine laboratory tests and values as well as common clinically available values in
           the conduct of the study so that results would be clinically relevant.

      This is a prospective observational study. Patients will be divided into two groups dependant
      upon the results of their heparin dose response test; sensitive or resistant. Two groups of
      thirty will be selected to achieve 90% power at the 0.025 level of significance using a
      one-sided two-sample t-test.

      The primary investigator will collect all data and submit the means to the statistician.
      Based on anecdotal experience the investigators expect there will be no difference between
      the two groups in terms of chest tube losses and transfusion events post-operatively.

      This work is quite relevant to the investigators daily practice. Every open heart patient is
      anticoagulated with heparin and bleeds post operatively. The investigators goal is a
      reproducibly safe anticoagulation level and an acceptable level of chest tube losses. This
      translates to getting patients out of the operating room in a timely fashion and minimizing
      transfusion events.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        On the date of surgery, the patient would be brought to the operating room. The first blood
        sample would be drawn prior to heparinization. This would include analysis for Activated
        Clotting Time, Heparin Concentration/Heparin Dose Response, antithrombin and
        Thrombelastograph. During this first sampling interval, the patient's Heparin Sensitivity
        or Resistance is determined by Heparin Dose Response (slope). The following values would
        determine which one of the two study groups the patient would be assigned:

          -  Sensitive to heparin: at or above 90 seconds/unit/millilitre

          -  Resistant to heparin: below 89 seconds/unit/millilitre
      
Keywords: Heparin Dose; Heparin Resistance; Chest Tube Losses; Transfusion Events