When a child undergoes heart surgery, a heart lung machine is used to keep blood flowing while the child's own heart is stopped. After surgery, a significant amount of the child's own blood is left in this machine. In the case of small children, the relative amount of blood potentially lost to the child in this way is very large.

In older children, and those who have undergone less complicated surgery, this blood can all returned to the child. Giving the child back his or her own blood makes is less likely that the child will need a transfusion of donated blood.

However, in younger children, or in children who have undergone more complicated surgery, most or all of this blood is thrown away. This is because of worry that returning this blood may cause bleeding, and excessive bleeding is one of the most feared complications of heart surgery.

This project will explore a method whereby the red blood cells left in the heart lung machine can be returned to children without increasing the risk of bleeding. It will also carefully examine the exact causes of higher bleeding risk in children getting their own blood back so that in the future, all children can have their own blood returned at the end of surgery.

The primary hypothesis of this study is that in our study population, compared to re-infusion of residual CPB blood, re-infusion of only the red cell component of residual CPB blood, causes a lesser defect in clotting, leading to decreased hemorrhage and less post-operative blood loss.

The secondary objectives of this project are to document the effects on the clotting system of pump blood re-infusion by means of in laboratory testing. This work has not been done and is of crucial importance to future optimization of the use of pump blood. We expect to detect and quantify with significant accuracy any increased bleeding risk with our hemostatic profiling. This information will be invaluable in planning the safe introduction of residual CPB blood re-infusion smaller children and those with increase risk of postoperative blood loss. Furthermore, we will determine whether or not any of the potentially beneficial effects to the clotting system of returning all components of residual CPB blood, such as an increase in functioning platelets, or an increase in clotting factors, are realized. This information will determine the utility of pursuing means by which these non red cell components of residual CPB blood can be safely re-infused.

Induction of anesthesia, arterial and venous vascular catheter placement, heparin administration, cardiopulmonary bypass machine setup and priming, conduct of CPB, ultrafiltration of blood during CPB, post-CPB protamine administration and post-CPB blood ultrafiltration will all be standardized as per current clinical practice.

Residual CPB blood will be processed and re-infused according to group allocation.

Intravascular volume in the form of crystalloid, and blood products will be administered over and above the study residual blood product infusion as required according to protocol.

Subjects will have blood sampled for hemoglobin concentration immediately after induction of anesthesia and again 24 hours following their surgery.

Arterial blood will be sampled from the patient for a hemostatic profile, outlined in the adjacent text box, after separation from CPB and prior to initiation of residual CPB blood product re-infusion. A second sample will be obtained when re-infusion of residual CPB blood product is complete. In addition, a hemostatic profile will be run directly on a sample of the residual CPB blood product.

Subject demographic data, surgical diagnosis and procedures, CPB data, all medication, blood product and intravenous fluid administration, total volume of study fluid administered, blood lost during surgery to sponges and suction and 24 hour mediastinal drainage will be recorded for all subjects. Any cases of incomplete re-infusion of study blood product will be noted as will the reason for the occurrence.

Inclusion Criteria:

• Children between 15 and 30 kg undergoing cardiac surgery requiring cardiopulmonary bypass at British Columbia's Children's Hospital.
• All children will be between 2 and 10 years of age.
• Surgery will only involve single atriotomy.