Heparin Responses in Pediatric Patients Undergoing Cardiopulmonary Bypass.

Heparin is an anticoagulant or "blood thinner". Heparin is always given to patients undergoing open-heart surgery to prevent blood from clotting when a patient is placed on the heart-lung machine. Heparin works by combining with a protein in blood to prevent other proteins from working together to form a clot. The protein that heparin combines with seems to be different in infants and young children compared to adults. The purpose of this study is to determine which proteins in children have a direct impact on the way heparin works. We also want to see how this may change at different ages. We will enroll two age groups of children; birth to 2 years and 10 years or older. A total of 125 patients will be enrolled into this study. These patients will already be scheduled for open-heart surgery using a heart-lung machine. The testing involves taking blood samples when the patient is asleep for surgery; and later from their intravenous line, IV. They will all have IV's in place already because of the surgery. Therefore the study will cause no pain or discomfort for the patients who take part.