We hypothesized that the influence of cyanotic disease on postoperative blood loss is closely related to age in children undergoing cardiac surgery. Here, we demonstrate that the presence of a cyanotic disease is associated with increased postoperative blood loss in children aged 1 to 6 months. Children with cyanotic disease and aged<1 month who received fresh frozen plasma during cardiopulmonary bypass had less postoperative blood loss and higher maximal clot firmness on FIBTEM than cyanotic children from all other groups. Additional studies are needed to define optimal pathophysiology-based management in children undergoing cardiac surgery.