ABSTRACT
Factor XII (FXII) deficiency presents as a prolonged activated partial thromboplastin time (aPTT) but is not associated with clinically significant bleeding. Activated clotting time (ACT) is used routinely to monitor anticoagulation with unfractionated heparin in patients undergoing cardiopulmonary bypass (CPB). The coagulation activator reagents in most ACT tests are dependent on adequate FXII concentrations to initiate contact factor coagulation pathways. We report the case of a 14.7 kg girl undergoing CPB with a pre-admission FXII concentration of <1% and aPTT >200 seconds. The child was transfused with fresh-frozen plasma to replenish FXII, allowing safe ACT monitoring of heparin anticoagulation throughout CPB.
Subject(s)
Factor XII Deficiency , Anticoagulants , Cardiopulmonary Bypass , Child , Factor XII Deficiency/complications , Factor XII Deficiency/surgery , Female , Heparin/therapeutic use , Humans , Partial Thromboplastin TimeABSTRACT
Coagulation factor XII (FXII) is a plasma serine protease that belongs to the contact activation complex responsible for initiating the intrinsic coagulation pathway. FXII deficiency is a rare congenital disorder that is not associated with an increased tendency for bleeding. However, as contact activation is impaired in FXII deficiency, both the celite- and kaolin-initiated activated clotting time (ACT) measurements are prolonged markedly, which poses a challenge for anticoagulation monitoring in patients undergoing cardiac surgery. The authors successfully have used the standard Hemochron Jr. ACT+ test, which is activated by silica and phospholipid in addition to kaolin, to monitor anticoagulation for cardiopulmonary bypass in two patients with severe FXII deficiency. The ACT+ test showed low baseline values, increased adequately in response to heparin, and decreased to baseline after protamine. Importantly, there was no abnormal intra- or postoperative bleeding nor any thrombotic complications. Furthermore, in vitro dose-response ACT+ testing of FXII-deficient blood with increasing heparin concentrations supports the use of ACT+ in FXII deficiency.
