MONITORING OF HEMOSTASIS DURING LIVER SUR GERY

Bleeding is causally related to about 50% of postoperative deaths foll owing liver resection. Main factors contributing to increased perioper ative bleeding in liver surgery include surgical trauma, reduced activ ity of clotting factors and inhibitors due to impaired hepatic synthes is, low platelet count and poor platelet function as well as impaired clearance of activated clotting factors by the reticuloendothelial sys tem of the liver (Kupffer cells). Hemostasis may be further impaired b y transfusion of blood components, since citrate added for conservatio n is not adequately metabolized by the failing liver. Surgical bleedin g leads to a loss of pro- and anticoagulatory factors as well as to ac tivation of coagulation. Finally, hyperfibrinolysis induced by release of tissue plasminogen activator (t-PA, primary hyperfibrinolysis) and disseminated coagulation (secondary hyperfibrinolysis) contribute to increased bleeding. Therefore early diagnosis and treatment of coagula tion disorders is of paramount importance during liver surgery. Screen ing parameters of hemostasis and fibrinolysis should be available on a 24-hour basis in centers performing liver surgery. Screening for diso rders of secondary hemostasis includes evaluation of prothrombin time (PF), activated partial thromboplastin time (aPTT), fibrinogen concent ration and the activity of the most important inhibitor, antithrombin III (AT III). Thrombelastography is the leading method for diagnosis o f hyperfibrinolysis, which can also be assessed by determination of D- dimer, fibrinogen and fibrin degradation products. Evaluation of prima ry hemostasis is frequently restricted to platelet count, which is onl y a rough parameter. In contrast, measurement of in vitro bleeding tim e and volume enables repeated quantification of platelet function in p atients with impaired hemostasis.