Sarah Bos

67 Hemostatic complications in hepatobiliary surgery 5 developing during partial hepatectomy, indicating that the decrease in ADAMTS13 following partial hepatectomy is only partly related to decreased synthetic capacity of the remnant liver. Although the function of the primary hemostatic system may be much better preserved during hepatobiliary surgery than suggested by the platelet count, the developing thrombocytopenia may affect the outcome. Platelets not only are critical in hemostasis but also appear to play a role in liver injury and regeneration. Animal studies have demonstrated that platelets contribute substantially to liver regeneration following partial hepatectomy,(27–30) although the mechanisms involved are incompletely understood.(31) In humans, it has been demonstrated that a low postoperative platelet count is associated with delayed liver function recovery after partial hepatectomy, which suggests that platelets play a critical role in liver regeneration after hepatectomy also in humans.(16,17,32,33) Also, a recent study in living donor transplant recipients demonstrated that in those recipients that did not receive intraoperative platelet transfusions, the intraoperative platelet count was positively associated with graft regeneration as assessed by graft volume measurements by computed tomography.(34) Secondary Hemostasis During partial hepatectomy and liver transplantation, plasma levels of coagulation factors and inhibitors decrease, which is likely related to a combination of hemodilution, consumption, and defective hepatic synthesis.(35,36) In patients with an uncomplicated postoperative course, nadir levels are reached within 24 hours, and coagulation proteins recover to normal levels in the first postoperative weeks.(37,38) The reduction in levels of procoagulant proteins results in a further prolongation in the PT, which suggests a hypocoagulable state.(38,39) In some samples taken during a liver transplant, the PT even becomes immeasurably high. (39) However, the reduction in procoagulants is accompanied by a reduction in natural anticoagulant proteins.(38,39) As the PT is only sensitive to plasma levels of procoagulant proteins; the test does not assess the net effect of concomitant alterations in levels of pro- and anticoagulant proteins. In addition, plasma levels of procoagulants appear to recover more quickly as compared with levels of anticoagulant proteins.(40) More advanced hemostatic tests including thrombomodulin-modified thrombin generation or thromboelastography, therefore, indicate normo- to hypercoagulability in these patients, despite prolongations in the PT.(39,41–46) Interestingly, one study has shown that a hypercoagulable TEG (Haemonetics Corp, Massachusetts, United States) as defined by a shortened r-time developed in as much as 30% of patients during the anhepatic phase of liver transplantation.(45)