Protein C, Protein S and c4b-Binding Protein in Severe lnfection and Septic Shock

Summary We measured concentrations of the natural anticoagulant protein C; its cofactor, protein S; and the carrier protein C4bbinding protein (C4BP), in 24 patients with severe infection and 13 with septic shock. Decreased antithrombin III levels were found in 16 of 24 infection patients and all shock patients; high thrombin-antithrombin (TAT) complexes were present in 16 of 24 infection and 12 of 13 shock patients. Protein C concentrations were significantly reduced compared to healthy blood donors, to 60 ± 14% (infection) and 47 ± 20% (septic shock) (mean ± 1 SD). Total protein S levels were not reduced (119 ± 36.7 and 88 ± 20.0%, normal value 96±15%). Free protein S was also normal (27 ± 9.4 and 30 ± 8.7%, normal value 29 ± 9%). The percentage free of total protein S was normal in shock patients (35 ± 8.5%), but significantly reduced in patients without shock (23 ± 5.3%). C4BP was significantly higher than normal in the latter group (135 ± 43%), but not in the shock group (118 ± 40%), possibly due to increased consumption. Thus, no deficiency of total or free protein S was found in these patients, who had evidence of activated coagulation but no clinical DIC.