Protein C, protein S and C4b-binding protein in severe infection and septic shock

We measured concentrations of the natural anticoagulant protein C; its cofactor, protein S; and the carrier protein C4b-binding 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.