A pseudo steady-state model is proposed to analyze the effects of a vessel-length, blood-flow velocities, and the concentration levels of Va/Xa/phospholipid complex on the formation of thrombin in an arterial vessel. The outlet concentrations of thrombin are calculated in either physiological or pathological coagulation process. Among those factors, blood-flow velocity is the most important factor which affects the amount of thrombin formation. The model and its results might be used as a reference for those who clinically manage coagulation problems of patients with severe sepsis. Model Sepsis Blood-flow velocity Kinetic factors Thrombin formation nM nM nM nM pm2 set-' ,um* see-' nM FM nM min-' nM min-' mm seer mm sect' NOMENCLATURE concentration of ESAlOA concentration THB concentration of PTHB inlet concentration of PTHB to the vessel diffusivity coefficient for THB diffusivity coefficient for PTHB apparent Michaelis constant for the THB kinetic reaction Peclect number for THB (V,,.RID,,) Peclect number for THB (I',,,,,-RI&.& radius of the vessel THB kinetic rate equation PTHB kinetic rate equation for the conversion of PTHB to THB maximum flow velocity of stream in the vessel flow velocity of stream in the vessel dimensionless axial length (z/R) rate constant for the THB kinetic reaction (min-') radial distance from the center of the vessel @m) longitudinal distance from entrance of the vessel dimensionless radius (r/R) dimensionless concentration of PTHB ([PTHB]/[PTHB],J dimensionless concentration of THB ([THB]/[PTHB],) dimensionless reaction group for PTHB ( R2* k,/D,,,), dimensionless reaction group for THB (R* . DTHB)