Summary
Venous occlusion of a limb is an established procedure for increasing the venous plasma
concentration of tissue plasminogen activator (t-PA). In this paper a simple haemodynamic
model was developed to describe the venous plasma t-PA concentration as a function
of haemodynamic parameters and the local release rate of t-PA during venous occlusion
of the limb. The venous plasma pool of a limb was regarded as a single well-mixed
compartment with a constant input rate of t-PA. The intravascular volume, blood flow
and total limb volume of the upper extremity were also measured in three healthy subjects
in order to characterise the haemodynamics during venous occlusion. Venous occlusion
was shown to cause such an intense decrease of blood flow through the limb that the
postocclusion increase in concentration of t-PA need not be explained by an increased
release rate of t-PA but could be attributed merely to the diminished dilution of
the venous compartment by inflowing arterial plasma. According to our model and haemodynamic
measurements, the significant differences in the postocclusion concentration of t-PA
between the arrn and leg can be explained by different local release rates of t-PA.
