[Simulation of transcapillary exchange of liquids]

The transcapillary exchanges of liquids between vascular and interstitial sections can be described with the help of a mathematical model describing variation in filtration, reabsorption, plasmatic flux and lymphatic flow in relation to the different active pressures, that is to say the arteriolar and venular pressures, the oncotic pressures of the proteins, and interstitial pressure. Also taking into account the modifications of the volemia in relation to blood loss and perfusions, modifications of the essential haemodynamic variables and diuresis, it is possible to reproduce various situations following the reduction in venous or lymphatic return, hypovolemia, and hypoproteinemia. The advantages in these simulations is demonstrated by the example of a blood depletion, compensated or otherwise, as follows: volemia, proteinemia, lymphatic flow. These simulations permit us to follow the sequence of events accompanying haemodilution, and to assess the qualities of a plasmatic substitute: oncotic strength, demi-vie, effect on the extravascular mobilisation of proteins. They also provide a reflexion tool permitting a better comprehension of transcapillary exchanges and the optimisation of strategies of vascular refill.