Abstract : It is little known that quantum dynamics problems can be solved by means of trajectories, resulting from Bohmian interpretation of quantum mechanics. The numerical propagation of these quantum trajectories constitutes however a real challenge, because of the difficulty in precisely evaluating the space derivative involved in the equations. In this thesis we present approximations allowing us to propagate the quantum trajectories without numerical instabilities. We are particularly interested in systems made up of several coupled electronic states. On the one hand, we develop a semi-classical approximation that uncouples the trajectory propagation from the electronic transitions. On the other hand, we apply to coupled-state systems a reformulation of the hydrodynamic equations in terms of the space derivatives of the phase and amplitude. In both cases, the formalism is established and applied numerically to model processes.