The shift of the critical point of dilute polymer solutions under shear was studied explicitly, by starting from the Rouse-Zimm model and from a thermodynamic model based on a non-equilibrium Gibbs free energy which includes non-equilibrium corrections. The thermodynamic criterion for the spinodal line is compatible with the dynamic analyses when the normal pressure effects along the velocity gradient may be neglected and when the fluctuations vary only along the velocity gradient direction. Our main result is that the hydrodynamic interactions between macromolecules reduce the shift in the spinodal line.