  We analyze the effects of different coupling anisotropies in spin-1/2 ladder
on the Electron Spin Resonance (ESR) shift. Combining a perturbative expression
in the anisotropies with temperature dependent Density Matrix Renormalization
Group (T-DMRG) computation of the short range correlations, we provide the full
temperature and magnetic field evolution of the ESR paramagnetic shift. We show
that for well chosen parameters the ESR shift can be in principle used to
extract quantitatively the anisotropies and, as an example, discuss the
material $\mathrm{(C_5H_{12}N)_2CuBr_4}$ (BPCB).
