A hydrodynamic approach with a nonequilibrium equation of state is used to describe heavy ion collisions at medium energies. This approach includes describing the compression, dilution, and freeze-out stages of a hot spot formed during a heavy ion collision. The calculated energy spectra of protons and light ⁴ He, ⁷ Li, ⁹ Be fragments produced in the ¹⁴ N + ¹²⁴ Sn reaction at a ¹⁴ N ion energy of 32 MeV/nucleon are compared to experimental data.