  For slowly rotating fluids, we establish the existence of a critical point
similar to the one found for non-rotating systems. As the fluid approaches the
critical point, the effective inertial mass of any fluid element decreases,
vanishing at that point and changing of sign beyond it. This result implies
that first order perturbative method is not always reliable to study
dissipative processes ocurring before relaxation. Physical consequences that
might follow from this effect are commented.
