  The approximation of the renormalized stress-energy tensor of the quantized
massive scalar, spinor, and vector field in the Reissner- Nordstrom spacetime
is constructed. It is achieved by functional differentiation of the lowest
order of the Schwinger-DeWitt effective action involving coincidence limit of
the Hadamard-Minakshisundaram-DeWitt-Seely coefficient a_{3}, and restricting
thus obtained general formulas to spacetimes with vanishing curvature scalar.
For the massive scalar field with arbitrary curvature coupling our results
reproduce those obtained previously by Anderson, Hiscock, and Samuel by means
of 6-th order WKB approximation.
