Lactic acidosis.

Many assumptions and compromises must be made in order to establish blood lactate as a reliable parameter of tissue oxygenation. One must think not only of reactions and cells as having oxidation-reduction potentials, but the concept of the redox potential of tissues, organs and even whole patients becomes applicable. Blood lactate concentrations probably are not an accurate measure of intracellular lactate. Thermodynamic equilibrium of the intracellular lactic acid dehydrogenase system cannot be assumed and, in fact, is probably not compatible with life. Clinically, however, the lactate-pyruvate system appears to establish a dynamic equilibrium that is responsive both to oxygen supply and substrate pyruvate availability. The diagnostic and prognostic values of blood lactate with both a stable and increased lactate to pyruvate ratio have been established empirically by numerous investigators. If evaluated within the constraints of available knowledge, blood lactate concentration is a valuable indicator of tissue perfusion and an effective surgical tool.