Abstract: A cerebral function improving agent containing as the active ingredient a compound represented by the following formula: wherein R2 represents a hydrogen atom when R1 is a hydroxyl group; or R1 and R2 in combination represent an oxo group; R3 represents a hydrogen atom, an alkali metal, or a monohydric, dihydric or trihydric alcohol residue; which may be an oligomer composed of 2-10 molecules when R1 represents a hydroxyl group and R2 and R3 represent hydrogen atoms. The agent supresses cerebral edema, protects cerebral function, activates cerebral metabolisms and reduces the extent of cerebral infarction.

Abstract: A cerebral function improving agent containing as the active ingredient a compound represented by the following formula: ##STR1## wherein R.sub.2 represents a hydrogen atom when R.sub.1 is a hydroxyl group;or R.sub.1 or R.sub.1 are combined together to form an oxo group;R.sub.3 represents a hydrogen atom, an alkali metal, or a monohydric, dihydric or trihydric alcohol residue,which may be an oligomer composed of 2-10 molecules when R.sub.1 represents a hydroxyl group and R.sub.2 and R.sub.3 represent hydrogen atoms.The agent suppresses cerebral edema, protects cerebral function, impaired cerebral energy metabolism, and reduces the extent of cerebral infarction.

Abstract: The present invention provides a substitution fluid preparation which is characterized by containing at least one selected from 3-hydroxybutyric acid, 3-sodium hydroxybutyrate and 3-potassium hydroxybutyrate. The substitution fluid preparation of the present invention can be easily metabolized in the body of a patient to provide a good energy source and is also effective for suppressing increased protein catabolism in the living body.