Four patients with metabolic and/or circulatory failure are described. The clinical, biological and radiologic features of reversible renal failure with renal tubular acidosis are presented. A case of male breast carcinoma is discussed with reference to the effect of steroids on the hormonal receptors at the malignant cell. The pathophysiology of thrombotic thrombocytopenic purpura and its treatment (splenectomy and platelet aggregation inhibitors) are discussed. An overview of eclampsia and its relationship to underlying kidney disease is presented. It may be concluded that a metabolic and/or ischemic imbalance interferes with the normal activity of the reticular substance and the brainstem, which normally maintain the state of consciousness.