Pivotal Role of Lactate in Aerobic Energy Metabolism. In: Vincent J, editor. Yearbook of Intensive Care and Emergency Medicine 1998. Berlin: Springer Berlin Heidelberg; 1998. pp. 588-96. [DOI: 10.1007/978-3-642-72038-3_50]

Lactate metabolism in acute uremia

Lactate is a key metabolite that is produced by every cell and oxidized by most of them, provided that they do contain mitochondria. Its metabolism is connected to energetic homeostasis and the cellular redox state. It is well recognized as an indicator of severe outcome in severely ill patients, however, it is not a detrimental factor per se. Conversely, some recent data tend even to indicate a beneficial effect in several metabolic disorders. Although the liver has long been recognized as a key organ in lactate homeostasis, the kidney also plays a major role as a gluconeogenic organ significantly involved in the glucose-lactate cycle. In acute renal failure, sodium lactate is widely used as a buffer in replacement fluids because the anion (lactate - ) is metabolized and the cation (Na + ) remains, leading to decreased water dissociation and proton concentration. The metabolic disorders related to acute renal failure or associated with it, such as liver failure, may affect lactate metabolism, and therefore they are often regarded as limiting factors for the use of lactate-containing fluids in such patients. By investigating endogenous lactate production in severe septic patients with acute renal failure, we found that an acute exogenous load of lactate did not affect the basal endogenous lactate production and metabolism. This indicates that exogenous lactate is well metabolized even in patients suffering from acute renal failure and severe sepsis with a compromised hemodynamic status.

Metabolic and nutritional disorders in cardiac cachexia

Cardiac cachexia is divided into two types, i.e., the classic type, which occurs in patients with severe heart failure, and the nosocomial type, which develops in the postoperative state. Cardiac cachexia is due both to a decrease in nutrient intake (anorexia, malabsorption) and to specific metabolic alterations (hypercatabolism with increased energy expenditure, response to hypoxia, inflammatory status, etc). Among the various mechanisms involved in the pathogenesis of cachexia, cellular hypoxia has long been recognized. The chronic activation of the endogenous neurohormonal system is another specific feature of such patients; a striking relationship was found between cardiac cachexia and hormonal levels which correlate better than the classical parameters of cardiac failure severity. Finally, inflammatory syndrome has been known to occur frequently in patients with cardiac cachexia. Several studies have shown that tumor necrosis factor-alpha was significantly increased in cachectic patients and that chronic activation of the systemic immune response might be a common and unifying factor.