Use of tracer techniques in intensive care research. Part I

Glucose metabolism and catecholamines

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the beta2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of catecholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.