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Administration of noradrenaline, adrenaline or dopamine resulted in persistent increases in VO2 in volunteers. With the exception of the transient adrenaline effect on fatty acids the metabolic actions were steady during 4 h of adrenergic stimulation. Since the adrenergic effect on VO2 is persistent over time a similar action in patients (e.g. septic shock) during treatment with adrenoceptor agonists may be important. Thus, an increase in VO2 during therapy may not only reflect an oxygen debt but also a pharmacodynamic action of adrenoceptor mediated calorigenic and metabolic induction.

The metabolic changes that occur after cardiac surgery result from a complex interaction between the effects of surgery and extracorporeal circulation per se, the inflammatory response to surgical trauma and extracorporeal circulation, perioperative use of hypothermia, the cardiovascular and neuroendocrine responses characteristic to cardiac surgery, and the drugs and blood products used to support circulation during and after operation. These changes include among others increased oxygen consumption and energy expenditure and increased secretion of insulin, growth hormone, adrenocorticotrophic hormone, cortisol, epinephrine and norepinephrine. Other changes include decreased total-Trijodthyronine levels, hyperglycemia, hyperlactatemia, increased glutamate, aspartate and free fatty acid concentrations, hypokalemia, an increased production of inflammatory cytokines and increased consumption of complement and adhesion molecules. There is evidence that better control of metabolic abnormalities improves the patients' outcome.

The objective of the present study was to evaluate the effects of norepinephrine (n = 9) and dobutamine (n = 7) on carbohydrate and protein metabolism in healthy volunteers in comparison with a control group (n = 9). Norepinephrine (0.1 microg/kg min), dobutamine (5 microg/kg min), or placebo was infused for 240 min. The plasma concentration of glucose, lactate, epinephrine, norepinephrine, insulin, and glucagon were determined. Glucose and urea production and leucine flux were measured using a tracer technique. Norepinephrine caused a persisting rise in plasma glucose concentration, whereas the increase in glucose production was only transient. A minor increase in plasma lactate concentration was observed, but it did not exceed the physiological range. No change in leucine flux, urea production, or plasma concentration of insulin, glucagon, or epinephrine was found. Dobutamine slightly decreased glucose production, whereas the plasma concentration of glucose and lactate did not change. The reduction in leucine flux was paralleled by a decrease in urea production. No change in the plasma concentration of insulin, glucagon, or the catecholamines was observed. In conclusion, both norepinephrine and dobutamine have only minor metabolic effects. Because glucose production is enhanced by alpha1- and beta2-adrenoceptor stimulation, we conclude that dobutamine is only a weak agonist at these adrenoceptors. These minor metabolic actions may make both compounds suitable for critically ill patients because no further increase in metabolic rate should be caused.

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Adrenaline induced an increase in glucose production lasting for longer than 240 min. The decrease in leucine and KIC flux suggests a reduction in proteolysis, which was supported by the decrease in urea production. The increase in alanine flux is therefore most likely due to an increase in de-novo synthesis. The ammonia donor for alanine synthesis in peripheral tissues and the target for ammonia after alanine deamination in the liver remain to be investigated. These results indicate that adrenaline infusion most probably will not promote already enhanced proteolysis in critically ill patients. Gluconeogenesis is an energy consuming process and an increase may deteriorate hepatic oxygen balance in patients.