Metabolic intervention in surgical patients: the effect of alpha- or beta-blockade on glucose and protein metabolism in surgical patients receiving total parenteral nutrition.

We performed a series of isotopic studies on the role of alpha- or beta-adrenergic activity in the regulation of glucose and protein metabolism in a group of surgical patients receiving total parenteral nutrition. We quantitated rates of glucose turnover and net protein breakdown by the primed constant infusion of 3H-glucose and 14C-urea, respectively. Basal measurements were first performed, and then the effect of either alpha- or beta-adrenergic blockade was assessed by means of the constant infusion of either phentolamine or propranolol. In addition, we assessed the effect of beta-stimulation by infusing the beta-agonist, salbutamol. The institution of alpha-adrenergic blockade did not significantly alter either the plasma glucose level or the rate of glucose production. However, the rate of net protein catabolism decreased significantly after alpha-adrenergic blockade. Before alpha-blockade the value for NPC was 0.88 +/- 0.27 gm/kg/day, and after alpha-blockade the corresponding value was 0.73 +/- 0.24 gm/kg/day (p less than 0.01). beta-Adrenergic blockade resulted in a decrease in the rate of glucose appearance from 38.2 +/- 6.1 mumol/kg/min to 35.1 +/- 5.7 mumol/kg/min, and the plasma glucose clearance increased from 5.0 +/- 0.8 ml/kg/min to 5.4 +/- 0.8 ml/kg/min. As a result of these changes the plasma glucose concentration decreased significantly (p less than 0.01) from 7.4 +/- 0.3 mumol/ml to 6.5 +/- 0.5 mumol/ml. beta-Adrenergic blockade did not significantly decrease the rate of net protein catabolism. beta-Stimulation with salbutamol resulted in a significant increase (p less than 0.05) in the rate of glucose production from 31.3 +/- 4.2 mumol/kg/min to 38.0 +/- 6.5 mumol/kg/min, and as a result the plasma glucose level increased significantly from 6.7 +/- 0.6 mumol/ml to 7.4 +/- 0.6 mumol/ml (p less than 0.04). We conclude from these studies that the role of the adrenergic nervous system in the promotion of endogenous glucose turnover in surgical patients receiving total parenteral nutrition is primarily a beta-adrenergic effect, whereas the promotion of protein catabolism is mainly an alpha-adrenergic effect.