Accelerated lung amino acid release in hyperdynamic septic surgical patients

Amino acid flux across the lungs was studied in humans to gain further insight into the altered nitrogen metabolism that characterizes catabolic disease states. Lung flux of glutamine, glutamate, and alanine was determined in three groups of surgical patients with indwelling pulmonary artery catheters: (1) preoperative controls (n = 14), (2) postoperative elective general surgical patients (n = 10, and (3) hyperdynamic septic surgical patients (n = 17). In controls the lung was an organ of amino acid balance. These exchange rates did not change in general surgical patients. In the septic group, glutamine release by the lung increased markedly from a control value of 0.80 +/- 0.99 mumol/kg per minute to 6.80 +/- 1.32 mumol/kg per minute. This accelerated release rate was secondary to both an increase in total pulmonary blood flow and an increase in the pulmonary artery-systemic arterial concentration difference. The lung also became an organ of significant alanine release in septic patients. The lung plays an active metabolic role in the processing of amino acids and may be a key regulator in interorgan nitrogen flux after major injury and infection.