Impairment of pulmonary macrophage function with total parenteral nutrition

The effects of total parenteral nutrition (TPN) administration on pulmonary macrophage function and host response to gram-negative pulmonary infection were evaluated.

Administration of TPN resulted in increased infectious complications in traumatized and perioperative patients, but underlying mechanisms are unclear.

Twenty-six male Wistar rats underwent central vein cannulation and were randomized to isocaloric feeding of a regular chow diet (RD) plus saline infusion or TPN without chow diet for 7 days. Pulmonary alveolar macrophage (PAM phi) superoxide production, Candida albicans phagocytosis and killing, and tumor necrosis factor (TNF) production in response to endotoxin (LPS) were assessed. Mesenteric lymph nodes (MLN) were cultured. A second group of rats (n = 6/group) were inoculated intratracheally with a sublethal dose of 9 x 10(9) live Escherichia coli per animal, and the lungs were cultured quantitatively 72 hours later to assess bacterial clearance. Finally, 11 RD-fed rats and 13 TPN-fed rats received intratracheal inoculation of 1.4 x 10(10) live E. coli and were included in follow-up.

Administration of TPN was associated with a significant increase in bacteria positive MLN compared with those in the RD group (p < 0.01). Pulmonary alveolar macrophage superoxide production, Candida albicans phagocytosis and killing, TNF production, and pulmonary clearance of bacteria were decreased significantly in TPN-fed rats compared with those fed a regular chow diet (p < 0.05). These pulmonary macrophage function changes were associated with a significantly higher mortality in TPN-fed rats compared with RD-fed rats after higher dose pulmonary E. coli inoculation.

Defective host pulmonary antimicrobial immune responses during TPN are associated with intestinal bacterial translocation, and may explain increased infectious complications.