A prospective randomized study of glutamine-enriched parenteral compared with enteral feeding in postoperative patients

Plasma amino acids were measured in 17 postoperative subjects randomly assigned to receive for ≤ 5 d tube feeding or total parenteral nutrition (TPN) that had identical energy, nitrogen, and glutamine contents. Subjects required gastric or pancreatic surgery for malignancy and were well-matched for age and body mass index. Tube feeding or TPN began on postoperative day 1 and advanced in daily 25% increments to meet goals of 105 kJ·kg body wt ^{- 1}·d^-1, 1.5 g protein·kg body wt ^-1·d^-1, and 0.3 g glutamine·kg body wt^-1·d^-1. Delivered energy, nitrogen, and glutamine were closely matched on day 4. Nitrogen balance and plasma proteins did not differ significantly between feeding groups. Total indispensable amino acids, branched-chain amino acids, and glutamine declined 25% on postoperative day 1 compared with preoperative day 0. Indispensable and branched-chain amino acid concentrations were restored with 5 d of either tube feeding or TPN. Glutamine concentrations did not differ significantly by feeding group, though a trend suggested that glutamine recovered more slowly in the tube- fed than in the TPN-fed subjects. Plasma amino acids otherwise reflected formula composition with ratios of valine to leucine of 1.24 and 3.69 μmol/L in subjects receiving 5 d of tube feeding or TPN, respectively. These findings suggest that glutamine-enriched tube feeding and TPN can result in similar profiles for most plasma amino acids at carefully matched doses.