Endogenous glutamine production in mechanically ventilated patients on full nutrition in the ICU (n = 11) as assessed by measurements of glutamine R
using the bolus injection technique employing 13C-glutamine. The basal measurement was performed immediately before the start of exogenous intravenous glutamine supplementation with L-alanyl-L-glutamine (filled symbols, n = 6), or after a washout period of 4 h following the termination of the intravenous glutamine supplementation with L-alanyl-L-glutamine (open symbols, n = 5). Mean values with SD are indicated by filled squared symbols. **Increase in glutamine Ra statistically significant, P = 0.009.