The strength of the present study is the repetitive measurements of glutamine Ra in critically ill patients, detecting a higher glutamine Ra during the glutamine containing dipeptide infusion. This finding would have been difficult to demonstrate if paired measurements had not been possible. Limitations of the present study are the fact that the measured glutamine Ra is an estimate of the endogenous glutamine production rate, and also the heavy dependence upon the correct baseline when calculating the AUC in the bolus injection technique. The latter may be overcome by employing a two-pool model, a suggestion that has to be validated.
The absence of a relationship between plasma glutamine concentration and the endogenous glutamine production rate in this pilot study calls for further exploration of the relationship between the two. The glutamine plasma concentrations in Figure 2 indicate that five patients had low values (