Abstract
IntroductionGlutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production. Recently a technique employing a bolus injection of isotopically labeled glutamine was introduced, with the potential to allow for multiple assessments of the glutamine Ra over time in critically ill patients, who may not be as metabolically stable as healthy individuals. Here the technique was used to evaluate the endogenous glutamine production in critically ill patients in the fed state with and without exogenous glutamine supplementation intravenously.MethodsMechanically ventilated patients (n = 11) in the intensive care unit (ICU) were studied on two consecutive days during continuous parenteral feeding. To allow the patients to be used as their own controls, they were randomized for the reference measurement during basal feeding without supplementation, before or after the supplementation period. Glutamine Ra was determined by a bolus injection of 13C-glutamine followed by a period of frequent sampling to establish the decay-curve for the glutamine tracer. Exogenous glutamine supplementation was given by intravenous infusion of a glutamine containing dipeptide, L-alanyl-L-glutamine, 0.28 g/kg during 20 hours.ResultsA 14% increase of endogenous glutamine Ra was seen at the end of the intravenous supplementation period as compared to the basal measurements (P = 0.009).ConclusionsThe bolus injection technique to measure glutamine Ra to estimate the endogenous production of glutamine in critically ill patients was demonstrated to be useful for repetitive measurements. The hypothesized attenuation of endogenous glutamine production during L-alanyl-L-glutamine infusion given as a part of full nutrition was not seen.
Highlights
Glutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production
Exogenous glutamine supplementation is the standard of care when parenteral nutrition is required in critically ill patients [3,4]
Due to failure to detect any glutamine tracer in one of the measurements in one patient, results are only reported for 11/12 patients
Summary
Glutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production. There are several ways to measure and calculate glutamine Ra; by a constant infusion of isotopically labeled glutamine [6,7,8,9], by the use of increment curves or decay curves in conjunction with the start or end of a constant intravenous infusion of exogenous glutamine [10,11], and recently by a bolus injection of isotopically labeled glutamine [12]. These techniques show comparable results and may have inherent advantages or disadvantages when utilized in various clinical situations. The bolus injection technique allows for repeated measurements, and it only requires steady state assumption for a relatively short period of time
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