Prevalence of glutamine deficiency in ICU patients: a cross-sectional analytical study

Abstract

Background: Not only is glutamine deficiency an independent predictor of mortality in intensive care unit (ICU) patients, but glutamine supplementation is also recommended for its proven outcome benefits. However, recent data suggest that early glutamine supplementation in certain patient groups increase mortality. The aim of this study was to investigate plasma glutamine levels of adult ICU patients in the South African setting and to determine relationships between glutamine levels, gender, diagnostic categories and selected inflammatory markers. The data from this study will be used as baseline measurement to support a large scale study that will be undertaken in the South African ICU population.

Methods: This cross-sectional, analytical study included 60 mixed adult ICU patients within 24 h post ICU admission. Plasma glutamine levels were determined on admission. The relationship between glutamine levels, Interleukin-6 (IL-6) and C-reactive protein (CRP); as well as gender- and diagnosis-related differences in glutamine levels were also investigated. A non-parametric ROC curve was computed to determine the CRP concentration cut-off point above which glutamine becomes deficient.

Results: The median plasma glutamine level (497 μmol/L) was in the normal range; however, 38.3 % (n = 23) of patients had deficient (<420 μmol/L) and 6.7 % (n = 4) had supra-normal glutamine levels (>930 μmol/L). No significant difference could be detected between glutamine levels and gender or diagnosis categories as a group. When only the medical and surgical categories were compared, the median plasma glutamine level of the medical patients were significantly lower than that of the surgical patients (p = 0.042). Glutamine showed inverse associations with CRP levels (r = -0.44, p < 0.05) and IL-6 concentrations (r = -0.23, p = 0.08). A CRP cut-off value of 95.5 mg/L was determined above which glutamine levels became deficient.

Conclusions: About a third of patients (38 %) were glutamine deficient on admission to ICU, whereas some presented with supra-normal levels. While glutamine levels correlated inversely with inflammatory markers, and a CRP value of above 95.5 mg/L indicated potential glutamine deficiency, the clinical application of this finding needs further investigation.

Keywords: C-reactive protein; Gender; Glutamine; Intensive care unit; Interleukin-6.

Fig. 1

Relationship between plasma glutamine and interleukin-6 levels (r = −0.23, p = 0.08)

Fig. 2

Relationship between plasma glutamine and CRP levels (r = −0.44, p < 0.05). CRP, C-reactive protein

Fig. 3

The receiver operating characteristic curve, computing the C-reactive protein level above which glutamine becomes deficient. Area under curve (AUC): 0.759 (95 % CI 0.653; 0.865, p < 0.0001)

Fig. 4

Plasma glutamine levels presented per interleukin-6 category. The area between the dashed lines represents normal plasma glutamine reference ranges. GLN, glutamine; IL-6, interleukin-6

Fig. 5

Plasma glutamine levels presented per C-reactive protein category. The area between the dashed lines represents normal plasma glutamine reference ranges. GLN, glutamine; CRP, C-reactive protein