Plasma glutamine concentration after intensive care unit discharge: an observational study

Abstract

Introduction: Low plasma glutamine concentration at ICU admission is associated with unfavorable outcomes. The prediction of plasma glutamine concentration after ICU discharge on outcomes has not been characterized. In the recent Scandinavian Glutamine Trial, a survival advantage was seen with glutamine supplementation as long as patients stayed in the ICU. It was therefore hypothesized that the glutamine level may drop at ICU discharge, indicative of a sustained glutamine deficiency, which may be related to outcome.

Methods: Fully fed ICU patients intravenously supplemented with glutamine for >3 days were studied at ICU discharge and post ICU. In study A, plasma glutamine level was followed every 5 to 7 days post ICU of the remaining hospital stay and compared to the level on the day of ICU discharge (n=63). In study B, plasma glutamine level 24 to 72 hours after ICU discharge was related to 12-month all-cause mortality (n=100).

Results: Post-ICU plasma glutamine levels were within normal range and were not found to be predictive for mortality outcome. Plasma glutamine level at discharge, on the other hand, was within normal limits but higher in nonsurvivors. In addition, it was adding prediction value to discharge SOFA scores for post-ICU mortality.

Conclusions: Post-ICU glutamine levels are not indicative of glutamine depletion. The relation between plasma glutamine concentration and glutamine availability during critical illness is not well understood, and needs to be studied further to define the possible role for glutamine supplementation.

Figure 1

CONSORT diagrams on patients screened and included in the studies. Patients admitted to the ICU) and given exogenous intravenous glutamine supplementation together with full nutrition for >3 days were eligible. (A) describes patients sampled on their last day of ICU stay and thereafter every 5 to 7 days during the remaining hospital stay. Mortality, dropouts and ICU readmissions are indicated. (B) describes patients discharged from the ICU and sampled 24 to 72 hours after discharge. Mortality and dropouts are indicated. ICU, intensive care unit.

Figure 2

Post-ICU plasma glutamine concentrations of patients (n = 49), admitted to the ICU and given exogenous intravenous glutamine supplementation together with full nutrition for >3 days. Patients were sampled on their last day of ICU stay (during ongoing intravenous supplementation) and thereafter every 5 to 7 days during the remaining hospital stay. All patients are depicted in (A). The reference interval used in the study, 400 to 930 μmol/L is indicated by gray shading. (B) only illustrates patients who were not readmitted to ICU (n = 35), where the nonsurvivors at 12 months (n = 7) are shown as red lines. (C) illustrates patients who were readmitted to the ICU (n = 14), nonsurvivors at 12 months (n = 8) are shown as red lines. Thick lines illustrate periods during which patients in this subgroup were again given intravenous glutamine supplementation during full feeding. ICU, intensive care unit.

Figure 3

Plasma glutamine concentrations in ICU patients given exogenous intravenous glutamine supplementation together with full nutrition for >3 days and who were discharged alive from ICU, in relation to 12-month, post-ICU mortality. (A) illustrates discharge glutamine level (n = 63), and (B) illustrates glutamine levels 24 to 72 hours post discharge (n = 92). Discharge glutamine level during ongoing intravenous supplementation but not post-ICU glutamine level was associated with mortality outcome. Gray shading indicates the reference interval used, 400 to 930 μmol/L. Horizontal lines indicate median values. ICU, intensive care unit.