U-shaped relationship between early blood glucose and mortality in critically ill children

Abstract

Background: The aims of this study are to evaluate the relationship between early blood glucose concentrations and mortality and to define a 'safe range' of blood glucose concentrations during the first 24 h after pediatric intensive care unit (PICU) admission with the lowest risk of mortality. We further determine whether associations exist between PICU mortality and early hyperglycemia and hypoglycemia occurring within 24 h of PICU admission, even after adjusting for illness severity assessed by the pediatric risk of mortality III (PRISM III) score.

Methods: This retrospective cohort study included patients admitted to PICU between July 2008 and June 2011 in a tertiary teaching hospital. Both the initial admission glucose values and the mean glucose values over the first 24 h after PICU admission were analyzed.

Results: Of the 1349 children with at least one blood glucose value taken during the first 24 h after admission, 129 died during PICU stay. When analyzing both the initial admission and mean glucose values during the first 24 h after admission, the mortality rate was compared among children with glucose concentrations ≤ 65, 65-90, 90-110, 110-140, 140-200, and >200 mg/dL (≤ 3.6, 3.6-5.0, 5.0-6.1, 6.1-7.8, 7.8-11.1, and >11.1 mmol/L). Children with glucose concentrations ≤ 65 mg/dL (3.6 mmol/L) and >200 mg/dL (11.1 mmol/L) had significantly higher mortality rates, indicating a U-shaped relationship between glucose concentrations and mortality. Blood glucose concentrations of 110-140 mg/dL (6.1-7.8 mmol/L), followed by 90-110 mg/dL (5.0-6.1 mmol/L), were associated with the lowest risk of mortality, suggesting that a 'safe range' for blood glucose concentrations during the first 24 h after admission in critically ill children exists between 90 and 140 mg/dL (5.0 and 7.8 mmol/L). The odds ratios of early hyperglycemia (>140 mg/dL [7.8 mmol/L]) and hypoglycemia (≤ 65 mg/dL [3.6 mmol/L]) being associated with increased risk of mortality were 4.13 and 15.13, respectively, compared to those with mean glucose concentrations of 110-140 mg/dL (6.1-7.8 mmol/L) (p <0.001). The association remained significant after adjusting for PRISM III scores (p <0.001).

Conclusions: There was a U-shaped relationship between early blood glucose concentrations and PICU mortality in critically ill children. Both early hyperglycemia and hypoglycemia were associated with mortality, even after adjusting for illness severity.

Figure 1

PICU Mortality rates according to different admission glucose cutoff values. PICU, pediatric intensive care unit. Curve represents a polynomial trendline. p value: comparison to children with admission blood glucose of 110 to 140 mg/dL (6.1 to 7.8 mmol/L). **p <0.01. Probability values: Chi-square test

Figure 2

PICU Mortality rates according to different mean glucose cutoff values. PICU, pediatric intensive care unit. Curve represents a polynomial trendline. p value: comparison to children with mean blood glucose of 110 to 140 mg/dL (6.1 to 7.8 mmol/L). *p <0.05, **p <0.01. Probability values: Chi-square test

Figure 3

PICU Mortality rates according to different mean glucose cutoff values, stratified by PRISM III score. PICU, pediatric intensive care unit; PRISM III, pediatric risk of mortality III. p value: comparison to children with mean blood glucose of 110 to 140 mg/dL (6.1 to 7.8 mmol/L). **p <0.01. Probability values: Chi-square test or Fisher’s exact test