Effect of Glycemic Variability on Mortality in ICU Settings: A Prospective Observational Study

BACKGROUND: Evidence suggests a role of glycemic variability in intensive care unit (ICU) mortality. OBJECTIVE: To assess effect of glycemic variability and ICU/in-hospital mortality. DESIGN: Prospective, observational study. SETTING: A 20-bedded medical/surgical ICU in a tertiary care hospital. PATIENTS: Critically ill patients requiring life-support measures admitted to the ICU between November 1, 2015 and December 30, 2016 with hyperglycemia [random blood sugar (RBS) ≥200 mg%] and sequential organ failure assessment (SOFA) scores ≤9. Patients were put on predefined insulin infusion protocol, multiple glucose values were obtained, and mean blood glucose level (MGL) was calculated as their simple arithmetic mean. Standard deviation (SD) of MGL and coefficient of variation (CV) of glucose (derived as a percentage of SD to mean blood glucose) were then calculated for each patient and analyzed for all-cause death during hospitalization period. RESULTS: A total of 123 patients having a mean age of 65.12 ± 16.27 years, mean SOFA score of 5.76 ± 1.76, and mean HbA1c of 6.22 ± 0.73% were included. MGL was 160.65 ± 24.19 mg/dl, SD 33.32 ± 15.08 mg/dl, and CV 20.74 ± 8.43. Deceased as compared to survivors had higher MGL (163.76 ± 24.85 vs 155.62 ± 22.43 mg/dl, P = 0.068) and higher glycemic variability (SD 38.92 ± 14.44 vs 25.06 ± 12.27 mg/dl; P < 0.001 and CV 23.69 ± 7.9 vs 15.98 ± 6.87; P < 0.001). Interestingly, more patients having higher CV at lower MGL (85.7%) died as compared to those having lower CV at higher MGL (55.6%). CONCLUSIONS: High glycemic variability is associated with increased ICU/in-hospital mortality. Outcome of patients having less glycemic variability even with slight hyperglycemia may be better than those having tight glycemic control but higher glycemic variability. Insulin protocols need to be in place for management of hyperglycemia in critical care setting aiming for adequate glycemic control as well as minimizing glycemic variability.