What is the optimal blood glucose target in critically ill patients? A nested cohort study

AIMS: There is an uncertainty about what constitutes an optimal level of blood glucose (BG) in critically ill patients. The objective of this study is to identify the optimal BG target for glycemic control in critically ill patients that is associated with survival benefit with the least hypoglycemia risk. SETTING AND DESIGN: This is a nested cohort study within a randomized control trial conducted in a tertiary care center in King Abdulaziz Medical City, Riyadh, Kingdom of Saudi Arabia. METHODS: The study was carried out in a single center to assess the effect of intensive insulin therapy [IIT; target BG 4.4-6.1 mmol/L (80-110 mg/dL)] versus conventional insulin therapy [CIT; target BG 10-11.1 mmol/L (180-200 mg/dL)] in a medical/surgical ICU. All patients were divided into six groups based on the mean daily BG levels. A logistic regression model was used to determine the association of BG and ICU mortality. We compared different outcomes below and above different BG thresholds of 0.1 mmol/L (2 mg/dL) increments using multivariate analyses. STATISTICAL ANALYSIS: Data are presented as mean ± SD or median with interquartile ranges, unless otherwise indicated. Differences between the six groups were assessed using the χ(2) test. A P-value equal or less than 0.05 was considered to indicate statistical significance. The results were expressed as adjusted odds ratio (aOR) and 95% confidence intervals (CI). Statistical analyses were carried out using the Statistical Analysis Software (SAS, release 8, SAS Institute Inc., Cary, NC, USA). RESULTS: Among six groups, the ICU mortality was least in patients with BG <8.7 mmol/L (<157 mg/dL) compared with patients with BG ≥8.7 mmol/L (≥157 mg/dL) [11.5% vs. 21.5%, P = 0.002]. When analyzed using 0.1 mmol increments in average BG, we found that mortality remained unchanged by increasing thresholds of BG up to 8.0 mmol/L (144 mg/dL) and started to rise with thresholds of BG of 8.1 mmol/L (146 mg/dL) and above. The risk of hypoglycemia was the highest with a BG threshold of 6.1 mmol/L (110 mg/dL) and gradually decreased with increasing BG levels to plateau with a BG level of 7.2 mmol/L (130 mg/dL) and higher. CONCLUSION: Our study suggests that a BG level of 8.1 mmol/L (146 mg/dL) and below represents an optimal level in critically ill patients.