Abstract
Background: Effect of diabetes and optimal range of blood glucose level on the short-term prognosis in patients with critical illnesses are currently ambiguous. We aimed to determine whether diabetes affects short-term prognosis and optimal range of blood glucose level for critically ill patients.Methods: We performed a retrospective analysis of data on 46,476 critically ill patients from the critical care database (version 1.4), collected prospectively between 2002 and 2012. Association of diabetes with 28-day mortality was assessed by inverse probability weighting based on the propensity score. Smoothing splines and threshold effect analysis were applied to explore the optimal glucose range.Results: Of the 33,680 patients enrolled in the study, 8,701 (25.83%) had diabetes. In the main analysis, the 28-day mortality was reduced by 29% (hazard ratio (HR)=0.71, 95% confidence interval (CI) 0.67-0.76) in patients with diabetes compared to those without diabetes. The E-value of 2.17 indicated robustness to unmeasured confounders. The effect of the association between with diabetes and 28-day mortality was generally in line for all subgroup variables, significant interactions were observed for glucose at ICU admission, admission type, and insulin use (Interaction P <0.05). A V-shaped relationship was observed between glucose and 28-day mortality in patients without diabetes, with the lowest 28-day mortality corresponding to the glucose level was 101.75 mg/dl (95% CI 94.64-105.80 mg/dl), and hypoglycemia or hyperglycemia should be avoided, especially in patients admitted to the surgical intensive care unit (SICU), cardiac surgery recovery unit (CSRU), and coronary care unit (CCU); for patients with diabetes, no optimal threshold for glucose was found, and elevated blood glucose does not appear to be associated with a poor prognosis, and perhaps may be beneficial except for CCU and CSRU.Conclusions: The non-detrimental effect of diabetes on the short-term prognosis of critically ill patients was further confirmed, which would reduce 28-day mortality by approximately 29%. For patients without diabetes, the glucose level corresponding to the lowest 28-day mortality was 101.75 mg/dl (95% CI 94.64-105.80 mg/dl); however, for patients with diabetes, the appropriate optimal blood glucose threshold remains unresolved.