Insulin therapy associated relative hypoglycemia during critical illness

Purpose: In critically ill diabetes patients, relative hypoglycemia (RH) (a decrease in glucose ≥30% below pre-admission levels, as estimated by HbA1c) is associated with greater mortality and absolute hypoglycemia. We investigated the epidemiology and outcomes of RH when it was associated with insulin therapy. Methods: We performed retrospective analysis of a cohort of critically ill patients with diabetes who received insulin in the intensive care units (ICUs) of a tertiary hospital. The primary outcome was 28-day mortality with respect to insulin therapy associated relative hypoglycemia (ITARH). Results: ITARH occurred in 184 (42%) of insulin-treated patients. ITARH was associated with a higher HbA1c (8.6% vs 6.6%, p < 0.001), a higher glycemic variability index (121 vs 75.1 mmol²/L²/h/week, p < 0.001) and more absolute hypoglycemia (18.5% vs 3.94%, p < 0.001). Its frequency peaked about 5 h after initiation of insulin therapy. ITARH was associated with a greater risk of subsequent hypoglycemia (adjusted HR 3.5, 95% CI 1.7–6.8) but not mortality (HR 1.2, 95% CI 0.7–2.2). Conclusions: ITARH is common in insulin treated critically ill diabetes patients and associated with poorer glycemic control. Unlike reports of RH in general, it is not associated with mortality, suggesting that the prognostic implications of RH differ according to its context.