Insulin infusion and hypoglycemia: clinical implications and prevention

Hypoglycaemia and predisposing factors among clinical subgroups treated with intensive insulin therapy

BACKGROUND

In previous studies, conflicting intensive insulin therapy (IIT) results have been observed, whereby IIT-related mortality seems to be lower in specific clinical subgroups. The aim of this study was to assess differences in glycaemic control, the risk of critical hypoglycaemia (≤ 2.2 mmol/l), the associated predisposing factors, and the in-hospital mortality in different clinical subgroups treated with IIT.

METHODS

Prospective, observational study in a university-affiliated intensive care unit (ICU) conducted from 2004 to 2005. All patients (n = 1667) belonging to one of the six most common surgical intervention groups (cardiac, neuro, abdominal, vascular, orthopaedic, and spinal surgeries) and medical patients were included. IIT was performed with a target blood glucose level of 4.4-7.8 mmol/l. Different indices were analysed to evaluate glucose control and glycaemic variability.

RESULTS

The rate of critical hypoglycaemia was significantly different within the different clinical subgroups and varied from 0.8% to 4.5%. Similar results were obtained for hyperglycaemia. Multivariable analyses for the predisposing factors of critical hypoglycaemia showed a heterogeneous distribution pattern among the different clinical subgroups. Similar results were obtained for the risk factors of in-hospital mortality.

CONCLUSION

The risk of critical hypoglycaemia and the associated predisposing factors depended on the clinical subgroup involved. Critical hypoglycaemia is a potential threat for our patients, and the high risk of critical hypoglycaemia in some clinical subgroups appeared to reverse the benefits of IIT. As a result, it is crucial that the different subgroups involved in a study are defined to further interpret the potential benefits of IIT and the risk of critical hypoglycaemia.

Intensive insulin therapy in critically ill hospitalized patients: making it safe and effective

Intensive insulin therapy (IIT) for hyperglycemia in critically ill patients has become a standard practice. Target levels for glycemia have fluctuated since 2000, as evidence initially indicated that tight glycemic control to so-called normoglycemia (80-110 mg/dl) leads to the lowest morbidity and mortality without hypoglycemic complications. Subsequent studies have demonstrated minimal clinical benefit combined with greater hypoglycemic morbidity and mortality with tight glycemic control in this population. The consensus glycemic targets were then liberalized to the mid 100s (mg/dl). Handheld POC blood glucose (BG) monitors have migrated from the outpatient setting to the hospital environment because they save time and money for managing critically ill patients who require IIT. These devices are less accurate than hospital-grade POC blood analyzers or central laboratory analyzers. Three questions must be answered to understand the role of IIT for defined populations of critically ill patients: (1) How safe is IIT, with various glycemic targets, from the risk of hypoglycemia? (2) How tightly must BG be controlled for this approach to be effective? (3) What role does the accuracy of BG measurements play in affecting the safety of this method? For each state of impaired glucose regulation seen in the hospital, such as hyperglycemia, hypoglycemia, or glucose variability, the benefits, risks, and goals of treatment, including IIT, might differ. With improved accuracy of BG monitors, IIT might be rendered even more intensive than at present, because patients will be less likely to receive inadvertent overdosages of insulin. Greater doses of insulin, but with dosing based on more accurate glucose levels, might result in less hypoglycemia, less hyperglycemia, and less glycemic variability.