Conversion from Continuous Insulin Infusions to Subcutaneous Insulin in Critically III Patients

BACKGROUND: Continuous insulin infusions have become a standard of care in many intensive care units (ICUs); however, methods for transitioning patients from continuous infusions to other insulin therapies have not been extensively evaluated. OBJECTIVE: To determine the most effective method for transitioning ICU patients from continuous insulin infusions to subcutaneous insulin therapy. METHODS: A searchable pharmacy database at the University of North Carolina Hospitals was used to retrospectively identify adults admitted to the neurosurgery ICU and prescribed a continuous insulin infusion between May 2007 and February 2008. All patients were transitioned to subcutaneous insulin upon floor transfer. Patients were stratified according to the dose of subcutaneous insulin as a percentage of their prior 24-hour continuous insulin requirement and then analyzed on the rate of achievement of goal blood glucose values (80-150 mg/dL) within the first 48 hours after transition. RESULTS: A total of 769 blood glucose values from 79 patients were recorded during the study. Data analysis demonstrated significantly lower median blood glucose values with the use of subcutaneous insulin doses that were 60-70% of insulin infusion requirements when compared with all other groups. For patients without a history of diabetes mellitus, the use of a subcutaneous dose that was 60-70% of the insulin infusion requirement resulted in a significantly greater percentage of patients within the target range compared with other groups (78%; p < 0.05). For those with a history of diabetes, subcutaneous doses higher than 70% of the insulin infusion requirement yielded the most frequent achievement of target values, although there was substantial variability within this group. No significant difference was noted in the incidence of hypoglycemia (blood glucose < 80 mg/dL) between groups, although the frequency of hypoglycemia was almost twice as high in the group with diabetes as in those without it (4.2% vs 2.2%). CONCLUSIONS: Methods currently used to transition patients off insulin infusions vary widely. Initial data suggest that utilizing 60-70% of the 24-hour insulin infusion requirement as a subcutaneous dose would result in blood glucose values of 80-150 mg/dL 70% of the time. Further study is necessary to adequately assess the optimal insulin infusion transition protocol for critically ill patients to ensure both safety and efficacy.