Intentional Large Insulin Overdose Captured on a Continuous Glucose Monitor

Abstract

Continuous glucose monitoring (CGM) technology has emerged as an important diabetes management tool. Use of CGM with real-time glucose data can improve glycemic control with reduction in HbA1c and reduced time spent in hypoglycemia in both children and adults with type 1 diabetes. The magnitude of clinical benefit is related to duration of use. 1 Despite the advantages of CGM, it has not been widely integrated into routine management of type 1 diabetes. T1D exchange data demonstrates that CGM technology is being used by only 6.5% of people with type 1 diabetes in United States and that among individuals who have used CGM, twothirds stopped using it. 2 One of the major challenges facing widespread adoption of CGM technology is reduced accuracy and reliability of CGM systems, with a subsequent negative impact on adherence and effectiveness. 3 We present a case of deliberate insulin overdose in a person with type 1 diabetes wearing blinded CGM, highlighting the issue of accuracy of existing CGM systems in the hypoglycemic range. CaseA 25-year-old man with poorly controlled type 1 diabetes which had been diagnosed at the age of 10 years. His complications include laser-treated preproliferative retinopathy, microalbuminuria, and recurrent diabetic ketoacidosis. He has a personality disorder with multiple previous presentations with deliberate self-harm including insulin overdose. A Medtronic iPro2 blinded CGM system using an Enlite sensor (Medtronic, Northridge, CA) was arranged for 7 days to guide intensification of insulin therapy. On day six of monitoring, he presented to the emergency department with a deliberate overdose of 300 units of insulin aspart (Novorapid, Novo Nordisk, Copenhagen, Denmark). His venous blood glucose was 1.6 mmol/L (28 mg/dL) and serum insulin level was 452.3 mu/L (fasting reference range 3-15 mu/L) at admission.He was treated with dextrose infusion, glucagon injection, and 40% glucose gel over 9 hours with in-patient monitoring for 36 hours. At the end of day 7, the sensor was removed and data were downloaded. ResultSevere hypoglycemia was managed appropriately with parenteral and enteral glucose, and glucagon. Analysis of CGM data (Figure 1) showed failure of the sensor to detect hypoglycemia with the reported sensor glucose ranging between 5 and 6 mmol/L (90-108 mg/dL). While the mean absolute relative difference (MARD%) for the whole 7 days of CGM was 17.7%, it was 52% in the first 9 hours post-insulin overdose. DiscussionDespite clinical benefits of CGM and data suggesting continuous knowledge of glucose is a research priority, uptake is lower than may be expected. 2 This in part due to reimbursement challenges, discomfort, complexity, the need for calibration and the limited life span of sensors, but also reflects alarm fatigue related to sensor inaccuracy, particularly in the hypoglycemic range. For people who persevere with CGM despite these limitations, an increase in 579691D STXXX10.1177/1932296815579691Journal of Diabetes Science and TechnologyEl-Laboudi et al research-article2015

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