Intravenous Insulin Resistance in a Critically Ill Patient Secondary to Decreased Peripheral Perfusion

Introduction: Intravenous (IV) insulin infusion is the preferred treatment modality for hyperglycemia in the intensive care unit (ICU) due to its short duration of action and easy titratability. However, administration of IV insulin has challenges. These include frequent monitoring, site infiltration, and high insulin dose requirements with other ICU medications such as epinephrine. There are, however, limited reports demonstrating an elevated insulin requirement due to poor peripheral perfusion. Below illustrates such a case, necessitating a change from peripheral to central IV insulin administration. Case Presentation: A 50 year old male with well controlled type 2 diabetes and previous aortic valve replacement presented to our facility for prosthetic valve endocarditis complicated by aortic root abscess. He was admitted to the ICU, treated with IV antibiotics, abscess washout and aortic valve replacement. Preoperatively, he was started on IV regular insulin via continuous infusion through a central line. During the pre and intraoperative periods, his hourly IV insulin requirement ranged from 2.4 to 5 units/ hour (hr). His blood glucose (BG) ranged from 107-251mg/dL (n 70-99mg/dL). The patient became hypotensive intraoperatively requiring vasopressor support. Dobutamine and norepinephrine infusions were started via central access and were continued postoperatively at steady rates. Vasopressin was added through central access as the patient failed to meet hemodynamic targets. Postoperatively, the propofol infusion was discontinued and the IV regular insulin infusion was moved to the peripheral line where the propofol had previously been administered. BG increased steadily to a maximum of 402 mg/dL despite an increase in the peripheral IV insulin rate to 152.4 units/hr. The site of the IV insulin drip was changed to another solitary peripheral access without success in decreasing the IV insulin infusion rate. The elevated requirements were deemed secondary to the patient’s lack of peripheral perfusion and should decrease with transition to a central line. A preemptive decrease in insulin drip rate to 10% of the peripheral dose was used to avoid hypoglycemia. The insulin drip was changed to a central access with a rate of 15units/ hr. BG values declined to a range of 140 -180 mg/dL. The patient remained on the multiple vasopressors for hemodynamic support, however, the insulin drip was able to be decreased and ultimately, discontinued. Conclusion: This case illustrates a unique challenge in the treatment of hyperglycemia with multifactorial shock and our approach to management. Elevated IV insulin requirements persisted despite stability in vasopressor dose, change to a solitary peripheral IV site, and lack of interfering medications in the treatment regimen. This is the first case to demonstrate a relationship between high IV insulin requirements and poor peripheral perfusion.