A 34-year-old man is admitted to the hospital after sustaining a head injury and fractures of both femurs in a motor vehicle collision. CT scan of the head reveals a left-sided extradural hematoma. He has no history of chronic illness and takes no medications. The patient receives intravenous fluid boluses and blood transfusions and is taken to the operating room for fracture repair and removal of the hematoma. On the first postoperative day, laboratory results show high plasma glucose and lactate levels. Which of the following is the primary contributor to this patient's elevated blood glucose levels?

Question

A 34-year-old man is admitted to the hospital after sustaining a head injury and fractures of both femurs in a motor vehicle collision.  CT scan of the head reveals a left-sided extradural hematoma.  He has no history of chronic illness and takes no medications.  The patient receives intravenous fluid boluses and blood transfusions and is taken to the operating room for fracture repair and removal of the hematoma.  On the first postoperative day, laboratory results show high plasma glucose and lactate levels.  Which of the following is the primary contributor to this patient's elevated blood glucose levels?

Quizplus · Accepted Answer

11ec160b_36c8_c072_9249_41ca7c63f084_MD0001_00 Stress hyperglycemia is a transiently elevated blood glucose level in the context of severe illness in patients without preexisting diabetes mellitus. It is common in the intensive care unit and is typically seen in those with sepsis and other severe infections, burns, trauma, or major hemorrhage. Severe metabolic stress is associated with increased production of cortisol, catecholamines (primarily epinephrine and norepinephrine), glucagon, and proinflammatory cytokines (eg, IL-1, IL-6, tumor necrosis factor-alpha). Cortisol, catecholamines, and glucagon act on the liver to increase glycogenolysis and gluconeogenesis, stimulating release of glucose from the liver into the blood. In addition, the release of proinflammatory cytokines is associated with increased expression of glucose transporter (GLUT) 1 in the CNS and macrophages, along with decreased expression of GLUT4 (which mediates insulin-induced glucose uptake in peripheral tissues). This facilitates increased glucose uptake by the brain and immune cells responsible for fighting infection. (Choice A) During trauma resuscitation, most patients are given isotonic fluids (eg, normal saline, Ringer lactate), which are unlikely to cause hyperglycemia. Even if mild fluid-induced hyperglycemia occurs, blood glucose levels typically normalize quickly after fluid boluses. (Choice B) Norepinephrine stimulates peripheral lipolysis, releasing glycerol, which can be taken up by the liver for use in gluconeogenesis. Therefore, stress increases, not decreases, the hepatic glycerol supply. (Choice C) Severe illness is often associated with increased anaerobic glycolysis due to systemic or local tissue hypoxia (blood loss in this patient). Increased conversion of glucose to lactate in ischemic tissues raises plasma lactate levels. Glucose levels are often concurrently elevated due to stress hyperglycemia, but anaerobic glycolysis itself depletes glucose. (Choice E) The renal cortex can convert lactate to glucose via gluconeogenesis. However, it makes a significantly smaller contribution to circulating glucose levels than hepatic gluconeogenesis. Educational objective: Stress hyperglycemia is transiently elevated blood glucose levels in the context of severe illness (eg, sepsis, burns, major hemorrhage) in patients without preexisting diabetes mellitus. Cortisol and catecholamines released in response to severe metabolic stress act on the liver to increase glycogenolysis and gluconeogenesis. __________ References: Stress hyperglycemia: an essential survival response! (http://www.ncbi.nlm.nih.gov/pubmed/23470218)

A 34-Year-Old Man Is Admitted to the Hospital After Sustaining