CHAPTER 49 Diabetes Mellitus
1 Describe the principal types of diabetes mellitus
Type 1 diabetes mellitus: An autoimmune disorder in which destruction of the pancreatic islet cells results in the inability to produce insulin. Onset is more common in children and young adults.
Type 2 diabetes mellitus: A disorder in the body’s ability to use insulin. Early in the course of the disease the patient may be able to make sufficient insulin, but cell-receptor impairment results in hyperglycemia despite normal or high insulin levels. Type 2 diabetes is usually a disease of older adults; onset in the sixth decade and beyond is common. As obesity increases in the population type 2 diabetes also increases. Type 2 diabetes is now commonly seen in adolescents and young adults with obesity and a sedentary lifestyle.
2 What is considered ideal (target) glucose control?
The American Diabetes Association (ADA) 2008 Clinical Practice Recommendations recommend an A1C goal for nonpregnant adults in general of <7% (6% or lower is the nondiabetic A1C range). Less stringent goals apply to children, patients with a history of severe hypoglycemia, and individuals with comorbid conditions.
3 What comorbidities are frequently observed in patients with diabetes mellitus and to what significance?
Hypertension is seen in 40% of patients with poorly controlled diabetes who undergo surgery. Hypertension is a risk factor for coronary artery disease and cardiac failure. If these patients are treated with potassium-wasting diuretic agents, there is often significant total body loss of potassium.
Coronary artery disease is common, occurs in younger patients, and may be silent or present atypically.
Autonomic neuropathy may compromise neuroreflexic control of cardiovascular and gastrointestinal function, manifesting as orthostatic hypotension, gastroparesis (increased risk of aspiration), ileus, and urinary retention. Peripheral neuropathies are common.
Disturbances in renal function are common, including increased blood urea nitrogen (BUN) and creatinine, protein loss, hypoalbuminemia, acidosis, and electrolyte disturbances.
4 What oral medications are currently used in type 2 diabetes?
There are two categories of drugs used in treating type 2 diabetes: those that enhance the effectiveness of insulin and those that increase the supply of insulin to the cells. These drugs are outlined in Table 49-1.
5 What insulins are in current use?
Modern intensive insulin therapy relies on newly designed insulin analogs. Insulin therapy is given using a basal-bolus construct: long-acting (24-hour) insulin is used to provide a steady basal platform, and rapid-acting insulin is used to provide boluses for carbohydrate intake in meals and snacks. This necessitates giving at least four injections per day or the use of an insulin pump. The specific insulins are outlined in Table 49-1.
6 Is there an advantage to the use of insulins that are in solution as opposed to insulin that is in a suspension?
Insulins in solution provide exact dosing. For example, 10 units of Humalog will always be exactly 10 units. NPH, the only remaining insulin that is in suspension, does not provide exact or reproducible dosing, but varies by as much as 30% either way. Ten units of NPH could really be 7 to 13 units!
7 Describe the role of insulin on glucose metabolism and the impact of stress
Insulin enhances glucose uptake, glycogen storage, protein synthesis, amino-acid transport, and fat formation. Basal insulin secretion is essential even in the fasting state to maintain glucose homeostasis.
Surgical procedures lead to increased stress and high counterregulatory hormone activity with a decrease in insulin secretion. Counterregulatory hormones, including epinephrine, cortisol, glucagon, and growth hormone, promote glycogenolysis, gluconeogenesis, proteolysis, and lipolysis. Therefore, in diabetic patients without adequate insulin replacement, the combination of insulin deficiency and excessive counterregulatory hormones can result in severe hyperglycemia and diabetic ketoacidosis, which are associated with hyperosmolarity, increases in protein catabolism, fluid loss, and lipolysis.
8 Is there evidence that tight glucose control is beneficial in critically ill patients?
It has recently been believed that intensive insulin therapy to maintain glucose at or below 110 mg/dl reduces morbidity and mortality in critically ill patients in a surgical intensive care unit (ICU). However, it has subsequently been determined that extremely tight glucose control in surgical and medical ICUs significantly increases the risk of hypoglycemia and is not associated with significantly reduced hospital mortality. However, tight control does seem to significantly reduce septicemia and improve wound healing.
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