Hyperglycemia causes an osmotic diuresis that may result in dehydration.
Patients with diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar state (HHS) are treated with intravenous fluids and insulin. Potassium supplementation should begin as soon as the potassium level is in the normal range.
Both DKA and HHS are often precipitated by another illness, frequently infection. An attempt should be made to search for and treat any precipitating illness.
When treating patients with HHS, it is important to follow sodium and serum osmolality measurements to document return to normal values.
Diabetes mellitus is a common disorder and is present in 6% of the population in the United States. Diabetes mellitus is defined as fasting blood glucose >126 mg/dL on 2 separate occasions or a random glucose >200 mg/dL plus the classic symptoms of hyperglycemia (ie, polyuria, polydipsia). Derangement of glucose homeostasis is a continuum that ranges from hypoglycemia on one extreme to diabetic ketoacidosis (DKA) on the other end of the spectrum.
Hyperglycemia, even in the absence of DKA or hyperglycemic hyperosmolar state (HHS), has many deleterious effects. An osmotic diuresis occurs when an elevated glucose level overwhelms the kidneys and begins to pull electrolytes and water into the urine. In the healthy individual, serum glucose of 240 mg/dL is required before glucose is found in the urine. Additionally, hyperglycemia impairs leukocyte function and wound healing, making patients prone to infection. Chronic hyperglycemia causes renal failure, blindness, neuropathy, and atherosclerosis.
Diabetic ketosis is an intermediate metabolic state between hyperglycemia and ketoacidosis. Patients have an inadequate amount of insulin to provide the necessary energy substrates to the cell. As a result, lipolysis is stimulated to provide ketone bodies that can be used as substrates by the brain and other tissues. The ketone bodies include acetoacetate, acetone, and β-hydroxybutyrate.
DKA is defined as blood glucose >250 mg/dL, serum bicarbonate <15 mEq/L, ketonemia, and an arterial pH <7.3. DKA is present in 5–10% of hospitalized patients. It is the presenting illness of diabetes mellitus in 15–25% of patients. When making the diagnosis of DKA, the physician should attempt to determine what has precipitated the illness. The most common causes of DKA are the “3 I's”: insulin lack, ischemia (cardiac), and infection. The mortality rate of patients with DKA is approximately 5% and most often is attributable to concomitant illness.
In DKA, reduced circulatory insulin levels do not allow glucose to reach the intracellular space. In response, the cell stimulates lipolysis, which provides the body with glycerol (substrate for gluconeogenesis) and free fatty acids. Free fatty acids are a precursor to the ketoacids, acetoacetate, acetone, and β-hydroxybutyrate. The ketone bodies can be used as an energy source, but when they are present in excess, metabolic acidosis results.
HHS occurs when a hyperglycemic osmotic diuresis causes extreme dehydration. Defining features include a serum glucose >600 mg/dL, plasma osmolality >320 mOsm/L, and the absence of ketoacidosis. HHS is most common in elderly individuals. It results in >1% of diabetes-related hospital admissions, but has a reported mortality rate of 20–60%. HHS occurs when a prolonged osmotic diuresis from hyperglycemia results in severe dehydration and an elevated serum osmolality. Concurrent medical illness is very common and is often a precipitating cause of HHS.