arise from events associated with hyperglycemia and insufficient insulin
Diabetic ketoacidosis (DKA), also referred to as diabetic acidosis and diabetic coma, is caused by a profound deficiency of insulin and is characterized by hyperglycemia, ketosis, acidosis, and dehydration. It is most likely to occur in people with type 1 diabetes but may be seen in type 2 in conditions of severe illness or stress when the pancreas cannot meet the extra demand for insulin. Precipitating factors include illness and infection, inadequate insulin dosage, undiagnosed type 1 diabetes, poor self-management, and neglect.
Hyperosmolar hyperglycemic syndrome (HHS) is a life-threatening syndrome that can occur in the patient with diabetes who is able to produce enough insulin to prevent DKA but not enough to prevent severe hyperglycemia, osmotic diuresis, and extracellular fluid depletion (Fig. 49-12). HHS is less common than DKA. It often occurs in patients over 60 years of age with type 2 diabetes. Common causes of HHS in a patient with type 2 diabetes are infections of the urinary tract, pneumonia, sepsis, any acute illness, and newly diagnosed type 2 diabetes. The main difference between HHS and DKA is that the patient with HHS usually has enough circulating insulin so that ketoacidosis does not occur.
Hypoglycemia, or low blood glucose, occurs when there is too much insulin in proportion to available glucose in the blood. This causes the blood glucose level to drop to less than 70 mg/dL (3.9 mmol/L). Once plasma glucose drops below 70 mg/dL (3.9 mmol/L), neuroendocrine hormones are released and the autonomic nervous system is activated. Suppression of insulin secretion and production of glucagon and epinephrine provide defense against hypoglycemia. Epinephrine release causes manifestations that include shakiness, palpitations, nervousness, diaphoresis, anxiety, hunger, and pallor. Because the brain requires a constant supply of glucose in sufficient quantities to function properly, hypoglycemia can affect mental functioning. These manifestations are difficulty speaking, visual disturbances, stupor, confusion, and coma. Manifestations of hypoglycemia can mimic alcohol intoxication. Untreated hypoglycemia can progress to loss of consciousness, seizures, coma, and death.
Hypoglycemic unawareness is a condition in which a person does not experience the warning signs and symptoms of hypoglycemia until the glucose levels reach a critical point. Then the person may become incoherent and combative or lose consciousness. This is often related to autonomic neuropathy of diabetes that interferes with the secretion of counterregulatory hormones that produce these symptoms. Elderly patients and patients who use β-adrenergic blockers are also at risk for hypoglycemic unawareness.