Excerpt from Hyperosmolar Hyperglycemic Nonketotic Coma


Synonyms, Key Words, and Related Terms: HHNC, hyperosmolar coma, diabetic nonketotic coma, hyperosmolar nonketotic state, diabetic hyperosmolarity, diabetes, hyperglycemia, diabetic ketoacidosis, DKA, adult-onset diabetes, dehydration, sepsis, pneumonia, urinary tract infection, UTI, diuretics, beta-blockers, histamine 2 blockers, H2 blockers, stroke, intracranial hemorrhage, acute myocardial infarction, acute MI, acute heart attack, dialysis, gastrointestinal hemorrhage, hyponatremia

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Background: Hyperosmolar hyperglycemic nonketotic coma (HHNC) is a metabolic derangement that occurs principally in patients with adult-onset diabetes. The condition is characterized by hyperglycemia, hyperosmolarity, and an absence of significant ketosis.

Despite the name, coma is present in fewer than 10% of cases. Most patients present with severe dehydration and focal or global neurologic deficits. In many cases, the clinical features of HHNC and diabetic ketoacidosis (DKA) overlap and are observed simultaneously.

Pathophysiology: HHNC most commonly develops in patients with diabetes who have some concomitant illness that leads to a reduced fluid intake. Infection is the most common cause, but many other conditions can cause altered mentation and/or dehydration. Frequently, this concomitant illness is not identifiable.

Hyperglycemia and hyperosmolarity lead to osmotic diuresis and an osmotic shift of fluid to the intravascular space, resulting in further intracellular dehydration.

Unlike patients with DKA, patients with HHNC do not develop ketoacidosis, but the reason for this is not known. Contributing factors include the limitation on ketogenesis by hyperosmolarity, the lower levels of free fatty acids available for ketogenesis, the availability of insulin in amounts sufficient to inhibit ketogenesis but not sufficient to prevent hyperglycemia, and the hepatic resistance to glucagon in these patients.

Frequency:

  • In the US: The incidence is 17.5 cases per 100,000 people. This incidence is slightly higher than the incidence of DKA.

Mortality/Morbidity: The mortality rate is high (10-20%).

Sex: The prevalence is slightly higher in females than in males.

Age:

  • HHNC has a mean age of onset early in the seventh decade of life.
  • In contrast, the mean age for DKA is early in the fourth decade of life.
  • Residents of nursing facilities who are elderly and demented are at the highest risk, but the syndrome has been reported in patients as young as 18 months.Please click here to view the full topic text: Hyperosmolar Hyperglycemic Nonketotic Coma