Nonketotic hyperosmolar coma (nonketotic hyperglycaemia) is a type of diabetic coma associated with a high mortality seen in diabetes mellitus type 2. The preferred term used by the American Diabetes Association is hyperosmolar nonketotic state (HNS). Other commonly used names are hyperosmolar hyperglycemic nonketotic coma (HHNKC)^[1] or hyperosmotic non-ketotic acidosis (HONK).

Pathophysiology

Nonketotic coma is usually precipitated by an infection,^[2] myocardial infarction, stroke or another acute illness. A relative insulin deficiency leads to a serum glucose that is usually higher than 33 mmol/l (600 mg/dl), and a resulting serum osmolarity that is greater than 350 mOsm. This leads to polyuria (an osmotic diuresis), which, in turn, leads to volume depletion and hemoconcentration that causes a further increase in blood glucose level. Ketosis is absent because the presence of some insulin inhibits lipolysis, unlike diabetic ketoacidosis.

Clinical presentation

The increasing hemoconcentration and volume depletion may result in:

• Hyperviscosity and increased risk of thrombosis,
• Disordered mental functioning,
• Neurologic signs including focal signs such as sensory or motor impairments or focal seizures or motor abnormalities, including flacidity, depressed reflexes, tremors or fasciculations,
• Ultimately, if untreated, will lead to death.

Treatment

The treatment involves slow hydration, replacement of electrolytes and intravenous insulin. Anticoagulants (such as low molecular weight heparins) are often commenced as there is a significant rate of thrombosis in patients with NKHC.

References

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