Hyperosmolar hyperglycemic [nonketotic] syndrome (HHS, aka hyperosmolar non-ketotic coma, HONK, nonketotic hyperosmolar coma) is a complication of diabetes mellitus (predominantly type 2), in which hyperglycemia (high blood sugars) cause severe dehydration, increases in osmolarity (relative concentration of solute), and a high risk of complications, coma and death.

• Dehydration
• Substantial thirst (polydipsia)
• Neurological Sx, including:
  • Focal sensory or motor impairments
  • Focal seizures
  • Motor abnormalities, including flaccidity, depressed reflexes, tremors, or fasciculations

• Blood tests, including:
  • Plasma glucose levels >30mmol/L
  • Serum osmolality >320 mOsm/kg
  • Serum pH>7.3
  • Bicarbonate >15 meQ/L
• Profound dehydration, up to an average of 9L
• Measurement of ketone bodies, to DDx from DKA, which are the underlying driver for DKA, but are usually NOT detectable in HONK, including:
  • Small ketones on dipstick
  • Absent-to-low ketonuria on urinalysis (<3mmol/L)

• IV fluids, to correct the dehydration
• Insulin, to reduce BSL's
• Mx of underlying conditions that may have precipitated the illness, e.g. an acute infection

• Hyperviscosity, and increased risk fo blood clot formation

• Diabetic ketoacidosis (DKA), another complication of diabetes, more often, but not exclusively, encountered in patients with T1DM