hyperosmolar non-ketotic hyperglycaemia

Last reviewed 10/2018

hyperglycemic hyperosmolar state (HHS)

Hperglycemic hyperosmolar state (HHS) previously known as hyperosmolar nonketotic (HONK) coma is a syndrome characterized by extreme elevations in serum glucose concentrations, hyperosmolality and dehydration without significant ketosis (1,2).

  • characteristic features that differentiate it from other hyperglycaemic states such as DKA are:
    • hypovolaemia
    • marked hyperglycaemia (30 mmol/L or more) without significant hyperketonaemia (7.3, bicarbonate >15 mmol/L)
    • osmolality usually 320 mosmol/kg or more
  • N.B. - a mixed picture of HHS and DKA may occur (2)

Incidence of HHS is unknown but is thought to be <1% of hospital admissions in patients with diabetes

  • it is common in elderly patients with type 2 diabetes, but HHS has also been reported in
    • children (in infants, especially those with 6q24-related transient neonatal diabetes mellitus )
    • young adults
    • in type 1 diabetes subjects
  • in children it is less frequent when compared to diabetic ketoacidosis (DKA)
  • mortality rate is estimated to be as high as 20% (10 times higher than in diabetic ketoacidosis) (1).

Gradually increasing polyuria and polydipsia will result in profound dehydration and electrolyte loss in a patient.

  • in adults with HHS, fluid loss is estimated to be twice as those with DKA
  • signs of dehydration may be less evident due to hypertonicity which preserves intravascular volume (1)

Osmolality can be calculated from the formula:

osmolality = 2(Na+K) + urea + glucose

Note that serum sodium may be low, despite the fact that the patient is severely hyperosmolar. This is due to the redistribution of fluid into the extracellular fluid (secondary to the high glucose level).