HHS - severe hyperglycaemia develops without significant ketosis, is the characteristic metabolic emergency of uncontrolled type 2 diabetes

HHS is a medical emergency which is extremely difficult to manage and has a significant associated mortality. Hyperglycaemia results in:

• osmotic diuresis
• severe dehydration
• electrolyte deficiencies.

Important to differentiate from DKA as management is different (Insulin can lead to adverse outcomes in HHS)

Whilst DKA presents within hours of onset, HHS comes on over many days, and consequently the dehydration and metabolic disturbances are more extreme - dehydration is therefore also corrected lower in HHS to avoid rapid fluid shifts

Epidemiology:

HHS typically presents in the elderly with type 2 diabetes mellitus (T2DM), however the incidence in younger adults is increasing. It can be the initial presentation of T2DM.

Pathophysiology

• hyperglycaemia → ↑ serum osmolality → osmotic diuresis → severe volume depletion
• Despite these severe electrolyte losses and total body volume depletion, the typical patient with HHS, may not look as dehydrated as they are, because hypertonicity leads to preservation of intravascular volume.

Precipitating factors:

• consumption of glucose-rich fluids
• concurrent medication such as thiazide diuretics or steroids
• intercurrent illness