Hyperosmolar Hyperglycaemic State (HHS)

Question 1

what is hyperosmolar hyperglycaemic state (HHS)?

Answer 1

a life-threatening metabolic complication of T2DM characterised by severe hyperglycaemia, hyperosmolality, and dehydration, without significant ketoacidosis

Question 2

why are serum ketones not present in most patients with T2DM during hyperglycaemic crises?

Answer 2

• serum ketones are absent because insulin levels in most patients with T2DM are sufficient to suppress ketogenesis
• without acidosis symptoms, these patients experience prolonged osmotic diuresis, leading to severe dehydration before presentation
• as a result, plasma glucose levels (> 33.3 mmol/L) and osmolality (> 320 mOsm/L) are typically much higher than in DKA

Question 3

what is the pathophysiology of hyperosmolar hyperglycaemic state (HHS)?

Answer 3

• HHS develops due to severe hyperglycaemia (plasma glucose > 600 mg/dL) without significant ketoacidosis
• relative insulin deficiency prevents ketogenesis but is insufficient to suppress extreme hyperglycemia
• the high glucose concentration causes osmotic diuresis, leading to profound dehydration, electrolyte imbalances, and increased serum osmolality (> 320 mOsm/L)
• unlike DKA, acidosis is absent due to the presence of some insulin, which inhibits lipolysis and ketone production

Question 4

what are the symptoms of HHS?

Answer 4

• thirst
• polyuria
• dehydration (e.g. tachycardia, hypotension, dry mucous membranes, reduced skin turgor)
• nausea
• vomiting
• altered consciousness (e.g. confusion, coma)
• ? seizures

Question 5

what are the investigations for HHS?

Answer 5

• ABG/VBG
• FBC
• U&Es
• CRP
• LFTs
• serum glucose
• serum osmolarity
• capillary ketones/urine ketones
• BUN

Question 6

what are the three features that HHS is characterised by?

Answer 6

• profound hyperglycaemia (e.g. glucose >33.3mmol/L)
• hyperosmolality (e.g. serum osmolality >320mmol/kg)
• volume depletion in the absence of ketoacidosis (e.g. pH >7.3, HCO3 >15mmol/L)

Question 7

what is the emergency management of HHS?

Answer 7

• IV fluid (e.g. 1L 0.9% NaCl in 1 hour)
• fixed-rate intravenous insulin infusion (FRII) (e.g. 0.1 units/kg/hour)
• electrolyte replacement (e.g. IV potassium)

Question 8

what are the acute complications for HHS?

Answer 8

• dehydration
• thromboembolism
• AKI
• cardiovascular (e.g. arrhythmia)
• rhabdomyolysis