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Hyperosmolar hyperglycaemic state

Background knowledge ๐Ÿง 


  • Hyperosmolar hyperglycaemic state (HHS) is a serious complication of diabetes mellitus, characterized by severe hyperglycaemia, hyperosmolality, and dehydration without significant ketoacidosis.
  • Typically occurs in Type 2 diabetes.
  • Medical emergency requiring prompt treatment.


  • More common in elderly patients with Type 2 diabetes.
  • Incidence: approximately 1 per 1,000 person-years among diabetics.
  • Higher prevalence in those with concomitant illness or infection.
  • Mortality rate higher than diabetic ketoacidosis (DKA).

Aetiology and Pathophysiology

  • Relative insulin deficiency leading to hyperglycaemia.
  • Severe hyperglycaemia causes osmotic diuresis and dehydration.
  • Precipitating factors: infections, myocardial infarction, stroke, medications (e.g., steroids, diuretics).
  • Lack of significant ketosis due to some residual insulin activity.
  • High serum osmolality (>320 mOsm/kg) due to elevated glucose.

Clinical Features ๐ŸŒก๏ธ


  • Polyuria and polydipsia.
  • Profound dehydration.
  • Weakness and fatigue.
  • Nausea and vomiting.
  • Altered mental state: confusion, drowsiness, coma.
  • No significant ketonuria or ketonaemia.


  • Severe hyperglycaemia (glucose >30 mmol/L).
  • High serum osmolality (>320 mOsm/kg).
  • Dehydration: dry mucous membranes, reduced skin turgor.
  • Hypotension and tachycardia.
  • Neurological deficits due to hyperosmolality.
  • Absence of significant acidosis (pH >7.3, bicarbonate >15 mmol/L).

Investigations ๐Ÿงช


  • Blood glucose: markedly elevated (>30 mmol/L).
  • Serum osmolality: elevated (>320 mOsm/kg).
  • Electrolytes: sodium may be elevated or normal, potassium may be low.
  • Renal function tests: elevated urea and creatinine due to dehydration.
  • Venous blood gases: pH >7.3, bicarbonate >15 mmol/L, i.e. no significant acidosis.
  • Capillary ketones: no significant ketonaemia.
  • Infection screen: blood cultures, urine culture, chest X-ray.

Management ๐Ÿฅผ


  • Aggressive fluid replacement: intravenous 0.9% saline initially.
  • Insulin therapy: low-dose fixed rate infusion to gradually reduce blood glucose if not falling with fluids alone.
  • Electrolyte replacement: monitor and correct potassium, sodium.
  • Treat underlying cause: antibiotics for infections, management of precipitating factors.
  • Frequent monitoring: glucose, electrolytes, osmolality, vital signs.
  • Avoid rapid correction of hyperglycaemia and osmolality to prevent cerebral oedema.


  • Cerebral oedema.
  • Severe dehydration and hypovolemic shock.
  • Electrolyte imbalances (hypokalemia, hypernatremia).
  • Thromboembolism.
  • Acute kidney injury.
  • Infections due to immunosuppression.
  • Death if not promptly treated.


  • Mortality rate 10-20%, higher than DKA.
  • Prognosis depends on prompt recognition and treatment.
  • Early and aggressive management improves outcomes.
  • Long-term management includes strict glucose control and addressing precipitating factors.
  • Regular follow-up to prevent recurrence.

Key Points

  • HHS is a medical emergency requiring prompt treatment.
  • Characterized by severe hyperglycaemia, hyperosmolality, and dehydration.
  • Common in elderly patients with Type 2 diabetes.
  • Management focuses on fluid replacement, insulin therapy, and treating underlying causes.
  • Monitoring and gradual correction of glucose levels are crucial to avoid complications.
  • Prognosis depends on timely and effective treatment.

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