5 Hyperosmolar Hyperglycemic State

Recognizing HHS

Hyperosmolar hyperglycemic state (HHS) is a medical emergency requiring hospital treatment. It is marked by severe hyperglycemia, dehydration, and hyperosmolality, and may involve altered mental status with little or no significant ketoacidosis. Actual care should follow clinician direction and local protocols.

A presentation with several days of thirst and frequent urination followed by confusion, glucose of $\text{720 mg/dL}$, sodium of $\text{148 mmol/L}$, $\beta$-hydroxybutyrate of $\text{1.2 mmol/L}$, pH of $\text{7.36}$, and bicarbonate of $\text{21 mmol/L}$ is consistent with HHS: marked hyperglycemia and dehydration with minimal ketones and no substantial acidosis. HHS and diabetic ketoacidosis can overlap, so diagnosis depends on the full clinical and laboratory picture.

Assessing the patient

Early assessment should identify immediate instability and volume depletion. Check airway, breathing, circulation, vital signs, mental status, and hydration and perfusion; confusion or reduced consciousness makes delaying emergency assessment unsafe.

Useful early tests include blood glucose, electrolytes, renal function, ketones, and acid–base status using a venous blood gas. Assess serum osmolality and monitor urine output. The care team should also look for a precipitating cause based on the patient’s symptoms and findings.

Starting fluid replacement

Intravenous fluid replacement is a core early intervention. For adults without cardiac or renal compromise, initial treatment guidance describes isotonic saline or balanced crystalloid at $\text{500–1,000 mL/hour}$ during the first $\text{2–4 hours}$, adjusted to clinical status.

Older adults and people with heart or kidney disease may need smaller fluid boluses and more frequent reassessment to reduce the risk of fluid overload. Fluid management should be guided by the patient’s condition and repeated assessment.

Guiding insulin with potassium

Potassium must be assessed before insulin is started. Insulin can shift potassium into cells and worsen hypokalemia; if potassium is below $\text{3.5 mmol/L}$, replace potassium under a monitored protocol and defer insulin until potassium is above that threshold. Continue close monitoring and follow the treating team’s protocol.

Correcting and monitoring safely

Glucose and osmolality should be corrected gradually because rapid shifts in osmolality can be associated with neurologic complications. Guidance advises that glucose decline in HHS should generally not exceed $\text{90–120 mg/dL per hour}$, while osmolality should decline gradually.

As glucose falls, water shifts back into cells and measured sodium may rise. A rise by itself is not an automatic reason to switch to hypotonic fluid; clinicians consider hydration, overall fluid balance, and whether osmolality is declining appropriately.

Check bedside glucose every $\text{1–2 hours}$. Reassess vital signs, mental status, fluid balance, and urine output, and repeat electrolytes, renal function, and serum osmolality about every $\text{4 hours}$ initially. Monitor for hypoglycemia, potassium abnormalities, fluid overload, worsening kidney function, and changes in neurologic status.

Investigating the precipitating cause

After initial stabilization, investigate and treat the illness or event that precipitated HHS, in addition to managing dehydration and hyperglycemia. Examples include infection, such as pneumonia or urinary infection; myocardial infarction; stroke; and missed or insufficient diabetes medication. The specific evaluation depends on the patient’s symptoms and findings.