Why do patients with hyperosmolar hyperglycemic syndrome (non‑ketotic hyperglycemia) experience vomiting?

Why Patients with Hyperosmolar Hyperglycemic Syndrome Experience Vomiting

Vomiting in HHS patients occurs as part of the classical clinical presentation of severe hyperglycemia and hyperosmolarity, though it is less prominent than in diabetic ketoacidosis. 1

Pathophysiologic Mechanism

The vomiting in HHS results from the metabolic derangements caused by:

• Severe hyperglycemia and hyperosmolarity that develop over days to weeks, leading to profound dehydration and electrolyte disturbances 1
• Osmotic diuresis from glycosuria causing massive losses of water, sodium, potassium, and other electrolytes 1
• Gastric irritation and delayed gastric emptying secondary to the metabolic crisis and dehydration 1

Clinical Presentation Pattern

The classical clinical picture of HHS includes vomiting as one of several key symptoms:

• Polyuria, polydipsia, polyphagia, and weight loss precede the vomiting 1
• Vomiting occurs alongside dehydration, weakness, and altered mental status as the syndrome progresses 1
• The evolution is typically gradual (days to weeks), unlike DKA which develops more acutely 1

Important Clinical Distinctions

Vomiting is less severe in HHS compared to DKA:

• Up to 25% of DKA patients have significant emesis, which may be coffee-ground in appearance and guaiac positive due to hemorrhagic gastritis 1
• HHS patients can present with nausea and vomiting 2, 3, but this is not as prominent a feature as in DKA
• Abdominal pain is characteristic of DKA but NOT typically of HHS 1

Clinical Pitfalls to Avoid

• Do not assume vomiting rules out HHS - it can occur in both hyperglycemic crises 1
• Always investigate for precipitating causes - infection is the most common trigger, and vomiting may be related to the underlying illness rather than HHS itself 1, 4
• Consider mixed presentations - some patients may have features of both DKA and HHS 5
• Vomiting that persists after correction of dehydration and metabolic abnormalities requires further evaluation for other causes 1

Underlying Precipitants

When evaluating vomiting in HHS patients, search for:

• Infection (most common precipitating factor) 1
• Acute coronary syndrome, stroke, or pancreatitis 1, 4
• Medications affecting carbohydrate metabolism (corticosteroids, thiazides, sympathomimetics) 1