Introduction

• In contrast to diabetic ketoacidosis Diabetic ketoacidosis, which is a common complication of diabetes mellitus in dogs, hyperosmolar hyperglycemic state is a rare complication.
• Affected dogs typically present with severe hyperglycemia and dehydration.
• Differentiation of hyperosmolar hyperglycemic state from diabetic ketoacidosis might not be clinically relevant:
  • The term hyperosmolar hyperglycemic state is preferred over hyperosmolar non-ketotic diabetes because some degree of ketosis and acidosis may be present in this condition.
  • A mixed state of diabetic ketoacidosis and hyperosmolar hyperglycemic state is reported in about 30% of human patients presented for diabetic emergency. These data are not available for dogs, but the situation might be similar.
• Management is similar to that for diabetic ketoacidosis, but is crucial that plasma sodium and glucose concentrations are decreased slowly to minimize the risk of cerebral edema.

Pathogenesis

Etiology

• Absolute or relative insulin deficiency, combined with:
  • Any disease that causes severe fluid loss and dehydration.
  • Impaired renal excretion of glucose secondary to hypovolemia.

Predisposing factors

• Diabetes causes osmotic diuresis and compensatory polydipsia. Dehydration is inevitable if the dog cannot consume sufficient water to compensate for urinary loss.
• Additional fluid losses, eg due to acute pancreatitis Pancreatitis: acute or gastrointestinal disease, can then result in more severe dehydration:
  • Vomiting and diarrhea are the most common reasons for severe fluid loss.
• Pre-existing renal or cardiac disease can predispose to impaired renal function.

Pathophysiology

• Hypovolemia results in impaired renal function and prerenal azotemia Pre-renal azotemia.
• Urine output consequently decreases and so less glucose is excreted in urine. Blood glucose concentration then increases contributing to more severe hyperosmolality.
• Idiogenic osmoles are formed in the brain to protect the brain from fluid loss. Importantly, these idiogenic osmoles are cleared slowly once hyperosmolality is corrected, and so overly rapid lowering of plasma sodium and/or glucose can result in fluid shifting into the brain causing cerebral edema.

Diagnosis

Treatment

Outcomes