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Managing hyperosmolar syndrome

Diabetic hyperosmolar (nonketotic) syndrome (DHNS) is a complication of diabetes mellitus that is not commonly observed in the dog. However, hyperosmolar syndrome is a potentially serious development in diabetic ketoacidosis (DKA) and can have profound effects on the central nervous system function.


Physical examination often reveals profound dehydration, and the dog is typically lethargic, extremely depressed, or actually comatose. There is a direct relationship between the severity of the hyperosmolality and the severity of these signs.

Affected dogs also exhibit the classic signs of diabetes mellitus (polydipsia, polyuria, polyphagia, and weight loss). They progressively get weaker, experience anorexia, become lethargic, and drink less fluids.

Management guidelines

Goals of management include the correction of fluid deficits and electrolyte balance associated with severe dehydration, the reduction of blood glucose via insulin therapy, correction of the hyperosmolar state and management of concurrent diseases.

Hyperosmolality usually resolves with intravenous isotonic fluid and insulin therapy, although correction of the hyperosmolar state must be done slowly to minimize the shift of water from the extracellular to the intracellular compartment. Fluid therapy is critical to manage DHNS, especially in the first 4 to 6 hours of management.

The normal range of serum osmolality in a dog is typically 280 to 300 mOsm/kg.

The goal is to reduce blood glucose at the rate of 50 mg/dL/hr. When the blood glucose approaches 250 mg/dL, the IV fluid selection should be changed to 5% dextrose solution. Insulin therapy should be delayed (typically 4 to 6 hours) until the fluid therapy has improved the condition of the dog, and corrected the dehydration, improved the urine production, hyperglycemia, hyperosmolality and electrolytes. The need for insulin management is not as critical with hyperosmolar nonketotic syndrome as with ketoacidosis.

Evaluation of management

When evaluating the fluid therapy, it is important to consider several areas including urine monitoring, blood pressure, blood glucose, serum electrolytes, BUN, and urine glucose.