Hyperglycemic hyperosmolar nonketotic syndrome is a metabolic derangement that occurs principally in elderly patients with mild or undiagnosed type 2 diabetes. The complication is characterized by hyperglycemia, hyperosmolarity (thickening of the blood), with little if any ketosis. (In diabetic ketoacidosis, by comparison, there is high blood sugar, with massive buildup of acidic breakdown products called ketones.)

Most patients have severe dehydration and neurologic deficits when the diagnosis is made. Many times, the scenario involves an elderly person, perhaps in a nursing home, perhaps without a diagnosis of diabetes, who gradually deteriorates in mental function and becomes withdrawn, not taking sufficient fluids while continuing to urinate profusely until severe dehyration results. If unrecognized and untreated, the condition progresses to coma and death. Ordinarily, coma is present in only a small percentage of cases (less than 10%) at the time of diagnosis. If recognized early, and treated appropriately, recovery is anticipated. The survivor will now carry a diagnosis of type 2 diabetes and may no longer need insulin therapy after successful treatment of whatever underlying stress event triggered the dehydration.

Laboratory

• The blood glucose level in HHNS is often extremely high, frequently above 800 mg/dl [44 mmol/L].
• Both blood and urine ketones are absent (or, if present, are present only in small amounts).
• A lab test called osmolality is elevated. This test measures amount of particles in a solution (in this case, glucose in the blood).
• Blood pH is normal or only slightly decreased. (That is, blood acid level is either normal or only slightly elevated. Note: the pH level goes down when the acid level goes up.)