Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS, also known as nonketotic hyperglycemia) are two of the most serious acute complications of diabetes. They are part of the spectrum of hyperglycemia and each represents an extreme in the spectrum.
The clinical features and diagnosis of DKA and HHS will be reviewed here. The epidemiology, pathogenesis, and treatment of these disorders are discussed separately. (See "Epidemiology and pathogenesis of diabetic ketoacidosis and hyperosmolar hyperglycemic state" and "Treatment of diabetic ketoacidosis and hyperosmolar hyperglycemic state in adults".)
DKA and HHS differ clinically according to the presence of ketoacidosis and usually the degree of hyperglycemia [1-4]. The definitions proposed by the American Diabetes Association for DKA and HHS are shown in a table, along with criteria for classification of DKA as mild, moderate, or severe, based on the patient's arterial pH, serum bicarbonate, and mental status (table 1).
●In HHS, there is little or no ketoacid accumulation, the serum glucose concentration frequently exceeds 1000 mg/dL (56 mmol/L), the plasma osmolality may reach 380 mosmol/kg, and neurologic abnormalities are frequently present (including coma in 25 to 50 percent of cases) [2,3,5]. Most patients with HHS have an admission pH >7.30, a serum bicarbonate >20 meq/L, a serum glucose >600 mg/dL (33.3 mmol/L), and test negative for ketones in serum and urine, although mild ketonemia may be present.
●DKA is characterized by the triad of hyperglycemia, anion gap metabolic acidosis, and ketonemia. Metabolic acidosis is often the major finding. The serum glucose concentration is usually greater than 500 mg/dL (27.8 mmol/L) and less than 800 mg/dL (44.4 mmol/L) [2,6]. However, serum glucose concentrations may exceed 900 mg/dL (50 mmol/L) in patients with DKA who are comatose . In certain instances, such as DKA in the setting of starvation or pregnancy, or treatment with insulin prior to arrival in the emergency department, the glucose may be only mildly elevated. Factors that contribute to the lesser degree of hyperglycemia in DKA, compared with HHS, are discussed below. (See 'Serum glucose' below.)