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Diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) encompass two severe complications of diabetes mellitus (DM). The incidence is increasing in the United States, with 120,000 hospitalizations for DKA in 2005, which was a 20% increase compared with 2000.1 Of the hospitalizations for DKA in 2005, 72% were 44 years old or younger, 21% were between 45 and 64 years old, and <1% were 65 years old or older.1 Although the rate of hospitalizations for DKA continues to rise, mortality from DKA has been declining, and in 2005 mortality was 0.8 deaths per 100,000.1 HHS, on the other hand, has a lower rate of hospitalization but a higher mortality at a rate of 5–20%.2,3 The cost of DKA is profound and the aggregate cost of its hospitalizations is approximately $850 million.4
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DKA is defined by the following criteria (Table 31-1): plasma glucose >250 mg/dL, arterial pH ≤7.30, serum bicarbonate ≤18 mEq/L, presence of urinary and serum ketones, and an anion gap >10 mEq/L.2 It is further divided into mild, moderate, and severe based on the degree of acidemia that corresponds to an arterial pH of 7.25–7.30, 7.00 to <7.24, and <7.00, respectively, or a serum bicarbonate level of 15–18, 10 to <15, and <10 mEq/L, respectively.2 HHS is defined by the following criteria: plasma glucose >600 mg/dL, an arterial pH >7.30, serum bicarbonate >18 mEq/L, an effective serum osmolality >320 mOsm/kg (where effective serum osmolality = 2[measured Na+ (mEq/L)] + glucose [mg/dL]/18).2,5 Although HHS was previously called hyperglycemic hyperosmolar nonketotic state (HHNKS), small urinary and serum ketones may be seen in this condition and thus their presence does not exclude the diagnosis of HHS.2 DKA and HHS in reality lie along a continuum, and up to 33% of patients may have a clinical presentation in which features of both are present in varying degrees.3
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Traditionally, DKA was thought to occur only in type 1 DM and HHS in type 2 DM. There is a newly recognized entity, however, of ketosis-prone type 2 DM.6 These patients present with DKA resulting from decreased insulin secretion and action but they characteristically recover β-islet cell function within a ...