Diabetic ketoacidosis (DKA) results from a relative insulin deficiency and counter-regulatory hormone excess causing hyperglycemia and ketonemia. Table 129-3 lists causes.
Hyperglycemia causes an osmotic diuresis with dehydration, hypotension, and tachycardia. Ketonemia causes an acidosis with myocardial depression, vasodilation, and compensatory Kussmaul respiration. Nausea, vomiting, and abdominal pain are common. The absence of fever does not exclude infection. Acetone, formed from oxidation of ketone bodies, causes the characteristic fruity odor of the patient's breath.
Diagnosis and Differential
Diagnosis of DKA is based on clinical presentation and laboratory values of a glucose >250 milligrams/dL, bicarbonate <15 mEq/L, pH <7.3, and a moderate ketonemia.
An anion gap metabolic acidosis results from formation of ketonebodies. In DKA, the conversion of acetoacetate to β-hydroxybutyrate is favored. Therefore, the patient may have low levels of acetoacetate and high levels of β-hydroxybutyrate. If the nitroprusside test is used to detect serum or urine ketones, it may be falsely low or negative as it only detects acetoacetate, not β-hydroxybutyrate.
Osmotic diuresis results in loss of sodium, chloride, calcium, phosphorus, and magnesium, but initial serum levels may be normal from hemoconcentration. Serum and urine glucose and ketones are elevated. Pseudohyponatremia is common: for each 100 milligrams/dL increase in blood glucose, the sodium decreases by 1.6 mEq/L. Some recommend this sodium correction factor be 2.4, especially if the glucose is >400 milligrams/dL. Serum potassium may be low from osmotic diuresis and vomiting, normal, or high from acidosis. In acidosis, potassium is driven extracellularly. Therefore, the acidotic patient with normal or low potassium has marked depletion of total body potassium.
Laboratory investigation includes serum pH, glucose, electrolytes, blood urea nitrogen, creatinine, phosphorus, magnesium, complete blood count, urinalysis (and pregnancy if indicated), electrocardiogram, and chest radiograph to assess the severity of DKA and search for the underlying cause. When ordering serum pH, consider that venous pH correlates closely with arterial pH and avoid the pain and risk associated with arterial puncture.
The differential diagnosis includes other causes of an anion gap metabolic acidosis (Table 129-4). Hypoglycemia and hyperosmolar hyperglycemic state should also be considered.
Table 129-4 Differential Diagnosis for Diabetic Ketoacidosis |Favorite Table|Download (.pdf)
Table 129-4 Differential Diagnosis for Diabetic Ketoacidosis
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