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A 45-year-old man with a history of poorly-controlled diabetes mellitus is admitted to the hospital for observation. The patient reports having increased thirst, polydipsia, and polyuria throughout the morning, followed by episodes of nausea and vomiting, as well as fatigue and general weakness. On admission, he is ill-appearing with dry skin and mucous membranes. His vital signs are significant for a heart rate near 110/min and a respiratory rate of 25/min. His breath smells similar to nail-polish remover. An arterial blood gas reveals the followng results:
Arterial CO2 29 Arterial pH:7.34 Arterial HC03 :29
Which of the following measurements would most likely be decreased in this patient?
OA. Plasma acetone
0 B.Plasma catecholamines
0 C.Plasma glucagon
OD. Ratio of acetoacetate to B-hydroxybutyrate
O E. Ratio of B-hydroxybutyrate to acetoacetate
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The correct answer is D. This patient's blood gases reveal a metabolic acidosis (low pH,
low HCO3 ). The decrease in arterial CO2 , resulting from increased breathing rate, is an
appropriate compensatory response to the acidosis. The smell of acetone (which is the
primary solvent of nail polish) on the breath of a diabetic suggests ketoacidosis in diabetes leads overproduction of ketoacids and high level of plasma acetone. Because acetone is highly volatile, it is excreted mainly by the
lungs. Ketoacids, which include acetoacetate and b-hydroxybutyrate, are normally produced
in roughly equal amounts. However, in pathologic conditions such as diabetes and
alcoholism, the ratio shifts to b-hydroxybutyrate predominating. Therefore, the ratio of
acetoacetate to b-hydroxybutyrate actually decreases, while the net amount of ketoacids
increases. Common causes of ketoacidosis include infection, missed insulin treatments,
myocardial infarction, cerebrovascular accident, or stress/trauma.
Plasma levels of acetone (choice A) are actually increased during ketosis, which lead to
the smell of nail polish remover on the patient's breath.
Plasma catecholamines (choice B) as well as glucagon (choice C) are increased during
ketoacidosis due to a shift in the metabolism to a starvation state.
The ratio of b-hydroxybutyrate to acetoacetate (choice E) is increased during diabetic
ketoacidosis due to the predominance of b-hydroxybutyrate production during this
pathologic process.
