A 23-year-old man comes to the emergency department due to abdominal pain and nausea for the last few hours. He also reports an episode of vomiting and has noticed that his urine has a fruity odor. The patient has had increased thirst and urination for the past several days along with weight loss. He has no known medical problems and takes no medications. Physical examination reveals pallor with cool extremities. The abdomen is soft, without tenderness to palpation. Laboratory studies are ordered to confirm the diagnosis. Which of the following points on the graph below best corresponds to this patient's acid-base status?

Question

A 23-year-old man comes to the emergency department due to abdominal pain and nausea for the last few hours.  He also reports an episode of vomiting and has noticed that his urine has a fruity odor.  The patient has had increased thirst and urination for the past several days along with weight loss.  He has no known medical problems and takes no medications.  Physical examination reveals pallor with cool extremities.  The abdomen is soft, without tenderness to palpation.  Laboratory studies are ordered to confirm the diagnosis.  Which of the following points on the graph below best corresponds to this patient's acid-base status?

Quizplus · Accepted Answer

11ec160b_3cf0_8679_9249_bf258eb25229_MD0001_00 Diabetic ketoacidosis (DKA) is characterized by polydipsia, polyuria, and a fruity odor to the breath and/or urine. Patients frequently present with abdominal pain, nausea, and vomiting (as seen in this patient). Laboratory results reveal elevated anion gap metabolic acidosis secondary to accumulation of ketone bodies (eg, beta-hydroxybutyrate and acetoacetate); excreted acetone causes the fruity smell associated with DKA. Serum bicarbonate is used to buffer the excess ketoacids in the blood, so the bicarbonate level falls. Metabolic acidosis also stimulates ventilation by a chemoreceptor reflex that causes compensatory respiratory alkalosis, which lowers CO₂ partial pressure. The normal acid-base balance in a healthy individual is represented in the graph above by Point C (Choice C). An individual with DKA will have low blood pH, low serum HCO₃^-, and low PaCO₂ (Point E). (Choices A and B) Point B corresponds to a primary respiratory acidosis (low pH and high PaCO₂). Point A reflects chronic respiratory acidosis with compensatory metabolic alkalosis (renal retention of bicarbonate). (Choice D) Point D corresponds to a primary respiratory alkalosis as seen in hyperventilatory states (eg, pulmonary embolism, anxiety, high altitude). Educational objective: Diabetic ketoacidosis (DKA) is characterized by polydipsia, polyuria, and a fruity odor to the breath and/or urine. DKA is associated with elevated anion gap metabolic acidosis that is usually accompanied by compensatory respiratory alkalosis. This combination yields a low pH, low serum bicarbonate, and low PaCO₂.

A 23-Year-Old Man Comes to the Emergency Department Due to Abdominal