Posted: July 24th, 2017

A 75-year-old man has had increasing shortness of breath with exertion during the past 2 weeks. He has a 25-year history of hypertension well controlled with diuretics. Two months ago, serum urea nitrogen and creatinine concentrations were within the reference ranges. His pulse is 98/min, respirations are 19/min, and blood pressure is 180/100 mm Hg. The lungs are dull to percussion at the bases, and crackles are heard one-third of the way up bilaterally. Cardiac examination shows increased jugular venous pressure, an S3 gallop, and no murmur.

A 75-year-old man has had increasing shortness
of breath with exertion during the past 2 weeks.
He has a 25-year history of hypertension well
controlled with diuretics. Two months ago,
serum urea nitrogen and creatinine
concentrations were within the reference ranges.
His pulse is 98/min, respirations are 19/min, and
blood pressure is 180/100 mm Hg. The lungs are
dull to percussion at the bases, and crackles are
heard one-third of the way up bilaterally. Cardiac
examination shows increased jugular venous
pressure, an S3 gallop, and no murmur. There is
3+ pitting edema of the lower extremities. Serum
studies show:
Na+
126 mEq/L
K
+
5.4 mEq/L
Cl−
108 mEq/L
HCO3
−
16 mEq/L
Urea nitrogen 75 mg/dL
Creatinine 3 mg/dL
This patient most likely has which of the
following types of acid-base disturbance?
(A) Metabolic acidosis
(B) Metabolic alkalosis
(C) Respiratory acidosis
(D) Respiratory alkalosis