Chapter 33: Acid–Base Disorders

Chapter 33: Acid–Base Disorders

A 58-year-old woman is in the intensive care unit, intubated after a recent abdominal surgery. While in the operating room, she received more than 10 L of fluid and blood products, but has been aggressively diuresed since that time. In the past 3 days she has generated 8 L of urine output, her BUN and Cr have increased to 40 mg/dL and 1.5 mg/dL, respectively, and her blood pressure has decreased to 100/60 mm Hg. This morning, her ABG shows the following: pH 7.51, Paco₂ 46 mm Hg, and HCO₃ 35 mEq/L.

Which of the primary acid–base disturbances is present in this patient?

a. Metabolic acidosis

b. Metabolic alkalosis

c. Respiratory acidosis

d. Respiratory alkalosis

Answer b is correct. The pH is elevated, indicating alkalosis, and the bicarbonate is greater than 28, indicating metabolic alkalosis.

Answers a and c are incorrect. The pH is alkalemic; therefore, acidosis can be excluded.

Answer d is incorrect. The Paco₂ is greater than 40 mm Hg which would be inappropriate for a respiratory alkalosis. The patient has a metabolic alkalosis secondary to overdiuresis which has led to volume contraction.

A 58-year-old woman is in the intensive care unit, intubated after a recent abdominal surgery. While in the operating room, she received more than 10 L of fluid and blood products, but has been aggressively diuresed since that time. In the past 3 days she has generated 8 L of urine output, her BUN and Cr have increased to 40 mg/dL and 1.5 mg/dL, respectively, and her blood pressure has decreased to 100/60 mm Hg. This morning, her ABG shows the following: pH 7.51, Paco₂ 46 mm Hg, and HCO₃ 35 mEq/L.

Has the patient been appropriately compensated for the primary disorder?

a. Yes, the Paco₂ is elevated, indicating appropriate compensation.

b. Yes, the HCO₃ is elevated, indicating appropriate compensation.

c. No, the HCO₃ is low, indicating the patient has not yet been compensated.

d. No, the Paco₂ is low, indicating the patient has not yet been compensated.

Answer a is correct. In metabolic alkalosis we would expect the Paco₂ to be elevated as compensation to hold on to acid.

Answers b and c are incorrect. The patient does not have a primary respiratory problem.

Answer d is incorrect. The patient ...