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Chapter 33: Acid–Base Disorders

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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.

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

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a. Metabolic acidosis

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b. Metabolic alkalosis

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c. Respiratory acidosis

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d. Respiratory alkalosis

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

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

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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.

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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.

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Has the patient been appropriately compensated for the primary disorder?

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

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

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

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

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

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

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Answer d is incorrect. The patient ...

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