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Chapter 36. Acid–Base Disorders
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A 35-year-old woman is in the intensive care unit, intubated after a recent abdominal surgery. While in the operating room, she received more than 8 L of fluid and blood products, but has been aggressively diuresed since that time. In the past 3 days she has generated 6 L of urine output, her blood urea nitrogen (BUN) and creatinine (Cr) have increased to 35 mg/dL and 1.4 mg/dL, respectively (baseline of 10 mg/dL and 0.7 mg/dL), and her blood pressure has decreased to 100/60 mm Hg. This morning, her arterial blood gas (ABG) shows the following: pH 7.50, PaCO2 48 mm Hg and HCO3 37 mEq/L. Which of the primary acid–base disturbances is present in this patient?
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Answer b is correct. The pH is elevated, indicating alkalosis, and the bicarbonate is more 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 above 40 mm Hg which would be inappropriate for a respiratory alkalosis. The patient has a metabolic alkalosis secondary to over-diuresis which has led to volume contraction.
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A 35-year-old woman is in the intensive care unit, intubated after a recent abdominal surgery. While in the operating room, she received more than 8 L of fluid and blood products, but has been aggressively diuresed since that time. In the past 3 days she has generated 6 L of urine output, her blood urea nitrogen (BUN) and creatinine (Cr) have increased to 35 mg/dL and 1.4 mg/dL, respectively (baseline of 10 mg/dL and 0.7 mg/dL), and her blood pressure has decreased to 100/60 mm Hg. This morning, her arterial blood gas (ABG) shows the following: pH 7.50, PaCO2 48 mm Hg, and HCO3 37 mEq/L.
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Has the patient 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 ...