A75-year-old woman is taken to the emergency room after ingesting 50 tablets of enteric-coated aspirin. She has chronic osteoarthritis and T2DM. On examination, temp 37.8 C. HR 135/min, RR 28/min, and BP 105/65 mmHg. Blood tests reveal serum sodium 147 meq/L, potassium 2.9 meg/L, chloride 100 meq/L, and glucose 170 mg/dl. Arterial blood gases show pH 7,29, PCO2 27 mmHg and HCO3 16 meg/L. Which of the following best describes her acid-base status?
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الإجابة: A. Metabolic acidosis with respiratory alkalosis
HCO3 16 → metabolic acidosis (AG = 147 − 116 = 31, high). Winter: expected PCO2 = 1.5 × 16 + 8 = 32 ± 2; actual 27 is lower → an additional primary respiratory alkalosis. This mixed picture is classic for salicylate overdose. 'Pure metabolic acidosis' (D) ignores the overbreathing.
ليش كل خيار صح أو غلط
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A
ليش صح
Salicylate overdose causes both a primary metabolic acidosis and a primary respiratory alkalosis, which is her picture (HCO3 16 with PCO2 27, below the Winter-expected 32 ± 2).
✓ Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 3 -
B
ليش غلط
Respiratory acidosis would need an actual PaCO2 higher than the Winter-predicted value; hers (27) is lower than the expected 32 ± 2.
✓ Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 6 -
C
ليش غلط
A low HCO3 suggests metabolic acidosis (or compensation for respiratory alkalosis); metabolic alkalosis needs an elevated HCO3, and hers is 16.
✓ Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 5 -
D
ليش غلط
A pure (simple) metabolic acidosis needs PaCO2 within the predicted range (32 ± 2); her PaCO2 of 27 is below it, so she is overbreathing.
✓ Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 6
- المصدر
- Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 3
Step Up To Medicine 6th Edition 2024 (Acid-base imbalance).pdf · p. 6 - المحاضرة
- Respiratory Failure & Acid–Base · Pulmonology · Module B
- ظهر في
- Respi bank