A 27-year-old woman is admitted to the hospital with a 4-day history of severe, frequent, watery diarrhea and diffuse abdominal pain. She has a history of ulcerative colitis and takes oral mesalamine. Her temperature is (), blood pressure is mm Hg, pulse is 118/min, and respirations are 26/min. The patient appears acutely ill, diaphoretic, and in moderate distress due to abdominal cramping.
Laboratory studies show:
| Test | Value |
|---|---|
| Serum sodium | 138 mEq/L |
| Serum potassium | 3.2 mEq/L |
| Serum chloride | 118 mEq/L |
| Serum bicarbonate | 10 mEq/L |
| Blood urea nitrogen | 32 mg/dL |
| Serum creatinine | 1.4 mg/dL |
Arterial blood gas analysis on room air:
| Test | Value |
|---|---|
| pH | 7.37 |
| PaCO2 | 18 mm Hg |
| PaO2 | 95 mm Hg |
Based on the laboratory results, which of the following best describes this patient's acid-base status?
- Mixed normal anion gap metabolic acidosis and respiratory alkalosisCevap
- BNormal anion gap metabolic acidosis with appropriate respiratory compensation
- CMixed high anion gap metabolic acidosis and respiratory alkalosis
- DHigh anion gap metabolic acidosis with appropriate respiratory compensation
- EPrimary respiratory alkalosis with appropriate metabolic compensation
Cevap
Mixed normal anion gap metabolic acidosis and respiratory alkalosis
The patient's arterial blood gas shows an acidemic pH of 7.37. The presence of a low serum bicarbonate ( mEq/L) identifies the primary disorder as a metabolic acidosis. The anion gap is calculated as , which is mEq/L. Since this falls within the normal range of 8 to 12 mEq/L, she has a normal anion gap metabolic acidosis, which is expected given her significant gastrointestinal bicarbonate loss from severe diarrhea.
To evaluate respiratory compensation, Winter's formula is applied: Expected . For this patient, the expected mm Hg (range: 21 to 25 mm Hg). The measured is mm Hg, which is significantly lower than the expected range. This indicates an excessive respiratory drive and the presence of a concomitant, independent primary respiratory alkalosis, likely secondary to fever, pain, and systemic inflammation from her acute ulcerative colitis flare.
To evaluate respiratory compensation, Winter's formula is applied: Expected . For this patient, the expected mm Hg (range: 21 to 25 mm Hg). The measured is mm Hg, which is significantly lower than the expected range. This indicates an excessive respiratory drive and the presence of a concomitant, independent primary respiratory alkalosis, likely secondary to fever, pain, and systemic inflammation from her acute ulcerative colitis flare.
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Anahtar Kavram
Patients with mixed acid-base disorders require stepwise calculation of the anion gap and application of Winter's formula to uncover concomitant primary disturbances that alter expected compensatory mechanisms.