A 28-year-old man is found unresponsive in his bedroom by his roommate. Emergency medical services are called and he is brought to the hospital. He has a known past medical history of type 1 diabetes mellitus and major depressive disorder. On arrival, his temperature is 37.0°C (98.6°F), blood pressure is 105/65 mm Hg, pulse is 112/min, and respiratory rate is 12/min. Oxygen saturation is 92% on room air. Physical examination reveals a lethargic patient who only groans in response to sternal rub. His mucous membranes are notably dry. Pupillary examination reveals 2 mm pupils bilaterally that are sluggish to react to light.
Laboratory results are obtained:
| Serum Chemistry | Result | Reference Range |
|---|---|---|
| Sodium | 138 mEq/L | 136-145 mEq/L |
| Potassium | 4.5 mEq/L | 3.5-5.0 mEq/L |
| Chloride | 102 mEq/L | 95-105 mEq/L |
| Bicarbonate | 8 mEq/L | 22-28 mEq/L |
| Glucose | 520 mg/dL | 70-110 mg/dL |
| Arterial Blood Gas (Room Air) | Result | Reference Range |
|---|---|---|
| pH | 7.05 | 7.35-7.45 |
| 30 mm Hg | 35-45 mm Hg | |
| 65 mm Hg | 75-105 mm Hg |
Which of the following best describes this patient's acid-base status?
- Primary elevated anion gap metabolic acidosis and primary respiratory acidosisCevap
- BPrimary elevated anion gap metabolic acidosis and primary respiratory alkalosis
- CPrimary elevated anion gap metabolic acidosis with appropriate respiratory compensation
- DPrimary elevated anion gap metabolic acidosis and primary metabolic alkalosis
- EPrimary non-anion gap metabolic acidosis and primary respiratory acidosis
Cevap
The patient has a primary elevated anion gap metabolic acidosis and a concurrent primary respiratory acidosis.
The correct answer accurately identifies the presence of two primary acid-base disorders. The patient's presentation of acidemia (pH 7.05) with a low bicarbonate (8 mEq/L) defines a primary metabolic acidosis. The anion gap is calculated as mEq/L. Since this is greater than the normal value of 12 mEq/L, an elevated anion gap metabolic acidosis is present. To assess if the respiratory response is adequate, Winter's formula is used: Expected . For this patient, Expected mm Hg. The patient's actual is 30 mm Hg, which is significantly higher than the expected range of 18-22 mm Hg. When actual exceeds the expected , it signifies inadequate ventilation and a superimposed primary respiratory acidosis. Clinically, this patient has diabetic ketoacidosis (causing the high anion gap metabolic acidosis) complicated by an opiate overdose (evidenced by lethargy, 2 mm pupils, and a relative bradypnea of 12/min instead of the expected Kussmaul respirations), which is causing the concurrent respiratory acidosis.
Adım Adım Çözüm
Anahtar Kavram
In mixed acid-base disorders, Winter's formula must be used to evaluate if respiratory compensation is appropriate; an actual PaCO2 higher than the calculated expected value indicates a concurrent primary respiratory acidosis.