A 45-year-old woman is evaluated in the emergency department for altered mental status.
On physical examination, the patient is tachypneic and obtunded. Temperature is normal, blood pressure is 94/64 mm Hg, pulse rate is 80/min, and respiration rate is 24/min.
Laboratory studies:
Electrolytes:
Sodium 133 mEq/L (133 mmol/L)
Potassium 3.9 mEq/L (3.9 mmol/L)
Chloride 110 mEq/L (110 mmol/L)
Bicarbonate 16 mEq/L (16 mmol/L)
Arterial blood gases:
pH 7.4
PCO2 27 mm Hg (3.6 kPa)