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Chapter 1: Acid–Base Disorders

A 45-year-old male painter with past medical history of drug abuse presents to the emergency department with slurred speech and difficulty walking. His symptoms came on when he was on the job painting in the basement of a house.

  • Vital signs: BP 88/43 mmHg, RR 26 breaths/min, HR 100 beats/min, Temp 99°F

  • Lethargic but arousable with diffuse muscle weakness

  • Dry mucous membranes

  • Lungs clear

  • Regular rate and rhythm, no murmurs

  • Abdomen soft and nontender

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WBC 15 × 103/μL
Hgb 14.2 g/dL
Plt 312 × 103 μL
Sodium 136 mEq/L
Potassium 2 mEq/L
Chloride 118 mEq/L
CO2 12 mEq/L
BUN 52 mg/dL
Creatinine 1.5 mg/dL
Phosphorus 3 mg/dL
Plasma osmolality 280 mOsm/kg H2O
pH 6
EtOH Negative
Toxicity screen:
Marijuana +
Benzodiazepine +
Arterial Blood Gas:
pH 7.29
Pco2 26 mmHg

What is the most likely cause of the patient’s clinical condition?

A. Methanol ingestion

B. Toluene inhalation

C. Aspirin overdose

D. Alprazolam overdose

B. Toluene inhalation

Toluene is widely used in many industrial solvents, acrylic paints, and paint thinners. Toxicity may be a result of environmental, accidental, or intentional exposure. It is the most widely abused inhaled volatile drug; it causes a euphoric effect when sniffed. Toluene is metabolized to benzoic acid and then to hippuric acid. These anions are very readily excreted into the urine as sodium and potassium salts. Most patients with toluene ingestion present with hypovolemia, hypokalemia, and a normal anion gap acidosis.

Methanol ingestion (and frequently ethanol) would cause a high anion gap acidosis (choice A). Aspirin overdose causes a mixed respiratory alkalosis with high anion gap acidosis (choice C). Benzodiazepine overdose typically presents with a respiratory acidosis due to suppression of respiratory drive (choice D).

A 37-year-old woman with history of diabetes and alcohol abuse presents in unresponsive state to the emergency department. According to her son, she complained of blurred vision before losing consciousness.

Home medications: metformin

  • Vital signs: BP 99/43 mmHg, RR 26 breaths/min, HR 107 beats/min, Temp 98.4°F

  • Somnolent

  • Dry mucous membranes

  • Lungs clear

  • Tachycardic, no murmurs

  • Abdomen soft and nontender

  • No edema, cyanosis, or clubbing

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Arterial Blood Gas:
pH 6.724
Pco2 20 mmHg
BUN 56 mg/dL
Creatinine 2.4 mg/dL
Sodium 134 mEq/L
Potassium 5.2 mEq/L

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