Medical MCQ-A 26-year-old man is admitted through the casualty of the hospital for a heroin overdose. His hea rate is 45 beats/min, and his blood pressure is 75/40 mm Hg. Which of the following best depicts the results from an aerial blood sample?

A 26-year-old man is admitted through the casualty of the hospital for a heroin overdose. His hea rate is 45 beats/min, and his blood pressure is 75/40 mm Hg. Which of the following best depicts the results from an aerial blood sample?

pH 7.22, PaCO2 (mm Hg) 66, HCO3- (mEq/L) 26

pH 7.34, PaCO2 (mm Hg) 29, HCO3- (mEq/L) 15

pH 7.40, PaCO2 (mm Hg) 40, HCO3- (mEq/L) 24

pH 7.47, PaCO2 (mm Hg) 20, HCO3- (mEq/L) 14

Question Category:

Medicine

Correct Answer:

pH 7.22, PaCO2 (mm Hg) 66, HCO3- (mEq/L) 26

Description:

This man has a respiratory acidosis. Overdose with drugs that suppress ventilation (e.g., heroin, morphine, barbiturates, methaqualone, and "sleeping pills") often causes hypercapnia. In patients with an intact renal response, the respiratory acidosis causes a compensatory rise in plasma HCO3-, which lessens the fall in pH. However, the renal response requires several days to develop fully. The plasma HCO3- of 26 mEq/L (normal: 22-28 mEq/L) for this man is typical of acute respiratory acidosis with little or no renal compensation. pH 7.34, PaCO2 (mm Hg) 29, HCO3- (mEq/L) 15 reflects metabolic acidosis. pH 7.40, PaCO2 (mm Hg) 40, HCO3- (mEq/L) 24 is normal. pH 7.47, PaCO2 (mm Hg) 20, HCO3- (mEq/L) 14 reflects respiratory alkalosis.

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