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?
**Core Concept**
The patient is experiencing a heroin overdose, which can lead to respiratory depression, resulting in hypoxia and subsequent metabolic acidosis. This condition is characterized by an elevated anion gap due to the accumulation of acidic substances, such as lactic acid.
**Why the Correct Answer is Right**
The patient's heroin overdose has caused respiratory depression, leading to a decrease in oxygenation and an increase in carbon dioxide levels. This results in a decrease in pH, indicating acidosis. The elevated PaCO2 (66 mm Hg) is consistent with hyperventilation, which is a compensatory mechanism for the metabolic acidosis. The elevated HCO3- (26 mEq/L) is a sign of the body's attempt to compensate for the acidosis by increasing bicarbonate levels. The anion gap is likely elevated due to the accumulation of acidic substances such as lactic acid.
**Why Each Wrong Option is Incorrect**
**Option B:** This option shows a normal pH and PaCO2, but a low HCO3-, which is not consistent with the expected compensatory response to metabolic acidosis.
**Option C:** This option shows a normal pH and PaCO2, but an elevated HCO3-, which is not consistent with the expected compensatory response to metabolic acidosis.
**Option D:** This option shows an elevated pH and a low PaCO2, which is not consistent with the expected findings in a patient with heroin overdose-induced metabolic acidosis.
**Clinical Pearl / High-Yield Fact**
In patients with heroin overdose, it is essential to monitor for signs of respiratory depression and to provide supportive care, including oxygen therapy and cardiac monitoring. Additionally, naloxone should be administered promptly to reverse the effects of the overdose.
**✓ Correct Answer: A. pH 7.22, PaCO2 (mm Hg) 66, HCO3- (mEq/L) 26**