A nurse is analyzing the arterial blood gas (ABG) results of a patient.


The patient’s ABGs are: pH:7.6, PaCO2:40 mm Hg, HCO3:32 mEq/L. Which of the following acid-base conditions should the nurse identify the patient is experiencing?

Choice A rationale:

Metabolic alkalosis is characterized by a high pH (above 7.45), high bicarbonate (HCO3-) levels, and normal or low PaCO2. The patient's ABGs show a low pH (7.26), low bicarbonate (14 mEq/L), and low PaCO2 (30 mm Hg), which are not consistent with metabolic alkalosis.

Choice C rationale:

Respiratory alkalosis is characterized by a high pH (above 7.45), low PaCO2, and normal or slightly elevated bicarbonate levels. The patient's ABGs do show a low PaCO2, but the pH is low (acidic) and the bicarbonate is low, which are not consistent with respiratory alkalosis.

Choice D rationale:

Respiratory acidosis is characterized by a low pH (below 7.35), high PaCO2, and normal or slightly elevated bicarbonate levels. The patient's ABGs do show a low pH, but the PaCO2 is also low, which is not consistent with respiratory acidosis.

Rationale for the correct answer, B:

Metabolic acidosis is characterized by a low pH (below 7.35), low bicarbonate levels, and normal or low PaCO2. The patient's ABGs are consistent with metabolic acidosis because they show a low pH (7.26), low bicarbonate (14 mEq/L), and low PaCO2 (30 mm Hg).

Acute kidney injury is a common cause of metabolic acidosis. The kidneys play a vital role in regulating acid-base balance by excreting acids and reabsorbing bicarbonate. When the kidneys are damaged, they are unable to excrete acids effectively, leading to an accumulation of acids in the blood and a decrease in bicarbonate levels.

Additional Information:

It's important to note that the patient's low PaCO2 is likely a compensatory mechanism for the metabolic acidosis. In response to acidosis, the respiratory system tries to increase ventilation to blow off more carbon dioxide, which helps to raise the pH. However, this compensatory mechanism is often not enough to fully correct the acidosis.

Choice A rationale:

Naloxone does not have any direct effect on respiratory secretions. It works by binding to opioid receptors in the brain and reversing the effects of opioids, such as respiratory depression.

While opioids can cause a decrease in respiratory secretions, this is not the primary reason for administering naloxone.

It is important to note that naloxone can actually worsen respiratory secretions in some patients, particularly those with chronic obstructive pulmonary disease (COPD) or other respiratory conditions.

Choice B rationale:

Naloxone is a medication that is specifically designed to block the effects of opioids on the central nervous system (CNS).

It is a competitive antagonist, which means that it binds to opioid receptors in the brain and prevents opioids from binding to those receptors.

This can reverse the effects of opioids, such as respiratory depression, sedation, and hypotension.

Naloxone is often used to treat opioid overdose, but it can also be used to prevent opioid-induced respiratory depression in patients who are receiving opioids for pain relief.

Choice C rationale:

Naloxone is not effective in treating nausea.

In fact, it can actually worsen nausea in some patients.

This is because naloxone can block the effects of opioids in the brain, and opioids can sometimes have a nausea-relieving effect.

Choice D rationale:

Naloxone is not effective in treating urinary retention.

Urinary retention is a common side effect of opioids, but it is not caused by the effects of opioids on the CNS. Urinary retention is typically caused by the effects of opioids on the bladder muscles.