Arterial blood gas result showing PH 7.45 and PCO2 30 mm of Hg and HCO3, 22 MEq/L can be interpreted as?

SCTIMST Staff Nurse - 2015 (Set-B)

Medical & Surgical Nursing

Hard

Appeared in: SCTIMST Staff Nurse - 2015 (Set-B)

Explanation

The primary acid-base disturbance is respiratory alkalosis, indicated by a low PaCO₂ of 30 mm Hg (normal: 35-45 mm Hg).
This low PaCO₂ is a result of hyperventilation, where the lungs excrete too much CO₂.
The body compensates for this via the kidneys, which excrete bicarbonate (HCO₃⁻) to bring the pH down.
The HCO₃⁻ of 22 mEq/L is on the low side of the normal range (22-26 mEq/L), reflecting this renal compensation.
Since the pH has returned to the normal range (7.35-7.45), the condition is considered fully compensated.

Option A: Although the pH and HCO₃⁻ values are within their normal ranges, the PaCO₂ is significantly low (30 mm Hg). A truly 'Normal' ABG would have all three values within their respective normal ranges.
Option C: This refers to uncompensated respiratory alkalosis. In an uncompensated state, the compensatory mechanism (renal system) has not had time to act, so the HCO₃⁻ would be normal (around 24-26 mEq/L) and the pH would be high (greater than 7.45).
Option D: Respiratory acidosis involves a high PaCO₂ (greater than 45 mm Hg) due to hypoventilation, leading to a low pH (less than 7.35). The given values are the opposite of this condition.

Clinical Relevance

Nursing practice connection: Knowing Interpretation of Arterial Blood Gas (ABG) results to identify acid-base imbalances helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses frequently monitor ABG results to assess a patient's oxygenation and acid-base status, especially in critical care settings.
Recognizing compensated respiratory alkalosis is crucial as it indicates an underlying problem (like anxiety, pain, or hypoxemia) has been present long enough for the kidneys to react.
Nursing interventions for respiratory alkalosis focus on treating the root cause, such as managing pain, reducing anxiety, coaching slow breathing, or correcting hypoxemia.

How to Approach the Question

First, look at the pH. Classify it as acidosis (less than 7.35), normal (7.35-7.45), or alkalosis (greater than 7.45). A value of 7.45 is on the edge of alkalosis.
Next, examine the PaCO₂ (the respiratory parameter). A low value (less than 35) indicates respiratory alkalosis; a high value (greater than 45) indicates respiratory acidosis. Here, 30 is low, pointing to respiratory alkalosis.
Then, look at the HCO₃⁻ (the metabolic parameter). A low value (less than 22) indicates metabolic acidosis; a high value (greater than 26) indicates metabolic alkalosis.
Determine the primary cause by matching the parameter (PaCO₂ or HCO₃⁻) that corresponds with the pH direction. Here, the low PaCO₂ (alkalosis) matches the alkalotic pH.
Finally, assess for compensation. If the other parameter (in this case, HCO₃⁻) is moving in a direction to counteract the primary disorder and the pH is back in the normal range, it is fully compensated. Here, the HCO₃⁻ is low-normal, showing compensation, and the pH is normal, confirming full compensation.

Concept Tested & Keywords

Concept Tested: Interpretation of Arterial Blood Gas (ABG) results to identify acid-base imbalances.
Stem keywords: Arterial blood gas, PH 7.45, PCO2 30 mm of Hg, HCO3 22 MEq/L
Lead-in keywords: interpreted as

QgBb8303zUg1AjgAk5iSkS

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 56-58

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 558-560