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Difficulty: EasyPhysiological Adaptation

A young adult arrives at the urgent care clinic complaining of relentless vomiting for the past 24 hours after consuming undercooked seafood. The provider orders a comprehensive metabolic panel and arterial blood gas analysis. The results demonstrate a pH of 7.49, a PaCO2 of 40 mm Hg, and an HCO3- of 30 mEq/L. Which clinical condition do these values represent?

  1. Metabolic alkalosisAnswer
  2. B
    Metabolic acidosis
  3. C
    Respiratory alkalosis
  4. D
    Respiratory acidosis

Answer

Metabolic alkalosis
The client's laboratory results show an elevated pH (7.49), indicating alkalosis, combined with an elevated HCO3- (30 mEq/L), indicating a metabolic origin. The normal PaCO2 (40 mm Hg) rules out a primary respiratory disturbance. Furthermore, the clinical history of severe vomiting supports this finding, as the expulsion of gastric acid naturally leads to metabolic alkalosis.

Step-by-Step Solution

1
Evaluate the client's pH value to determine the primary state of the blood.
The pH is 7.49, which is greater than the normal range of 7.35 to 7.45. This indicates a state of alkalosis.
Identifying whether the blood is acidic or alkaline is the first necessary step in interpreting an arterial blood gas result.
2
Analyze the PaCO2 value to assess the respiratory component.
The PaCO2 is 40 mm Hg, which is perfectly centered within the normal range of 35 to 45 mm Hg.
A normal PaCO2 indicates that the respiratory system is neither the cause of the alkalosis nor has it begun to compensate for it yet.
3
Analyze the HCO3- value to assess the metabolic component.
The HCO3- is 30 mEq/L, which is elevated above the normal range of 22 to 26 mEq/L.
An elevated bicarbonate level corresponds with the alkaline pH, confirming that the origin of the imbalance is metabolic.
4
Correlate the laboratory values with the clinical scenario.
The diagnosis of metabolic alkalosis aligns perfectly with the history of relentless vomiting.
Vomiting causes a profound loss of hydrochloric acid from the stomach, which leaves an excess of bicarbonate in the bloodstream.

Key Concept

Interpretation of Arterial Blood Gases (ABGs) and the physiological effects of upper gastrointestinal fluid loss.
Estimated Time:1m 0s
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Topics

Physiological Adaptation

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