Fluid & Electrolyte Q 49

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Respiratory regulation of acids and bases involves:

  

    A. Hydrogen

    B. Hydroxide

    C. Oxygen

    D. Carbon dioxide

    

    

Correct Answer: D. Carbon dioxide

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Respiratory regulation of acid-base balance involves the elimination or retention of carbon dioxide. Arterial blood gas interpretation is best approached systematically. Interpretation leads to an understanding of the degree or severity of abnormalities, whether the abnormalities are acute or chronic, and if the primary disorder is metabolic or respiratory in origin.

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Option A: When assessing the acid-base balance, most ABG analyzers measure the pH and PaCO2 directly. A derivative of the Hasselbach equation calculates the serum bicarbonate (HCO3) and base deficit or excess. This calculation frequently results in a discrepancy from the measured due to the blood CO2 unaccounted for by the equation.

Option B: The measured HCO3 uses a strong alkali that liberates all CO2 in serum, including dissolved CO2, carbamino compounds, and carbonic acid. The calculation only accounts for dissolved CO2; this measurement using a standard chemistry analysis will likely be called a “total CO2”.

Option C: A “blood gas analysis” can be performed on blood obtained from anywhere in the circulatory system (artery, vein, or capillary). An arterial blood gas (ABG) tests explicitly blood taken from an artery.

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