Asthma and COPD Q 54

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A nurse understands that the excessive use of oral antacids containing bicarbonate can result in which acid-base disturbance?

  

     A. Respiratory alkalosis

     B. Respiratory acidosis

     C. Metabolic acidosis

     D. Metabolic alkalosis

    

    

Correct Answer: D. Metabolic alkalosis

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Increases in base components occur as a result of oral or parenteral intake of bicarbonates, carbonates, acetates, citrates, or lactates. Excessive use of oral antacids containing bicarbonate can cause metabolic alkalosis. Since antacids are neutralizing agents, they add alkaline substances to the body while reducing acid levels thus increasing pH. Milk-alkali syndrome is a pathology where the patient consumes excessive quantities of oral calcium antacids, which leads to hypercalcemia and varying degrees of renal failure.

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Option A: HCO3 functions as an alkalotic substance. CO2 (carbon dioxide) functions as an acidic substance. Therefore, Increases in HCO3 (bicarbonate) or decreases in CO2 will make blood more alkalotic. The opposite is also true where decreases in HCO3 or an increase in CO2 will make blood more acidic. CO2 levels are physiologically regulated by the pulmonary system through respiration, whereas the HCO3 levels are regulated through the renal system with reabsorption rates.

Option B: In acute respiratory acidosis, there is a sudden elevation of PCO2 because of failure of ventilation. This may be due to cerebrovascular accidents, use of central nervous system (CNS) depressants such as opioids, or inability to use muscles of respiration because of disorders like myasthenia gravis, muscular dystrophy or Guillain-Barre Syndrome. Because of its acute nature, there is a slight compensation occurring minutes after the incidence.

Option C: Intestinal secretions are high in bicarbonate and may be lost through enteric drainage tubes or an ileostomy or with diarrhea. These conditions result in metabolic acidosis. Non-gap metabolic acidosis is primarily due to the loss of bicarbonate, and the main causes of this condition are diarrhea and renal tubular acidosis. Anion gap metabolic acidosis is frequently due to anaerobic metabolism and lactic acid accumulation. While lactate is part of many mnemonics for metabolic acidosis, it is important to distinguish it is not a separate etiology, but rather a consequence of a condition.

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