Asthma and COPD Q 46

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A nurse is caring for a client with a nasogastric tube that is attached to low suction. The nurse monitors the client, knowing that the client is at risk for which acid-base disorder?

  

     A. Respiratory acidosis

     B. Respiratory alkalosis

     C. Metabolic acidosis

     D. Metabolic alkalosis

    

    

Correct Answer: D. Metabolic alkalosis

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Loss of gastric fluid via nasogastric suction or vomiting causes metabolic alkalosis as a result of the loss of hydrochloric acid. Stomach fluids are highly acidic at a pH of approximately 1.5 to 3.5. Hydrogen secretion is accomplished via parietal cells in the gastric mucosa. Therefore, the large volume loss of gastric secretions will correlate as a loss of hydrogen chloride, an acidic substance, leading to a relative increase in bicarbonate in the blood, thus driving alkalosis. Losses can occur pathologically via vomitus or nasogastric suctioning.

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Option A: 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 B: 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 C: 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. 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.

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