Which of the following is the cause of metabolic acidosis -

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2023

Explanation

Metabolic acidosis is characterized by a primary decrease in serum bicarbonate (HCO3−) concentration, leading to a lower blood pH.
The fluids secreted by the gastrointestinal tract, particularly the small intestine and colon, are rich in bicarbonate.
Severe diarrhea causes the rapid loss of these bicarbonate-rich fluids before they can be reabsorbed.
This loss of a base (bicarbonate) leaves the body with a relative excess of hydrogen ions (acid), resulting in metabolic acidosis.

Option B: Most diuretics, specifically loop and thiazide diuretics, cause metabolic alkalosis, not acidosis.
Option C: Excessive vomiting causes the loss of highly acidic gastric contents (hydrochloric acid).
Option D: Massive transfusion of whole blood can lead to metabolic alkalosis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Causes of Metabolic Acidosis as background academic context rather than a clinical decision trigger.
Nurses must diligently monitor patients with severe diarrhea for signs of dehydration and metabolic acidosis, such as Kussmaul respirations (deep, rapid breathing), confusion, and lethargy.
Accurate monitoring of intake and output, along with daily weights, is a critical nursing intervention to assess fluid status.
Reviewing arterial blood gas (ABG) results is essential to confirm the diagnosis and guide treatment. Key findings for metabolic acidosis are pH below 7.35 and HCO3− below 24 mEq/L.

How to Approach the Question

First, identify the core concept of the question, which is 'metabolic acidosis'.
Recall the definition of metabolic acidosis: a condition of low pH and low bicarbonate (HCO3−) caused by either a loss of base or a gain of acid.
Systematically evaluate each option based on its physiological effect on the body's acid-base balance.
Consider the source of fluid loss for GI-related options. Vomiting is loss from the upper GI tract (stomach acid), leading to alkalosis. Diarrhea is loss from the lower GI tract (intestinal bicarbonate), leading to acidosis.
Eliminate the options that are known causes of metabolic alkalosis (vomiting, diuretics, massive blood transfusion) to arrive at the correct answer.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2B p. 77-79

E6 Medicine Davidson Principles Practice 24e p. 386-388

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