Which acid-base imbalance is most commonly seen in a patient with severe diarrhea?

Appeared in: NORCET 10 Mains

Explanation

Severe diarrhea causes the loss of large volumes of intestinal fluid.
Intestinal fluid is rich in bicarbonate (HCO3−), which is a base.
The loss of bicarbonate from the body leads to a decrease in the blood's pH, resulting in metabolic acidosis.
This type of acidosis is specifically a normal anion gap metabolic acidosis because chloride is reabsorbed to maintain electrical neutrality as bicarbonate is lost.

Option A: Metabolic alkalosis is caused by the loss of acid, not base.
Option C: Lactic acidosis is a specific type of metabolic acidosis caused by the buildup of lactic acid, not the direct loss of bicarbonate.
Option D: Respiratory acidosis is related to pulmonary function, not the gastrointestinal system.

Clinical Relevance

Nursing practice connection: Use the key finding related to Identification of the acid-base imbalance associated with severe diarrhea to guide bedside assessment, documentation, and the next nursing action.
Nurses must monitor patients with severe diarrhea for signs of dehydration and metabolic acidosis, including assessing vital signs, skin turgor, urine output, and mental status.
Key lab values to monitor are serum electrolytes (especially potassium, which can also be lost), bicarbonate levels, and arterial blood gases (ABGs) to assess the severity of the acidosis.
Nursing interventions include administering IV fluids to correct dehydration and electrolyte imbalances, and potentially bicarbonate if the acidosis is severe, as ordered by the physician.

How to Approach the Question

First, analyze the question's core concept: the effect of 'severe diarrhea' on 'acid-base balance'.
Recall the composition of fluids in the GI tract. The stomach contains acid (HCl), while the lower intestines and pancreas secrete bicarbonate-rich (alkaline) fluids.
Connect the fluid loss to the substance lost. Diarrhea involves the loss of lower intestinal fluid, meaning a loss of bicarbonate (a base).
Determine the resulting imbalance. Losing a base makes the blood more acidic. Therefore, the condition is an acidosis.
Differentiate between metabolic and respiratory causes. Since the origin is the GI system (a metabolic process), not the lungs, it is a metabolic acidosis.
Evaluate the options. Metabolic acidosis directly matches this reasoning. Rule out the other options based on their distinct causes (vomiting for alkalosis, lung issues for respiratory imbalances).

Concept Tested & Keywords

Concept Tested: Identification of the acid-base imbalance associated with severe diarrhea.
Stem keywords: acid-base imbalance, severe diarrhea
Lead-in keywords: most commonly seen
Negative lead-in flag: false

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 559-561

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 82-84

E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 99-101

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