AIIMS M.Sc. Nsg Entra…: Which acid-base disorder is expected in a patient with prolonged vomiting.?

AIIMS M.Sc. Nsg Entrance exam-2026

Medical & Surgical Nursing

Medium

Appeared in: AIIMS M.Sc. Nsg Entrance exam-2026

Explanation

Prolonged vomiting causes the loss of large amounts of stomach acid (hydrochloric acid, HCl).
The loss of hydrogen ions (H+) from the stomach acid leads to a relative increase in bicarbonate (HCO₃⁻), a base, in the blood.
This primary excess of bicarbonate raises the blood pH above the normal range (greater than 7.45), defining the condition as metabolic alkalosis.
The body attempts to compensate by slowing down breathing (hypoventilation) to retain carbon dioxide (CO₂), which is an acid, but this compensation is often limited.

Option A: Metabolic acidosis is characterized by a primary deficit of bicarbonate (HCO₃⁻) or an excess of acid, which is the opposite of what occurs in vomiting.
Option C: Respiratory acidosis is caused by the retention of carbon dioxide (CO₂) due to inadequate ventilation (hypoventilation), a primary respiratory problem.
Option D: Respiratory alkalosis is caused by excessive loss of carbon dioxide (CO₂) due to rapid breathing (hyperventilation).

Visual 1: Flowchart: Pathophysiology of Metabolic Alkalosis - A visual showing the sequence: Prolonged Vomiting -> Loss of HCl (H+ and Cl-) -> Increased renal reabsorption of HCO₃⁻ -> Increased serum HCO₃⁻ -> Increased pH -> Metabolic Alkalosis.
Visual 2: Diagram: ROME Mnemonic - A simple chart explaining the ROME (Respiratory Opposite, Metabolic Equal) mnemonic for interpreting ABG results, showing how pH and PaCO₂/HCO₃⁻ move in each disorder.

Clinical Relevance

Nursing practice connection: Use the key finding related to Acid-base imbalance caused by prolonged vomiting to guide bedside assessment, documentation, and the next nursing action.
Nurses must monitor patients with prolonged vomiting for signs of metabolic alkalosis, such as confusion, muscle cramps, tingling, and tetany, which result from decreased ionized calcium.
It is crucial to monitor electrolyte levels, especially potassium (K+), as hypokalemia frequently accompanies metabolic alkalosis and can lead to cardiac arrhythmias.
What if? If the patient had severe, prolonged diarrhea instead of vomiting, the expected disorder would be metabolic acidosis due to the loss of bicarbonate-rich intestinal fluid.

How to Approach the Question

First, identify the key physiological process in the question stem: 'prolonged vomiting'.
Recall the contents of stomach fluid. It is highly acidic, containing hydrochloric acid (HCl).
Analyze the effect of losing this fluid. Losing acid (H+ ions) from the body will make the blood more alkaline (basic).
Determine if the primary problem is metabolic or respiratory. Since the issue originates from the loss of stomach contents (a metabolic process), not a breathing problem, it is a metabolic disorder.
Combine the findings: an alkaline state caused by a metabolic process is 'Metabolic Alkalosis'.
Evaluate the options to find the one that matches your conclusion.

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics 22nd Edition (2024) — Volume 1 p. 562-564