Prolonged nasogastric suctioning may cause?

Appeared in: AIIMS Rishikesh NO - 2019

Explanation

Prolonged nasogastric (NG) suctioning removes a significant amount of gastric fluid.
Gastric fluid is highly acidic, containing hydrochloric acid (HCl).
The loss of H+ ions from the stomach leads to a relative excess of bicarbonate (HCO₃⁻) in the blood.
This increase in bicarbonate, a base, raises the blood's pH, causing metabolic alkalosis.
The body attempts to compensate by slowing down breathing to retain CO₂ (an acid), but this is often insufficient.

Option A: Respiratory acidosis is caused by hypoventilation (inadequate breathing), which leads to the retention of carbon dioxide (CO₂). It is a respiratory issue, not a metabolic one related to GI losses.
Option B: Metabolic acidosis is the opposite of metabolic alkalosis. It results from a loss of base or a gain of acid. NG suction causes a loss of acid.
Option D: Respiratory alkalosis is caused by hyperventilation (excessive breathing), which leads to blowing off too much CO₂. This is a respiratory issue, not related to GI fluid loss.

Clinical Relevance

Nursing practice connection: Knowing Acid-base imbalance from gastrointestinal fluid loss helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must carefully monitor patients with NG tubes on continuous suction for signs and symptoms of metabolic alkalosis, which include confusion, muscle twitching, bradypnea (slow breathing), and dizziness.
It is crucial to monitor serum electrolyte levels, particularly potassium (K+), as hypokalemia often accompanies metabolic alkalosis.
Accurate intake and output recording is essential to track fluid and electrolyte losses.

How to Approach the Question

First, identify the key procedure in the question: 'prolonged nasogastric suctioning'.
Recall the composition of the fluid being removed. Gastric fluid is highly acidic due to hydrochloric acid (HCl).
Analyze the effect of removing this fluid. Losing a large amount of acid from the body will make the blood more alkaline (basic).
Determine the type of imbalance. Since the cause is a loss of metabolic acids (not a change in breathing/CO₂), it is a 'metabolic' problem.
Combine the findings: The condition is 'metabolic alkalosis'.
Evaluate the other options to confirm your choice. Respiratory issues relate to CO₂, and metabolic acidosis is the opposite condition, caused by base loss or acid gain.

Concept Tested & Keywords

QgXAj4H37G-qXJ_1mebU-7

E6 Physiology Guyton 4SAE Part 2B p. 76-78

Practise the full AIIMS Rishikesh NO - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.