Nasogastric suction causes which type of acid-base imbalance?

Appeared in: NORCET 1 - 2020

Explanation

Nasogastric (NG) suction removes gastric fluid, which is rich in hydrochloric acid (HCl).
The loss of hydrogen ions (H+), a metabolic acid, from the body leads to a relative increase in bicarbonate (HCO3−) concentration in the blood.
This shift raises the blood pH above the normal range (greater than 7.45), resulting in metabolic alkalosis.
The kidneys attempt to compensate by retaining H+ and excreting more bicarbonate, but this process is often insufficient to correct the imbalance caused by significant gastric losses.

Option A: This condition is caused by a loss of base or a gain of acid, not the loss of gastric acid.
Option C: This is a respiratory problem caused by retaining carbon dioxide (CO2), not a metabolic issue related to gastric fluid.
Option D: This is a respiratory problem caused by blowing off too much CO2, not a metabolic issue.

Clinical Relevance

Nursing practice connection: Knowing Pathophysiology of acid-base imbalances resulting from gastrointestinal fluid loss helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must monitor patients with NG suction for signs of metabolic alkalosis, such as confusion, muscle twitching, and tingling, and check electrolyte levels (especially potassium, which is also lost).
Monitoring intake and output, as well as laboratory values (ABGs, electrolytes), is a critical nursing responsibility to detect and manage this complication early.
What if?: If the patient had severe diarrhea instead of NG suction, the most likely imbalance would be metabolic acidosis due to the loss of bicarbonate-rich intestinal fluid.

How to Approach the Question

First, identify the core process in the question: 'Nasogastric suction.'
Recall the nature of the fluid being removed. Gastric fluid is highly acidic (hydrochloric acid).
Reason about the effect of removing this fluid. Removing acid from the body will make the body more alkaline (basic).
Determine if the cause is metabolic or respiratory. Since the cause is the loss of stomach acid (a metabolic component), the imbalance is metabolic.
Combine these insights: a metabolic process leading to an alkaline state is 'metabolic alkalosis.'
Evaluate the options to confirm your conclusion and rule out the others based on their distinct causes (respiratory issues or loss of base).

Concept Tested & Keywords

Concept Tested: Pathophysiology of acid-base imbalances resulting from gastrointestinal fluid loss.
Stem keywords: Nasogastric suction, acid-base imbalance
Lead-in keywords: which type
Negative lead-in flag: false

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E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 57-59

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

E6 Nursing Fundamentals Taylor p. 780-782

Practise the full NORCET 1 - 2020

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