NHM MP Staff Nurse - 2015
Medical & Surgical Nursing
Hard
What electrolyte abnormality is likely to develop in a patient with vomiting?
Appeared in: NHM MP Staff Nurse - 2015
Explanation
- Vomiting causes the loss of gastric acid (hydrochloric acid), leading to a state of metabolic alkalosis.
- In response to alkalosis, potassium ions (K+) shift from the extracellular fluid into the cells to help correct the pH imbalance, which lowers the serum potassium level.
- The fluid volume lost during vomiting activates the Renin-Angiotensin-Aldosterone System (RAAS).
- Increased aldosterone levels stimulate the kidneys to excrete potassium, further contributing to its depletion.
- The combination of intracellular K+ shift and increased renal K+ loss makes hypokalemia the most probable electrolyte abnormality.
Why Other Options Were Wrong
- Option B: Hyperkalemia (high potassium) is the opposite of what occurs with vomiting. Vomiting leads to potassium loss, not retention.
- Option C: While hyponatremia (low sodium) can occur with vomiting, it is not the most direct or primary consequence. It typically develops secondarily if the patient replaces lost fluids by drinking large amounts of plain water, which dilutes the remaining sodium in the body.
- Option D: Hypernatremia (high sodium) is less common with vomiting. It would only occur in cases of severe dehydration where the loss of water is significantly greater than the loss of sodium, leading to a higher concentration of sodium in the blood.
Related Visual
Clinical Relevance
- Nursing practice connection: Use the key finding related to Pathophysiology of electrolyte imbalances resulting from gastrointestinal fluid loss to guide bedside assessment, documentation, and the next nursing action.
- Nurses must monitor patients with persistent vomiting for signs of hypokalemia, such as muscle weakness, leg cramps, fatigue, and cardiac dysrhythmias.
- ECG monitoring is crucial in severe cases, as hypokalemia can cause characteristic changes like flattened T-waves, prominent U-waves, and increased risk of ventricular arrhythmias.
- Nursing interventions include administering antiemetics to control vomiting, replacing fluids with isotonic solutions (like 0.9% Normal Saline), and administering potassium supplements (oral or IV) as prescribed.
How to Approach the Question
- First, identify the core physiological process in the question: vomiting.
- Recall the composition of the fluid being lost. Gastric fluid is highly acidic (containing HCl) and also contains potassium.
- Analyze the primary consequences of losing this fluid: loss of acid leads to metabolic alkalosis, and loss of volume leads to dehydration and RAAS activation.
- Consider how the body compensates for these changes. Alkalosis causes potassium to shift into cells, and aldosterone (from RAAS) causes the kidneys to waste potassium.
- Synthesize these points: both the cellular shift and renal loss mechanisms drive potassium levels down.
- Evaluate the options based on this understanding. Hypokalemia is the direct and most significant result. The other options are either incorrect (hyperkalemia) or secondary/less likely (hyponatremia, hypernatremia).
Concept Tested & Keywords
- Concept Tested: Pathophysiology of electrolyte imbalances resulting from gastrointestinal fluid loss.
- Stem keywords: electrolyte abnormality, vomiting
- Lead-in keywords: likely to develop
- Clinical cues: Vomiting: This is the key clinical sign, indicating loss of acidic gastric contents, which is central to the resulting electrolyte disturbance.
Question ID
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Reference Book
E6 Medicine Davidson Principles Practice 24e p. 381-383
E6 Nursing Fundamentals Taylor p. 779-781
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