NCLEX-RNPhysiological AdaptationMedium
A client with a history of frequent vomiting due to hyperemesis gravidarum has the following labs: pH 7.50, HCO3- 32 mEq/L, PaCO2 44 mmHg, potassium 3.0 mEq/L. Which acid-base disorder does the nurse identify?
- AMetabolic acidosis
- BMetabolic alkalosis
- CRespiratory alkalosis
- DRespiratory acidosis
Show answer & explanationAnswer & explanation
Correct answer: B. Metabolic alkalosis
Loss of gastric hydrochloric acid from prolonged vomiting causes metabolic alkalosis, evidenced by an elevated pH (>7.45) and elevated HCO3- (>26 mEq/L); the near-normal PaCO2 shows minimal respiratory compensation, and hypokalemia commonly accompanies this due to vomiting and the kidney's compensatory potassium wasting.
Why the other options are wrong
- A. Metabolic acidosis would present with a low pH and low HCO3-, opposite of these findings.
- C. Respiratory alkalosis would show a low PaCO2, not elevated HCO3- as the primary abnormality.
- D. Respiratory acidosis would show a low pH with elevated PaCO2.
Metabolic Alkalosis from Vomiting
Loss of gastric acid (HCl) through vomiting or NG suction raises serum bicarbonate and pH, causing metabolic alkalosis.
- Common causes: vomiting, NG suction, diuretics, antacid overuse
- Often accompanied by hypokalemia and hypochloremia
- pH >7.45, HCO3- >26 mEq/L
- Treatment addresses underlying cause and replaces electrolytes
Memory trick: Vomiting Voids acid, raising pH and bicarb