Persistent vomiting in G.O.O. causes -a) Hyponatremic hyperchloremia occurb) Hypernatremia without |ed Cl- alkalosisc) Hypokalemic metabolic alkalosisd) Paradoxical aciduria

**Core Concept**
Persistent vomiting in a patient with gastrointestinal obstruction (G.O.O.) leads to loss of gastric contents, which are rich in hydrogen ions (H+), chloride (Cl-), and potassium (K+). This results in a complex disturbance of electrolyte and acid-base balance.

**Why the Correct Answer is Right**
The correct answer is C) Hypokalemic metabolic alkalosis. When gastric contents are lost, hydrogen ions, chloride, and potassium are also lost. The body compensates for the loss of hydrogen ions by increasing renal excretion of hydrogen ions, leading to metabolic alkalosis. Additionally, potassium is lost in the vomit, causing hypokalemia. The kidneys attempt to conserve sodium and water by increasing sodium reabsorption in the proximal tubule, which leads to a mild increase in sodium levels. However, potassium loss is more significant, resulting in hypokalemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyponatremic hyperchloremia occurs when there is a loss of sodium and chloride in the urine, typically seen in conditions like SIADH or heart failure, not in gastric obstruction with vomiting.

**Option B:** Hypernatremia without increased Cl- alkalosis is not typically seen in gastric obstruction with vomiting, as the loss of hydrogen ions and chloride ions usually leads to metabolic alkalosis.

**Option D:** Paradoxical aciduria refers to the acidification of the urine in the presence of metabolic alkalosis, which is not a typical consequence of gastric obstruction with vomiting.

**Clinical Pearl / High-Yield Fact**
Remember, the key to differentiating between metabolic acidosis and metabolic alkalosis is to assess the anion gap and the serum chloride levels. Metabolic alkalosis typically presents with a low anion gap and high chloride levels.

**Correct Answer: C. Hypokalemic metabolic alkalosis**