This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Metabolic changes associated with excessive vomiting includes the following - 
Select and explain. 
A. Metabolic acidosis, B. Hyperchloremia, C. Hypokalemia, D. Decreases bicarbonates
C: Hypokalemia
Answer: C: Hypokalemia 
Explanation: Vomiting causes loss of gastric secretions which include HCl & K+ ions, resulting in metabolic alkalosis, hypokalemia and hypochloremia.
However note that the moderate to severe hypokalemia seen with excessive vomiting is not merely explained by loss of K+ ions in vomiting.
"In fact the hypokalemia is primarily due to increased renal K+ excretion. Loss of gastric contents results in volume depletion and metabolic alkalosis, both of which promote Kaliuresis." - Harrison 16/e, p 259.