Metabolic changes associated with excessive vomiting includes the following -

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.