Vomiting generally leads to a hypochloremic, hypokalemic (not always), metabolic alkalosis. According to Smith, “although hypokalemia is a frequent finding, Schwartz and colleagues (2003) reported in a retrospective chart review that 36% of patients with pyloric stenosis were noted to have hyperkalemia”
Importantly, semi-normalization of chloride may be important (and most relevant), as data suggest that 72% of patients with a chloride of 106 mEq/L have achieve resolution of their metabolic alkalosis.
D W Goh, S K Hall, P Gornall, R G Buick, A Green, J J Corkery Plasma chloride and alkalaemia in pyloric stenosis. Br J Surg: 1990, 77(8);922-3