Two reasons:
- in hypokalemia acids enter cells in exchange for K+ (to compensate for hypokalemia), this will produce metabolic alkalosis. As we know the in alkaline pH the ammonia stays in NH3 form which is lipophilic and easily cross BBB and hence precipitation of encephalopathy
- When hypokalemia becomes severe, instead of K+ in collecting duct, it’s the H+ which is dumped into the urine and this will create paradoxical aciduria where acids are lost and create alkalosis. And again alkalosis will keep ammonia in NH3 form.
Home point is that anything lead to alkalosis will precipitate encephalopathy. Eg, Diuretics (loop and thiazides) and dehydration (RAAS activation)