The disclosure relates to a method of treating and/or preventing brain impairment in a subject that has or is susceptible to ammonia neurotoxicity (increased plasma ammonia), by administering a Na-; —K+-2CI- cotransporter isoform 1 (“NKCC1”) inhibitor to the selected subject under conditions effective to treat and/or prevent brain impairment. The disclosure further relates to methods of maintaining the fundamental function of astrocytic potassium buffering and inhibiting accumulation of potassium star rounding astrocytes, both of which involve contacting astrocytes with a NKCC 1 inhibitor.