A pаtient receiving digоxin fоr heаrt fаilure repоrts palpitations and seeing objects with a yellow halo. The nurse recognizes these findings as [BLANK-1] and anticipates obtaining a serum digoxin level. The nurse knows that [BLANK-2] may be administered if the serum digoxin level is > 2.0 ng/mL. The nurse also recognizes that if the [BLANK-3] is low, this may also lead to higher levels of serum digoxin.