Diagnosis is largely based on history and clinical picture; there is no readily available serum test
Serial ECGs
Continuous cardiac monitoring<unk>  itself does not cause electrolyte derangements
Clonidine toxicity
Cholinergic crisis
Tricyclic antidepressant toxicity
Yohimbine toxicity
Antipsychotic toxicity
Flunitrazepam toxicity
Beta-blocker toxicity
Caffeine withdrawal