Yes, I think that written policies have to be adopted for using abbreviations considering patients' safety. The Stanford Hospital Medical Board has adopted an abbreviation policy which comprises a list of 'approved acronyms, abbreviations and symbols to guide documentation and interpretation of hand-written notes'. Apart from this, the policy also includes a list of 'dangerous abbreviations and symbols' that should not be used. Some vital features of the policy includes that medication names should not be abbreviated and that use of metric system is strongly recommended.
Use of abbreviations, acronyms and symbols is acceptable when used for a valid reason and under proper circumstances. For instance, abbreviations can be standardized and developed by individual organizations. Abbreviations can be accepted when used for a published reference source. A list of acceptable abbreviations can be put forward and a proposal can be laid to individuals who work in a particular organization to use abbreviations, acronyms or symbols that are present in the list.