Author's accepted version (post-print).This manuscript has been accepted for publication in Pain Management Nursing. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all disclaimers that apply to the journal apply to this manuscript. A definitive version was subsequently published in Pain Management Nursing, 16(4) (August 2015). doi: http://dx.doi.org/10.1016/j.pmn.2014.09.006