RT Journal Article SR Electronic T1 Higher nurse staffing levels associated with reductions in unplanned readmissions to intensive care or operating theatre, and in postoperative in-hospital mortality in heart surgery patients JF Evidence Based Nursing JO Evid Based Nurs FD BMJ Publishing Group Ltd and RCN Publishing Company Ltd SP 62 OP 63 DO 10.1136/eb-2012-100893 VO 16 IS 2 A1 Frost, Steven A A1 Alexandrou, Evan YR 2013 UL http://ebn.bmj.com/content/16/2/62.abstract AB