This is the Vancouver style for referencing, used at the Univerity of Portsmouth within the School of Pharmacy and Biomedical Sciences and the Radiography departments.
This guide is modelled on Citing Medicine: The NLM Style Guide for Authors, Editors, and Publishers (2nd edition). You may wish to consult this source directly for additional information or examples.
The simple answer is that you don't! Ibid and op cit are used in footnotes and because Vancouver mostly does away with the need for footnotes, students shouldn't now be using these terms. The exception would be the SSHLS History students who are required to use footnotes.