This study is designed to compare a morphine regimen in the form of a standard Post Anaesthetic Care Unit pain protocol with a bolus dose of ketamine to be implemented if the pain protocol has been inadequate. Any patient in pain, despite two doses of morphine will be included. Thereafter the patients will be randomised to receive either a further solution of ketamine or continuation of the morphine protocol. This randomised, double-blinded, trial will be based in the Post Anaesthetic Care Unit under close anaesthetic and nursing staff supervision.