Make sure the patient has adequate analgesia. It may be better to prescribe at fixed intervals rather on a demand basis for the first 12-24 hours so that the patient doesn't have to complain of pain before they receive analgesia. If in doubt, ASK. Be wary of opiate overdosing in elderly patients.
Patient controlled analgesia (PCA) systems are prescribed and administered by the Anaesthetic Department but you should be familiar with these systems.