Study designs of evaluations included in the review
Comparative studies, including clinical trials and observational studies (i.e. cohort and case-control studies), were eligible for inclusion in the review.
Specific interventions included in the review
Studies comparing different types of opioid analgesics in the post-operative period or modes of delivery (e.g. intravenous, spinal or epidural) were eligible for inclusion. Studies comparing intramuscular or subcutaneous delivery methods were excluded from the review. The studies included in the review assessed morphine, fentanyl, hydromorphone, tramadol, meperidine, oxycodone and codeine. Intravenous and epidural modes of drug delivery were compared. In some studies drug administration was patient controlled (patient-controlled analgesia, PCA).
Participants included in the review
The review question and title suggested that studies including elderly patients who had undergone surgery were eligible for inclusion. However, the authors did not report eligibility criteria for patient age or type of surgery and younger patients were included. The studies included in the review assessed various groups of patients with mean ages ranging from 40 to 82.8 years; 2 studies included patients with mean ages of 51 years or less and did not include mainly elderly patients. Various types of surgery were included: hip, knee, abdominal, and breast surgeries, along with unspecified gynaecological and orthopaedic surgeries. One case-control study compared elderly patients experiencing delirium with those not experiencing delirium after gynaecological or orthopaedic surgery.
Outcomes assessed in the review
To be eligible for inclusion, the studies had to assess post-operative cognitive function (POCF) or delirium using defined methods. The studies included in the review assessed POCF using a variety of scales and methods: Digit Symbol Substitution, Trail A, Trail B, Profile of Mood States, Mini Mental Status Examination and Short Portable Mental Status Questionnaire. Delirium was assessed using the Abbreviated Mental Test, Confusion Assessment Method, chart review, or by monitoring clinical signs such as disorientation, hallucination and inappropriate behaviour. Two studies used the American Psychiatric Association's DSM III criteria to define delirium. Some studies also assessed pain using methods such as a visual analogue scale or a verbal rating scale.
How were decisions on the relevance of primary studies made?
One reviewer screened all of the retrieved study abstracts for inclusion or exclusion. A second reviewer validated studies to be included in the review and also checked those excluded studies where uncertainty arose.