CRD summary

This review assessed the effects of opioid analgesics on postoperative delirium and cognitive decline in elderly patients. The authors reported an increased risk of postoperative delirium associated with meperidine, but no apparent differences associated with the mode of drug delivery. Given that studies used different outcome measures and definitions, and lacked statistical power, the authors' findings should be interpreted with caution.

Authors' objectives

To determine the effects of opioid analgesics on post-operative delirium and cognitive decline in elderly patients.

Searching

CINAHL and PubMed were searched from 1966 to 2005; the search terms were reported. In addition, the reference lists of retrieved articles were screened for further studies.

Study selection

Assessment of study quality

The validity of randomised controlled trials (RCTs) was assessed according to randomisation, blinding, and withdrawals and drop-outs. The studies were each awarded a score of between 1 and 5; details of the scoring system were reported. The authors did not state how many reviewers were involved in this process.

Data extraction

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction.

Details of any criteria or definitions used to define delirium or postoperative cognitive function were extracted. Where possible, the power of the studies was extracted or calculated by comparing the proportion of the group of patients with the higher rate of delirium against a hypothesised decrease of 10%, given the sample sizes reported by the study. Outcome data were extracted as reported in the original studies, with percentages or odds ratios (with 95% confidence intervals, CIs) reported, where available, for incidences of delirium.

Methods of synthesis

Results of the review

Ten studies (1,269 participants) were included in the review: seven RCTs (391 participants), one prospective cohort study (541 participants), one retrospective cohort study (92 participants) and one case-control study (245 participants).

Studies comparing different opioid analgesics (three RCTs, one prospective cohort, one retrospective cohort and one case-control study): Most of the studies were limited by small sample sizes. All three RCTs found no significant differences in cognitive function or delirium when comparing patient-controlled analgesia morphine with patient-controlled analgesia fentanyl (quality score 2), patient-controlled analgesia hydromorphone (quality score 4) and patient-controlled analgesia tramadol (quality score 5). The studies comparing morphine with hydromorphone and tramadol did not include mainly elderly participants. All three observational studies found significantly poorer delirium and/or cognitive outcomes for the meperidine groups when comparing meperidine with morphine (retrospective cohort study), morphine and other opiates (prospective cohort), and morphine, fentanyl, oxycodone, and codeine (case-control study).

Studies comparing different modes of delivery (four RCTs and one case-control study): Many studies were limited by small sample sizes and different definitions of postoperative cognitive function and delirium. All five studies assessed predominantly elderly patients. All four RCTs found no significant differences between intravenous and epidural drug delivery with respect to delirium (two trials, both with quality scores of 3) and postoperative cognitive function (two trials, quality scores of 4 and 2). The case-control study found poorer delirium outcomes for patients receiving epidural analgesia. However, 85% of patients in the epidural group received meperidine and no multivariate analysis was performed to take this confounding variable into account.

Authors' conclusions

Evidence suggested an increased risk of post-operative delirium associated with the use of meperidine in elderly surgical patients. There was no evidence of a significant decline in postoperative cognitive function or an increased incidence of delirium in patients receiving other opioids such as morphine, fentanyl or hydromorphone. The mode of drug delivery (intravenous or epidural) did not appear to influence cognitive function. However, further research is required to confirm these findings.

CRD commentary

This review was based on clear inclusion criteria that were defined for the intervention, study design and outcomes, butthe types of participants eligible for inclusion were not defined. Although the title of the review and the research question implied that the review was looking at the effects of opioids in elderly postoperative patients, two of the included studies did not assess mainly elderly participants. The limited literature searches may be subject to publication bias, as no specific attempts were made to locate unpublished data. It was unclear whether language restrictions were imposed. It was difficult to assess whether appropriate steps were taken to reduce the risk of bias and error when assessing the validity of the studies and extracting the study data.

The validity of the RCTs was assessed using limited, but appropriate criteria, but no criteria were reported for an assessment of the other study designs. Details of the individual studies were provided. Given the differences between the studies, a narrative summary of the findings seemed appropriate. However, many of the studies lacked statistical power and comparisons were difficult given the use of different outcome measures and definitions.

Therefore, the review's conclusions should be interpreted with caution.

Implications of the review for practice and research

Practice: The authors stated that meperidine appeared to be the only opioid analgesic whose use should be clearly avoided in elderly patients.

Research: The authors stated that further research was required to confirm the review's findings. Future studies should use standardised measures and definitions of cognitive function and delirium, and use neuropsychological tests to target sensitive domains. Studies should ensure that they recruit sufficient numbers of participants to discern meaningful differences in outcomes, and also assess post-operative pain.

Bibliographic details

Fong H K, Sands L P, Leung J M. The role of postoperative analgesia in delirium and cognitive decline in elderly patients: a systematic review. Anesthesia and Analgesia 2006; 102(4): 1255-1266. [PubMed: 16551934]

Original Paper URL

http://www.anesthesia-analgesia.org/

Indexing Status

Subject indexing assigned by NLM

MeSH

Aged; Analgesics, Opioid /adverse effects; Cognition Disorders /chemically induced /epidemiology; Confusion /chemically induced /epidemiology; Delirium /chemically induced /epidemiology; Humans; Pain, Postoperative /drug therapy /epidemiology /psychology; Randomized Controlled Trials as Topic /statistics & numerical data; Risk Factors

AccessionNumber

12006001684

Database entry date

30/06/2007

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.