Authors' objectives

To assess the effect of analgesic therapies on respiratory function in post-operative patients.

Searching

The search strategy initially involved 12 databases (including nursing, sociological, psychological and pharmacological databases) as part of a broader search for evidence relating to the treatment of acute pain. For the purpose of analyses of pulmonary function, all of the articles that met the inclusion criteria came from MEDLINE. Therefore, only MEDLINE was searched, from 1966 to 1995, using the following search terms and MeSH: 'random', 'pain-postoperative', 'respirat', 'ventilat', 'atelectasis', 'carbon dioxide', 'forced expiratory volume', 'oxygen', 'lung', 'peak expiratory flow rate', 'pulmonary' and 'vital capacity'. The references of retrieved articles were also examined for relevant papers.

Study selection

Assessment of study quality

A cross-section of the available trials was assessed for quality using the methods of Chalmers et al. (see Other Publications of Related Interest no.1) and Liberati et al. (see Other Publications of Related Interest no.2). This involved a standardised checklist that considered internal and external validity.The articles were read and scored by two blinded readers.

Data extraction

All data were extracted by one investigator and verified by a second.

Methods of synthesis

Results of the review

Forty-eight articles were used in the meta-analysis. The total number of participants was not reported. However, the numbers of participants for some of the individual comparisons were reported: incidence of atelectasis for epidural opioids versus systemic opioids (n=769); incidence of pulmonary infection for epidural local anaesthetics versus systemic opioids (n=215); incidence of pulmonary complications for epidural local anaesthetics versus systemic opioids (n=247); and incidence of pulmonary complications for epidural opioids versus systemic opioids (n=148).

The sensitivity analyses indicated that the exclusion of low-quality studies did not change the results, and quality ratings were therefore not taken into account when combining the studies.

A significant decrease in the incidence of atelectasis was found when epidural opioid was compared with systemic opioid (relative risk 0.53, 95% CI: 0.33, 0.85). There was also significant decreases in the incidence of pulmonary infection (relative risk 0.36, 95% CI: 0.21, 0.65) and of pulmonary complications overall (relative risk 0.58, 95% CI: 0.42, 0.80). The greater Pa02 concentration observed when epidural local anaesthetic was compared with systemic opioid (difference -4.57 mmHg, 95% CI: -0.06, -9.07) was also significant.

Differences also occurred that were not statistically significant, but may be clinically important: epidural opioids, compared with systemic opioids, had a weak tendency to reduce the incidence of pulmonary infection; intercostal nerve blockage tended to reduce the incidence of atelectasis and the incidence of pulmonary complications overall.

There were no clinically or statistically significant differences in other measures of pulmonary function (FEV1, FVC, PEFR).

Authors' conclusions

Clinical measures of pulmonary outcome (incidence of atelectasis, infection, and other complications) were significantly improved by epidural opioid and epidural local anaesthetic treatments. Differences in physiological (surrogate) measures of pulmonary function did not reach statistical significance, but this could have been due to either the small number of patients analysed, or the failure of the chosen methods to reflect pulmonary outcome. These reasons could also explain why no significant differences were found for treatments other than epidural opioid and epidural local anaesthetics.

CRD commentary

The authors presented a well-defined review question.

The search strategy was fairly narrow. No unpublished material was included and, therefore, publication bias cannot be ruled out. The authors could have extended their search to include EMBASE, Cancerlit and handsearching.

The inclusion criteria were not clearly stated.

Details of the individual studies were lacking, e.g. there were no details of the age and gender of the participants, or the duration of follow-up. A quality assessment was carried out on a cross-section of the available trials. It was unclear how the authors used quality in their sensitivity analysis if not all the studies were assessed.

The authors stated that the principal weakness of their approach was that they were forced to combine heterogeneous studies in order to pool sufficient data for meaningful analyses. For this reason, the results and conclusions should be treated with caution.

Implications of the review for practice and research

Future research could help to outline possible correlations between pulmonary function and factors such as doses, volumes, and mixtures of drugs used; segmental level of anaesthetic blockade; type of nerve block used; and area of peripheral neural blockade.

Bibliographic details

Ballantyne J C, Carr D B, deFerranti S, Suarez T, Lau J, Chalmers T C, Angelillo I F, Mosteller F. The comparative effects of postoperative analgesic therapies on pulmonary outcome: cumulative meta-analyses of randomized, controlled trials. Anesthesia and Analgesia 1998; 86(3): 598-612. [PubMed: 9495424]

Original Paper URL

http://www.anesthesia-analgesia.org

Other publications of related interest

1. Chalmers TC, Smith H, Blackburn B, Silverman B, Schroeder B, Reitman D, et al. A method for assessing the quality of a randomized control trial. Control Clin Trials 1981;2:31-49. 2. Liberati A, Himel HM, Chalmers TC. A quality assessment of the randomised control trials of primary treatment of breast cancer. J Clin Oncol 1986;4:942-51. 3. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials 1986;7:177-88.

Indexing Status

Subject indexing assigned by NLM

MeSH

Administration, Oral; Anesthesia, Epidural; Anesthetics, Local /administration & dosage; Humans; Lung /physiology; Narcotics /administration & dosage; Pain, Postoperative /drug therapy; Pulmonary Atelectasis /drug therapy; Respiratory Function Tests

AccessionNumber

11998000485

Database entry date

30/09/1999

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.