Increase in quality, but not quantity, of clinical trials in acute pain: 1992 versus 2007.

The annual number of published clinical trials in acute postoperative pain in adults has changed little in 15 yr and, as a fraction of all clinical trials published in the six highest impact journals in anesthesiology, has actually decreased from 16% (95% confidence interval: 12-20) to 11% (95% confidence interval: 9-15). However, the methodological quality of reports has improved, with explicit statements on power analysis, allocation concealment, and specification of primary end points exceeding 90% of reports in 2007. There has been a shift in hypothesis interests away from neuraxial analgesia and toward multimodal analgesia.