The two authors independently abstracted data from the studies on to a standardized data extraction form, which included surgical procedure, sample sizes, IV acetaminophen dose and schedule of administration, active comparator drug if not placebo, primary end point, other end points, rescue analgesic used, whether a power analysis was done, length of follow-up, and funding. Differences between the two reviewers were resolved by reexamination of the original article until consensus was obtained. The Jadad Scale was used to assess the quality of the RCTs.5 It includes five criteria: Is the study randomized? Is the study double blinded? Is there a description of withdrawals (patients that dropped out of study)? Is the randomization adequately described? Is the method for blindness adequately described?
These items elicit “yes” or “no” answers, such that each study was scored from 0 to 5.