Background: There is evidence in the literature that research sponsored by the pharmaceutical industry is more likely to have favourable outcomes.

Objectives: To determine whether there is an overestimation of the true intervention effect in clinical trials sponsored by pharmaceutical companies compared to non-industry-sponsored studies in anaesthesia clinical outcomes.

Methods: We searched Medline, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), and LILACS for randomised-controlled trials comparing inhalation versus intravenous anaesthetics for adults undergoing on-pump or off-pump coronary artery bypass grafting that reported mortality within 180 days of surgery and/or use of inotropes. Studies should have also reported the funding source.

Results: Twelve studies (n=1782 participants) were included. Pooled estimates of 7 RCTs suggested a significantly increased risk of mortality on studies sponsored by pharmaceutical companies [Relative risk (RR) 0.45, 95% confidence interval (CI) 0.23 to 0.89; I2 = 2%; p = 0.02] versus non-industry-sponsored studies (RR 0.21, 95% CI 0.01 to 4.24; I2 = not applicable; p = 0.31). Estimates of the use of inotropes suggested similar results (RR 0.71, 95% CI 0.48, 1.06; I2 = 27%; p = 0.09 versus; RR 0.77, 95% CI 0.47 to 1.26; I2 = 74%; p = 0.30, respectively), although there is a larger absolute risk reduction (ARR) in the studies sponsored by pharmaceutical companies (29%) compared to those non-industry-sponsored (23%).

Conclusions: There is a similarity between drug companies and Uncle Scrooge related to some economic interests that can cause biased actions. Like Uncle Scrooge, who sometimes takes questionable paths to get to his money, pharmaceutical companies may be using overestimation of the magnitude of treatment effects on their clinical trials. Current evidence is not definitive nor generally realistic, and more careful research is warranted to verify this tendency in other medical areas.