Preoperative drug therapy >> Effect of beta blockers and statins on outcome

This was an observational study. Differences in outcome between those patients who were and were not taking beta blockers before admission could be because of an effect of beta blockade or because patients with a greater risk of cardiac complications were more likely to be prescribed beta blockers. It had been hoped to apply case-mix corrections to the data but as described in the Methods chapter, this was not possible. Therefore it is unsafe to present any conclusions about outcomes in relation to the use of beta blockade. Similarly, no conclusions on the effect of statins on outcome are presented.