Postoperative pain is usually treated with opioids. Among them, oxycodone is popular in the
daily practice as it is administered orally and is easily titrated. However, side-effects
include increase duration and frequency of apneic episodes. Some authors believe that
tramadol has less impact on these apneic episodes during the first postoperative night, based
on a trial that reported conclusive results only during the first 2 postoperative hours. The
objective of this randomized controlled trial is to compare the effect of postoperative pain
treatment of oxycodone with tramadol on apneic episodes during the first and third
postoperative nights.