Purpose: To compare the timing of administration of morphine in patients undergoing painful ambulatory surgical procedures to determine whether there was a difference in postoperative nausea or vomiting (PONV), quality of analgesia, and recovery profile.
Methods: In a double-blinded, placebo-controlled, prospective study, 70 ASA I-II patients were randomized to receive 0.1 mg x kg(-1) morphine intraoperatively (lop) (n=35), or postoperatively (Pop) (n=35). The severity of nausea and pain were measured using visual analog scales (VAS).
Results: There was no difference between the groups in postoperative nausea scores or the incidence of PONV. Upon awakening, patients who received Pop morphine had higher pain VAS scores with movement (7.6 +/- 2 vs 5.4 +/- 3, P < 0.003) and at rest (6.9 +/- 3 vs 5.1 +/- 3, P < 0.013) than the lop morphine group. The total number of PCA attempts and analgesic requirements were similar. Patients who received Pop morphine were able to drink sooner than the lop group (90 +/- 34 vs 111 +/- 38 min, P < 0.05). All other recovery milestones were similar. Times to discharge from hospital were similar.
Conclusions: Administration of 0.1 mg x kg(-1) morphine iv intraoperatively improves postoperative analgesia upon emergence from painful ambulatory surgical procedures without increasing the incidence of PONV There was no increase in PONV when morphine was administered intraoperatively rather than postoperatively.