Intrathecal morphine provides effective postoperative pain relief in major orthopaedic surgery. Its use, however, is associated with unpleasant side effects like nausea and vomiting. The effect of different premedications on postoperative emetic sequelae induced by intrathecal morphine was studied in a prospective, double blind study. Sixty patients scheduled for arthroplasty surgery of the lower extremity were anaesthetized with spinal anaesthesia with a combination of isobaric bupivacaine 20 mg and morphine 0.3 mg. For premedication the patients were randomised to three groups of equal size. They received either oral diazepam (5 15 mg), oral promethazine (10 mg) or a combination of promethazine and transdermal scopolamine (1.5 mg).
Sixty percent of the patients with both promethazine and transdermal scopolamine were totally free from postoperative nausea and vomiting (PONV) symptoms compared to those premedicated with diazepam (40%) or promethazine alone (30%). Promethazine together with transdermal scopolamine reduced significantly the number of patients with vomiting (to 25%) and also vomiting episodes. This combination was also more efficient in reducing the incidence of nausea (to 25%) and nausea episodes than promethazine alone (P<0.05). Combination also reduced the requests for additional pain relief (P<0.05). PONV occurred in a majority of patients during the first 12 hours of the 24 hour study period and the need for additional analgesics thereafter. The incidence of itching (50–65%) and urinary catheterisation (55–70%) was similar in all groups.
In conclusion, the combination of oral promethazine and transdermal scopolamine was most effective in reducing PONV symptoms and also reduced the need for postoperative pain treatment.