Background and Aims Open abdominal hysterectomy is one of the most performed oncological gynecological surgeries, with an expected moderate to high pain level.

The use of single shot intrathecal morphine (ITM) has an analgesic effect of up to 24h, with patients requiring fewer postoperative IV opioids.

The aim of this study is comparing the analgesic effects and adverse effects of ITM against IV morphine, in cancer patients submitted to open abdominal hysterectomy.

Methods Prospective observational study.

Data collection over a 1-year period.

Inclusion criteria comprised adults submitted to total or radical open abdominal hysterectomy, with total intravenous anaesthesia with intraoperative propofol and fentanyl. Patients with pre-induction ITM administration (100 to 300mcg) and postoperative analgesia with IV morphine patient controlled analgesia and paracetamol, were compared to a control group without spinal opioid.

Descriptive and comparative analysis for analgesic quality and adverse effects in the first 24 hour postoperative period was performed using SPSS software.

Results 36 patients were included in the ITM group and 44 in the control group. Comparative analysis found no significant association between ITM administration and lower static or dynamic pain scores. The ITM group had less PCA rescues (p<0.001) but a higher risk of postoperative vomiting (22% vs 2.2%, p<0.01).

Conclusions ITM administration resulted in significantly less PCA rescue, without perceived analgesic improvement compared with no ITM administration. Patients exhibited more side effects, such as nausea and vomit. Prescribing fixed antiemetics for the first 24 hours might be the best strategy to overcome these side effects.