Background and Goal of Study: Opioids provide an excellent analgesic effect peri-operatively, however, like every drug, not without side-effects. Post-operative complications, such as respiratory depression, post-operative nausea and vomiting, pruritus, difficulty voiding and ileus are well known.
In this study, analgesic requirement was examined after patients received opiate anesthesia and non-opiate anesthesia. 
Materials and methods: A randomized controlled trial containing two groups with each 33 breast cancer patients undergoing a mastectomy or lumpectomy associated with a total axillary dissection was conducted between 29/09/2014 and 09/07/2015 at the Jules Bordet Institute, Brussels.
Per-operative non-opiate analgesia was obtained by combining clonidine (0.2 mcg/kg), ketamine (0.3 mg/kg) and lidocaine (1.5 mg/kg). An extra bolus of ketamine (0.2mg/kg) was given if necessary.
Opiate analgesia was obtained via a combination of remifentanil TCI, ketamine (0.3 mg/kg) and lidocaine (1.5 mg/kg). 
Both groups received IV paracetamol (1000mg/6h) and IV diclofenac (75 mg/12h). 
Patients received a PCA (patient-controlled analgesia) pump for breakthrough pain during the first 24 hours post-operatively. 
Clinical characteristics and post-operative piritramide consumption were assessed during the first 24 hours post-operatively.
Non parametric Wilcoxon test was used to compare postoperative piritramide consumption.
Results and discussion: Data were lacking for two patients in the non-opiate group. A total of 64 patients were included in the study.
In the PACU, immediate piritramide usage was 3.0 (2.0-6.0) mg in the opioid free group and 4.6 (4.0-6.0) in the opioid group. (P> 0.05) 
The total piritramide usage 24 hours post-operatively was 8.1 (2.0-14.5) mg in the non-opiate group and 13.1 (6.0-16.0) mg in the opioid group. (P< 0.05) The difference observed was statistically significant. Thus, these values show that patients in the nonopiate group require less analgesics 24 hours postoperatively.
Conclusion(s): Non-opiate anesthesia is safe in breast cancer surgery. Patients require less analgesics 24 hours after a non-opiate anesthesia than after an opiate anesthesia.

Comparing analgesic requirements after a non-opiate anesthesia and an opiate anesthesia in breast cancer patients: a prospective randomized, double-blinded, controlled trial