1. Effect of combining tramadol and morphine in adult surgical patients: a systematic review and meta-analysis of randomized trials 
V. Martinez, L. Guichard, D. Fletcher 
British Journal of Anaesthesia 
Volume 114, Issue 3, Pages (March 2015)
DOI: /bja/aeu414
Copyright © 2015 The Author(s) Terms and Conditions

2. Fig 1
Flow diagram.
British Journal of Anaesthesia  , DOI: ( /bja/aeu414)
Copyright © 2015 The Author(s) Terms and Conditions

3. Fig 2 Risk of bias summary.
British Journal of Anaesthesia  , DOI: ( /bja/aeu414)
Copyright © 2015 The Author(s) Terms and Conditions

4. Fig 3
Forest plot for morphine consumption at 4, 12, and 24 h after surgery.
British Journal of Anaesthesia  , DOI: ( /bja/aeu414)
Copyright © 2015 The Author(s) Terms and Conditions

5. Fig 4 Forest plot for pain in PACU, at 4, 12, and 24 h after surgery.
British Journal of Anaesthesia  , DOI: ( /bja/aeu414)
Copyright © 2015 The Author(s) Terms and Conditions

6. Fig 5
Funnel plot for morphine consumption and pain at 24 h after surgery.
British Journal of Anaesthesia  , DOI: ( /bja/aeu414)
Copyright © 2015 The Author(s) Terms and Conditions