1. Department of Surgery and Physiology-Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, Porto, Portugal
2. Anaesthesia Department, Centro Hospitalar Universitário de São João, Alameda Professor Hernâni Monteiro, Porto, Portugal
3. Department of Community Medicine, Information and Health Decision Sciences-Faculty of Medicine, University of Porto, Alameda Professor Hernâni Monteiro, Porto, Portugal