Laura Girón-Arango1, John Tran2, Philip Wh Peng3. 1. Department of Anesthesia, Hospital Pablo Tobón Uribe, Medellín, Colombia. Electronic address: lgiron@hptu.org.co. 2. Division of Anatomy, Department of Surgery, University of Toronto, Toronto, Canada. 3. Department of Anesthesia and Pain Medicine, Toronto Western Hospital, University of Toronto, Toronto, Canada.