1 Anatomy and Human Embryology Department School of Medicine, University of Barcelona, Barcelona, Spain.
2 Anesthesiology Department Hospital de la Santa Creu I Sant Pau, Barcelona, Spain.
3 Anesthesiology Department Hospital Costa del Sol, Málaga, Spain.
4 Anesthesiology Department Hospital Clinic, Barcelona, Spain, Anatomy and Human Embryology Department School of Medicine, University of Barcelona, Barcelona, Spain, xavi.sala.blanch@gmail.com.