[1] Fdn IRCCS Ca Granda Osped Maggiore Policlin, Dept Anaesthesia & Intens Care, Milan, Italy
[2] Fdn IRCCS Ca Granda Osped Maggiore Policlin, Dept Pediat Surg, Via Commenda 10, I-20122 Milan, Italy
[3] Fdn IRCCS Ca Granda Osped Maggiore Policlin, Dept Epidemiol, Milan, Italy
[4] Univ Milan, Sch Med & Surg, Dept Pediat Surg, Milan, Italy
[5] Hop Univ Necker Enfants Malad, Dept Pediat Anaesthesia, Paris, France
[6] Med Univ Vienna, Dept Pediat Surg, Vienna, Austria