[1] Med Univ Warsaw, Dept Anaesthesiol & Intens Care Educ, 4 Oczki Str, PL-02005 Warsaw, Poland
[2] St Georges Univ Hosp, Dept Anaesthesia, Blackshaw Rd Tooting, London SW17 0QT, England
[3] St Georges Univ Hosp, Chron Pain Serv, Blackshaw Rd Tooting, London SW17 0QT, England
[4] Med Univ Warsaw, Dept Anaesthesiol & Intens Care 1, 4 Lindleya St, PL-02005 Warsaw, Poland