[1] Univ Hosp Cologne, Dept Anaesthesiol & Intens Care Med, Kerpener Str 62, D-50937 Cologne, Germany
[2] Univ Cologne, IMSB, Cologne, Germany
[3] Marienhospital Bruhl GmbH, Dept Anaesthesiol & Intens Care Med, Bruhl, Germany
[4] Childrens Hosp Cologne, Dept Paediat Anaesthesia, Cologne, Germany
[5] Univ Witten Herdecke, Fac Hlth, Witten, Germany