[1] Univ Klinikum Frankfurt, Klin Anasthesiol Intensivmed & Schmerztherapie, Frankfurt, Germany
[2] Clemenshosp Munster, Klin Anasthesiol & Operat Intensivmed, Munster, Germany
[3] Univ Klinikum Wurzburg, Klin & Poliklin Anasthesiol Intensivmed Notfallmed, Wurzburg, Germany
[4] Goethe Univ Frankfurt, Klin Anasthesiol Intensivmed & Schmerztherapie, Univ Klinikum, Theodor Stern Kai 7, D-60590 Frankfurt, Germany