[1] Univ Med Ctr Hamburg Eppendorf, Ctr Anesthesiol & Intens Care Med, Dept Anesthesiol, Hamburg, Germany
[2] Outcomes Res Consortium, Cleveland, OH 44195 USA
[3] Cleveland Clin, Anesthesiol Inst, Dept Outcomes Res, Cleveland, OH USA
[4] Cleveland Clin, Anesthesiol Inst, Dept Gen Anesthesiol, Cleveland, OH USA