aDepartment of Anaesthesiology, Intensive Care Medicine and Pain Therapy, University Hospital Frankfurt, Goethe University, Frankfurt, Germany

bDepartment of Anaesthesiology, Intensive Care Medicine and Pain Therapy, University Hospital Münster, Germany

Correspondence to Kai Zacharowski, Department of Anaesthesiology, Intensive Care Medicine and Pain Therapy, University Hospital Frankfurt, Goethe University, Frankfurt, Germany. E-mail: [email protected]