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

bDepartment of Medicine I and Christian Doppler Laboratory on Iron and Phosphate Biology, Medical University of Innsbruck, Innsbruck, Austria

Correspondence to Andrea U. Steinbicker, Department of Anaesthesiology, Intensive Care Medicine and Pain Therapy University Hospital Frankfurt, Johann-Wolfgang-Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany. E-mail: [email protected]