[Organ protection by conditioning]

Recent demographic developments challenge anaesthesiologists with an increasing number of elderly patients with cardiovascular comorbidities undergoing major surgery. Interventions that are capable to increase tissue tolerance against ischemia are of paramount importance. In this context, conditioning is defined as a mechanism that fosters tissue by specific adaptive processes to develop tolerance against a subsequent ischaemia. Dependent upon the temporal relationship between the intervention and the index ischaemia, preconditioning (intervention before ischaemia) is differentiated from postconditioning (intervention upon reperfusion). Ischaemia induced in tissue remote from the target organ is called remote preconditioning. Both brief periods of ischaemia as well as volatile anaesthetics and opioids are able to trigger conditioning. On a cellular level, ATP-dependent potassium channels and the mitochondrial permeability transition pore are thought to be key effectors. Effective conditioning has been unequivocal demonstrated for various tissues in animal experiments. Clinical trials in patients undergoing cardiac surgery have provided evidence for organ protection by conditioning. Large scale multicenter randomised trials, however, are still needed.