Xenon: recent developments and future perspectives.

The noble gas xenon exerts favorable anesthetic properties along with remarkable hemodynamic stability in healthy patients undergoing elective surgery. Recent investigations documented that it does not prolong the duration of widely used neuromuscular blocking agents, including mivacurium and rocuronium. Some studies also suggest reduced neurocognitive compromise in the very early phase after general anesthesia. These properties differ from those observed for conventional inhalational anesthetics like isoflurane, desflurane and sevoflurane. However, a wider use of xenon in daily clinical routine has been limited owing to its higher price and technical restraints regarding economic delivery. Although there are controversial opinions, xenon seems to exert its main anesthetic features via the glutamate receptor. Recently, a novel binding cavity on the NMDA-subtype glutamate receptor has been elucidated that is occupied by xenon as well as isoflurane. Studies utilizing advanced imaging technologies have furthermore revealed that xenon markedly suppresses cerebral blood flow and glucose metabolism in distinct regions of the human brain. These investigations promise to further the understanding of the basic mechanisms underlying the induction and maintenance of anesthesia in general. Results from in vitro studies and various animal models have consistently demonstrated organoprotective properties of xenon, mainly in settings of ischemia and reperfusion injury. Interestingly, these effects have frequently been observed at subanesthetic concentrations and seem to be synergistic when used in combination with therapeutic hypothermia. Future studies will have to prove whether the high costs of xenon administration might be outweighed by its ability to substantially reduce the sequelae of myocardial and cerebral ischemia.