CIMIT Summer Series 2009: Frontiers of Inhalation Technologies in Biomedical Sciences and Clinical Medicine
Week Three: ROLE OF INHALATION TECHNOLOGIES FOR ORGAN PROTECTION AND PATIENT SEDATION IN CRITICAL CARE
Moderator: Augustine Choi, MD, Chief, Pulmonary and Critical Care Medicine, Brigham and Women's Hospital; CIMIT Co-Program Leader, Inhalation Technology
Xenon Anesthesia - What Else?
Philippe Richebé, MD, PhD, Associate Professor in Anesthesiology and Pain Medicine, University of Washington Medical Center, Department of Anesthesiology and Pain Medicine
An inert gas, Xenon was first used for its anesthetic properties in the early 50’s. Its anesthetic effects seem to be based on an action on the NMDA glutamate receptors and not by an inhibition of GABA-receptors as most of the anesthetics usable in the clinical daily practice. It showed surprising characteristics regarding onset and recovery of anesthesia. It is not toxic and environmentally friendly.
Xenon got its market authorization in 10 European countries during the last five years. Many clinical studies have evaluated Xenon anesthesia in regards to different criteria. The most interesting results were gathered in clinical studies on hemodynamic stability under Xenon anesthesia. Hemodynamic data (heart rate and blood pressure) were more stable under Xenon anesthesia as compared to other drugs like propofol or halogenous gases, even in patients with preoperative heart failure. Therefore Xenon seems to be a promising anesthetic for patients with compromised cardiac function. As Xenon did show impressive effects in keeping hemodynamic data very stable, it was suggested that it could have also an impact on postoperative cognitive function not only because it would maintain a good level of brain perfusion during anesthesia, but also because of some neuroprotective properties of the gas. Regarding postoperative neurological dysfunction especially in elderly, only one clinical study showed a quicker emergence from anesthesia in elderly but without any change in terms of postoperative cognitive dysfunction in this population. If Xenon has these strong NMDA receptor blocker properties, it would suggest its use would lead also to some decrease of pain sensitization after the surgery as shown with other anti-NMDA drugs, but this point has never been studied yet.
Regarding the technical aspect of the use of Xenon, Xenon has to be used with a specific ventilator in totally closed circuit with micro-injections of gas as needed according to the monitoring of the inspired concentration of Xenon. This new technology in the field of anesthesiology has been developed lately, allowing anesthesiologists to use Xenon at 1 MAC (Minimum Alveolar Concentration) which is 60% (and 40% O2), without having a very high consumption of this gas.
Nevertheless, despite the use of this closed-circuit, Xenon anesthesia remains much more costly as compared to the classical anesthesia with iv propofol or halogenous gases. Moreover, Xenon production has and will have some limitations. Those are the reasons why we should have a better understanding of the real clinical benefits of such an anesthesia with Xenon in order to use it for the right and selected patients.
Clinical Challenges of Xenon Anesthesia: Pros and Cons
Thomas Marx, MD, PD, Anesthesia Pole Leader, Air Liquide
Dr. Thomas Marx, Air Liquide, will explore the history of Xenon, from its first detecton by Ramsey and Travers in 1898 to its use in medicine in deep sea anesthesia when, in 1937, Behnke investigated causes of diver’s delirium, and years following. He will discuss experimental results of xenon anesthesia, its main medical indication in high risk patients and surgery and its use as an agent for high risk patients and surgery, trauma care, long haul transport like MEDEVAC missions and special ICU indications.
After two multicenter trials, xenon was approved for anesthesia in Germany in 2005. The approval of the BfArM; the German Medical authority included cardiovascular risk patients and patients classified to be ASA III. The European Medical Authority in 2007 regarded the number of ASA III patients in those studies to be too low and excluded those patients in 2007. Since then xenon was approved in Europe, but the patients with the highest benefit from xenon administration are excluded.
Air Liquide’s research is concentrated to increase the number of risk patients to re-extend the xenon authorization into this group and, based on the assumption that the mechanisms described are present in the whole organ system, Air Liquide investigates organ protective properties of xenon.
According to Marx, though, problems need to be resolved. For instance, in applying xenon in emergency care, ICU and transports, small and lightweight ventilator devices in “closed system” design are required. Secondly, availability of xenon needs to be increased and missing xenon” needs to be recovered
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I like the presentations but I am afraid being a little bias-challenged.
Posted by: Thomas Marx | 25 August 2009 at 09:57 AM