New system may allow use of xenon to protect newborn brain

Breathing xenon gas can help protect the infant brain from damage caused by oxygen deprivation, but the xenon's high cost and scarcity has precluded its widespread use.

A newly developed "closed circuit system" may make xenon feasible, safe, and cost efficient for use in protecting the brains of critically ill infants, according to a study in the August issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).

The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

Led by Dr. John Dingley of University of Wales, Swansea, a U.K. research team introduces a new method of giving xenon to newborn infants with birth defects and other life-threatening conditions requiring surgery and anesthesia. The usual reason for newborns to undergo surgery is a critical problem with the infants' breathing or circulation that prevents their tissues from getting enough oxygen. This lack of oxygen is particularly damaging to the brain, with long-term consequences for the child.

Although it is chemically considered an inert gas, xenon has profound biological effects - in high concentrations, it can induce unconsciousness. For several years, researchers have known that xenon provides protection against some forms of low-oxygen injury to the brain. However, because xenon is extremely expensive, its use is currently limited to a few experimental centers.

To address this problem, Dr. Dingley and colleagues designed a closed-circuit xenon delivery system. The system takes advantage of the fact that uptake of xenon by the lung is very low - when a given amount of xenon is breathed in, almost all of it is breathed out. The new system, fitted to a conventional newborn ventilator, essentially recaptures the exhaled xenon so that the infant can re-breathe it. The system adds precise amounts of oxygen and other gases as needed.

The researchers tested their closed-circuit xenon delivery system on newborn pigs. They found that they could precisely control the depth of anesthesia, while delivering exactly the right amount of oxygen. The piglets had stable vital signs and recovered without any complications. The xenon system could be used with our without cooling of body temperature (hypothermia) - previously the only technique known to protect the brain in infants with low-oxygen injury.

Using the closed circuit system, the researchers estimate that xenon could be used for surgery in critically ill newborns for as little as $2 per hour. This would allow "responsible use of a restricted global xenon supply in the maximum number of clinical cases per year," according to Dr. Dingley and colleagues. They believe that the simple design and operational cost of the system should make the delivery of xenon - once considered prohibitively expensive for routine medical use - safe and inexpensive for newborns requiring surgery and anesthesia for life-threatening birth defects.


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