пн, 09/12/2011

The gentle sleep in the OR

Anesthesia with the noble gas xenon protects heart, circulatory system and brain, but it is expensive. Now it's about which patients need it.

Yet another surgery. The artificial hip joint of the 87-year-old has to be replaced. She's scared. Not so much of the pain but of the aftereffects of the anesthetic. Twice she was confused for days after surgery. The doctors call her condition delirium. A patient experiencing delirium must be monitored in the ICU to take care that they do not fall out of bed and it break their bones.

Chief physician Mathias Reyle-Hahn of Waldkrankenhaus Hospital in Berlin often hears such stories. To prevent those experiences his house, unlike many university hospitals, offers a particularly gentle anesthesia with the noble gas xenon. Many high-risk patients only travel to the outskirts of Berlin because of that: patients with severe heart diseases, multi-allergy sufferers, patients with a known familial predisposition to an overheating of the body called malignant hyperthermia. Here, the muscles react too strongly to conventional anesthetics, for 90 percent of the patients this is fatal. Typical patients are also elderly people who in the past had struggled with severe dementia after anesthesia.

Some patients do not find out of the anesthesia-induced confusion. The older the patient gets, the more likely this scenario becomes. Why, nobody knows. Some only problems have to find the right words or to remember things. Others go over table and benches and want to remove needles. If such a thing occurs, it most likely will happen again at the next operation.

Not with xenon. "In ten years we have not seen a single case of severe delirium after a xenon anesthesia," says Reyle-Hahn. But despite his experience it can not ruled out entirely. "Maybe you overlook mild forms," he says. This must now be studied at university clinics with a larger number of patients.

Nevertheless there is evidence that xenon protects the brain cells - for example, in animal studies with rodents born too early. That this can also work in humans, showed last year Marianne Thoreson, professor of neonatal neuroscience at the University of Bristol, and John Dingley, an anesthesiologist at the Medical College of Swansea University. After an emergency C-section baby Riley Joyce breathed no longer and had no pulse. Even when he survived that, his fate was all but certain. Through the lack of oxygen he was in danger to be left with severe brain damage.

Therefore he was immediately transferred to the experts. An experimental treatment began: they cooled the baby and gave him with a specially designed machine for newborns 200 milliliters of xenon per hour. Seven days later, Riley was already searching for eye contact to his mother and began to drink the first milk. Whether this success can be repeated, is currently being tested in a study.

"These protective properties of xenon are interesting for anesthesia in elderly patients as well," says Claudia Spies, anesthesiologist at Charité hospital in Berlin. Since there is not enough data, clinical research is imperative and meaningful.

But not everyone sees the anesthesia with xenon as positive, particularly because of the high cost of gas is controversial: depending on the length of surgery, the anesthesia will cost 150 to 300 Euro, which ten times more than a conventional anesthesia with other gases as isoflurane and sevoflurane.

For the anesthesiologist Hugo van Aken from University Hospital Münster xenon is a dream: "Of course, one can have an excellent anesthetic with it," he says.

Reyle-Hahn vehemently speaks for xenon: "It's the best anesthetic, which we can offer at this moment," he says. The noble gas is breathed out exactly as it is inhaled. It prevents the heart, the circulatory system and the brain from damage. Even after a 12 to 16-hour operation patients wake up within minutes and can be addressed. Since less complications occur during surgery, the length of stay shortens.

In addition, the cost of anesthesia are negligible in comparison to a day in the ICU.

What is Xenon?

Xenon comes in traces in the atmosphere. It is the most expensive among the noble gases. U.S. combat divers discovered its narcotic effect as they tested noble gases as an oxygen additive. In Germany xenon was approved as an anesthetic in 2005. It is used in enclosed equipment, which recovers the gas from the breathing air of the patient.

Its advantages: The blood pressure remains stable and the heart pumping function is not impaired. In blood the gas hardly dissolves. Therefore it can get out of the body quite quickly. The result: the patient wakes up quickly after surgery.