Anesthetics May Aggravate Alzheimer's Disease

A new study has found that certain general anesthetics could increase the risk of elderly patients developing Alzheimer's disease and other memory and attention problems.

Researchers at the University of Pittsburgh Medical School (PA, USA) conducted a series of animal studies and test tube experiments which have revealed that the inhaled anesthetics halothane and isoflurane encourage the binding of beta amyloid proteins. This binding forms clumps or "plaques” that are characteristic of Alzheimer's disease and may contribute to brain cell death. This effect was also shown with the commonly used intravenous anesthetic propofol, at least at higher concentrations. The findings back up a previous study in which the same researchers used nuclear magnetic resonance (NMR) spectroscopy to show that halothane interacts directly with a pocket in the beta amyloid protein, changing its shape and encouraging neighboring proteins to bind. Just six hours of exposure to halothane is sufficient to trigger protein clumping similar to that seen in people with Alzheimer's.

Although halothane is rarely used in North America or Europe, it is commonly used in Asia and Africa because it is very cheap. The other anesthetics studied are more widely used in the United States and Europe, often in combination, although these seem to take longer to exert their potentially deadly effects. The good news is that the intravenous anesthetic thiopental--also known as thiopentone--appears to have no effect on the proteins. The study was presented at the 2007 annual meeting of the Society for Neuroscience held in Atlanta (GA, USA) in October 2006.

"It is a seriously deadly combination when an older person receives halothane,” said lead author Dr. Pravat Mandal, an assistant professor in the department of psychiatry and the center for neuroscience at the University of Pittsburgh, "because as we get older we all have more beta amyloid in our brains.”

The link between surgery and cognitive problems was first noted during the 1950s, but it was never clear whether postoperative cognitive dysfunction (POCD) was the result of the surgery itself or the anesthetics.



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University of Pittsburgh Medical School