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Hold the eggplant?

And the potatoes? And the tomatoes? The foods you eat a day or two before surgery may change the way your body reacts to anesthesia. Physicians have long wondered why some patients who have many factors in common can have such different responses to the same anesthetic or muscle relaxant. Now, Jonathan Moss and his U of C medical colleagues have demonstrated in a recent study a connection between certain foods and the metabolism of anesthetics.

The results, says Moss, professor of anesthesia and critical care and the study’s director, “bring us one step closer to understanding why patients vary so widely in their sensitivity to certain anesthetic drugs. We now suspect that much of the variability may be due to diet.”

The amount of anesthesia a patient receives is based primarily on his or her age, weight and height, and liver and kidney function, but “those are only part of the picture,” Moss explains. “We need to fill in the rest, including genetic and, now, dietary factors.”

Moss’s study, reported at this fall’s annual meeting of the American Society of Anesthesiologists, suggests that ingesting even small amounts of natural compounds called SGAs (solanaceous glycoalkaloids), produced in eggplants, potatoes, and tomatoes, can slow the metabolism of common anesthetic drugs. SGAs act as insecticides, protecting plants from animals, insects, and fungi.

Potatoes, for example, ordinarily produce high levels of SGAs only in their leaves, stems, and sprouts. When damaged or exposed to light, however, the edible tuber also produces SGAs—as well as chlorophyll, giving it a greenish tint that’s a warning sign of high SGA content.

The U of C researchers found that for several days after ingestion, even in tiny amounts, SGAs slow the breakdown of many commonly used anesthetics and muscle relaxants by inhibiting two important enzymes—butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE). When these enzymes are put out of action, the body can’t break down and eliminate the drugs, so they continue to act long after they should have worn off.

Moss—working with Daniel McGehee, assistant professor of anesthesia and critical care, and M.D./Ph.D. student Matthew Krasowski, AB’93—found that levels of SGAs typically present in the blood of someone who ate moderate amounts of ordinary potatoes days ago can significantly block BuChE and AChE in a test tube. “This may help explain,” Moss says, “why the dosing models of many anesthetic agents are often off by as much as 50 to 100 percent.”

Because the complex process is also affected by genetic factors, there’s no one-size-fits-all outcome, such as surgeons simply telling their patients to skip eggplants, potatoes, and tomatoes before surgery. And though laboratory tests can predict which patients will metabolize drugs slowly, it would not be practical to test patients for SGA levels immediately before surgery, says Moss. Instead, he says, those who design anesthetics should look for methods that don’t rely on BuChE and AChE to regulate drug metabolism.—M.R.Y.

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