Herbs can be helpful, but when used incorrectly, they can also harm. In a survey conducted by the Department of Anesthesiology at the University of Colorado Health Sciences Center, researchers found that out of almost 500 patients, 73 percent had taken alternative medicines before surgery. A significant number of these medicines inhibited blood clotting, affected blood pressure, influenced cardiac function, caused sedation, or changed electrolyte levels. Before undergoing surgery, it's crucial that you report to your surgeon all herbs and supplements you take. And although the American Society of Anesthesiologists has been criticized for being too conservative, consider its recommendations and cautions.

Ephedra, or ma huang (Ephedra sinica). Used as an appetite suppressant in many over-the-counter diet aids. Can react with other medications to cause dangerous elevations in blood pressure or heart rate.

Feverfew (Tanacetum parthenium). Generally taken to quell migraine headaches and arthritis. Could theoretically increase bleeding, especially in patients taking anticlotting medications.

Garlic (Allium sativum). Great for lowering cholesterol, triglyceride levels, and blood pressure, but garlic could also increase bleeding.

Ginger (Zingiber officinale). Can be effective in treating after-surgery nausea, but may increase bleeding.

Ginkgo (Ginkgo biloba). Primarily used to improve memory and heighten mental alertness. Can increase bleeding.

Ginseng (Panax ginseng). A popular herb used for many reasons. The medical community is exploring whether the herb might decrease the effectiveness of anticlotting medications, whether it can increase heart rate or blood pressure, and whether it can cause bleeding in postmenopausal women.

Goldenseal (Hydrastis canadensis). May be used as a laxative or to reduce inflammation. Can also worsen swelling or increase blood pressure.

Kava (Piper methysticum). Typically taken to quell anxiety. May increase the effects of certain antiseizure medications or prolong the effects of certain anesthetics.

Licorice (Glycyrrhiza glabra). Used for treating stomach ulcers. Licorice compounds may cause high blood pressure, swelling, or electrolyte imbalances.

Valerian (Valeriana officinalis). Often used as a sleep aid. Can increase the effects of certain antiseizure medications or prolong the effects of anesthesia.

—P.W.