Their goal is to provide a framework for physicians "practicing in the current environment of widespread herbal use" and to encourage patients and physicians to discuss the topic openly and in detail prior to surgery.
"While most of these substances appear to be safe for healthy people, for surgical patients they can affect sedation, pain control, bleeding, heart function, metabolism, immunity and recovery in ways that we are just beginning to understand," said study author Chun-Su Yuan, M.D., Ph.D., assistant professor of anesthesia and associate director of the Tang Center for Herbal Medicine Research at the University of Chicago.
Studies suggest that as many as one-third of pre-surgical patients take herbal medications, but that many of those patients fail to disclose herbal use during pre-operative assessment, even when prompted. Further, physicians often are unsure what to do with the information.
"Physicians need to specifically ask patients about herbal medication use," said co-author Jonathan Moss, M.D., Ph.D, professor of anesthesia and critical care at the University. "Many patients think of herbal medications not as supplements but as drugs. Other patients may not want to admit to their use to physicians. But in order to optimize patient safety and pain control during and after surgery, we need to know what herbal as well as over-the-counter or prescription drugs each patient takes."
Despite their reputation as "mild" or "natural," herbal medications can speed up or slow down the heart rate, inhibit blood clotting, alter the immune system and change the effects and duration of anesthesia.
The American Society of Anesthesiologists has recognized the potential for adverse reactions and suggests that patients stop taking all herbal medications two weeks before surgery. This advice may be difficult to implement, however, since most preoperative evaluations occur only a few days prior to surgery.
So the Chicago researchers began to search for more targeted recommendations. Although there are more than 1,500 herbal medications sold in the United States, they focussed on the eight most common herbs -- echinacea, ephedra, garlic, ginko, ginseng, kava, St. John's wort, and valerian -- which account for 50 percent of all single-herb preparations sold.
The authors found, first of all, a shortage of clinically relevant information. There were no randomized, controlled trials that evaluated the effects of prior herbal medicine use on the period immediately before, during and after surgery.
However, by reviewing the biology of the compounds as well as all studies, case reports, and reviews addressing the safety and pharmacological effects of these eight medications they came up with the following recommendations:
|
Effects of herbal medications and recommendations |
|||
|
Herb |
Relevant effects |
Perioperative concerns |
Recommendations |
|
Boosts immunity |
Allergic reactions, impairs immune suppressive drugs, can cause |
Discontinue as far in advance as possible, especially for transplant patients or those with liver dysfunction. |
|
|
Ephedra (ma huang) |
Increases heart rate, increases blood pressure |
Risk of heart attack, arrhythmias, stroke, interaction with other drugs, kidney stones. |
Discontinue at least 24 hours before surgery. |
|
Garlic (ajo) |
Prevents clotting |
Risk of bleeding, especially when combined with other drugs that inhibit clotting. |
Discontinue at least 7 days before surgery. |
|
Ginko (duck foot, maidenhair, silver apricot) |
Prevents clotting |
Risk of bleeding, especially when combined with other drugs that inhibit clotting. |
Discontinue at least 36 hours before surgery. |
|
Lowers blood glucose, inhibits clotting, |
Lowers blood-sugar levels. Increases risk of bleeding. Interferes with warfarin (an anti-clotting drug). |
Discontinue at least 7 days before surgery. |
|
|
Kava (kawa, awa, intoxicating pepper) |
Sedates, decreases anxiety |
May increase sedative effects of anesthesia. Risks of addiction, tolerance and withdrawal unknown. |
Discontinue at least 24 hours before surgery. |
|
St. John's wort (amber, goatweed, Hypericum, klamatheweed) |
Inhibits re-uptake of neuro-transmitters (similar to Prozac) |
Alters metabolisms of other drugs such as cyclosporin (for transplant patients), warfarin, steroids, protease inhibitors (vs HIV). May interfere with many other drugs. |
Discontinue at least 5 days before surgery. |
|
Sedates |
Could increase effects of sedatives. Long-term use could increase the amount of anesthesia needed. Withdrawal symptoms resemble Valium addiction. |
If possible, taper dose weeks before surgery. If not, continue use until surgery. Treat withdrawal symptoms with benzodiazepines. |
|
The authors caution that even this study has many gaps. Because they are regulated as dietary supplements rather than medications, herbal medications do not undergo the safety and efficacy testing required for new drugs. Further, unlike pharmaceuticals, there is no mechanism to track adverse events caused by herbs.
Herbal medications are even more difficult to study because the ingredients tend to vary enormously from maker to maker and even lot to lot. Potency and purity are inconsistent. Product labels are not always accurate.
In fact, Yuan, who studies the effects of ginseng, has had to work closely with a Wisconsin supplier to obtain consistent supplies of that herb for his research.
Many physicians remain unaware of potential risks associated with herbal medications or how they interact with other drugs, note the authors. Medical schools are just beginning to teach students about herbal preparations and to study their effects systematically.
"If patients use them -- and we know they do -- then we need to know what to expect, how to prevent problems, especially during surgery, and how to respond when something goes wrong." added co-author Michael K. Ang-Lee, M.D., senior anesthesia resident at the University of Chicago.
The authors have appended a list of web sites with reliable information on herbal medicines, including the FDA's Center for Food Safety and Applied Nutrition, The National Center for Complementary and Alternative Medicine, the USDA's Agricultural Research Service, Quackwatch, the National Council Against Health Fraud, HerbMed, and ConsumerLab.
Funding for this study was provided by the Tang Family Foundation and the Clinical Practice Enhancement and Anesthesia Foundation.
Journal
JAMA