Although herbal medicines are widely used, their use may be associated with physiologic changes that can result in perioperative complications. Ang-Lee and associates reviewed the medical literature to determine effects of the most commonly used herbal medicines (including echinacea, ephedra, garlic, ginkgo, ginseng, kava, St. John's wort, and valerian) on perioperative care. Eliciting information from the patient about the use of herbal medicines is the first step toward preventing and treating complications in the perioperative period. One study found that more than 70 percent of patients did not reveal herbal medication use during preoperative evaluations. Another potential problem is that herbal medicines are not regulated by the U.S. Food and Drug Administration and, consequently, do not have to meet the safety and efficacy requirements of regulated drugs. Adverse events stemming from herbal medication use are rarely reported because there is no standardized procedure for doing so.

Because no randomized controlled trials of the use of these medicines in the perioperative period have been performed, the authors reviewed the literature that contained relevant information about the safety, pharmacokinetics, and pharmacodynamics of herbal medicines. The perioperative effects that occur may be the result of the herbal medicine itself, drug-drug interactions, or changes in absorption, distribution, metabolism, and elimination of other prescription or over-the-counter drugs.

Echinacea is often used to treat upper respiratory infections. Some studies have shown that it may stimulate the immune system. Patients who require the use of immunosuppressants before surgery (e.g., those requiring organ transplantation) should be advised to avoid taking echinacea. Long-term use of echinacea may, however, cause immunosuppression and lead to impaired wound healing and development of opportunistic infections. Some concerns about hepatotoxicity exist as well.

Ephedra (ma huang) is often used to promote weight loss and increase energy. It is also used to treat asthma and bronchitis. Increases in blood pressure and heart rate occur with use of ephedra because it functions as a sympathomimetic agent. Many adverse events, including fatalities, have been reported with the use of this herbal product. Although ephedra contains ephedrine, which is used to treat intraoperative hypotension and bradycardia, preoperative use of ephedra raises concerns. Anesthesia-ephedra interactions, including intraoperative development of ventricular arrhythmias, have been described. Hypersensitivity myocarditis may also occur. Long-term use of ephedra is associated with tachyphylaxis and may cause hemodynamic instability during the perioperative period. Hypertension, coma, and fatal hyperpyrexia may occur when ephedra is used with monoamine oxidase inhibitors.

Atherosclerosis risk is diminished in persons using garlic (specifically, the allicin component). This finding is partially explained by garlic's ability to inhibit platelet aggregation, with one constituent doing so in an irreversible fashion. Garlic also potentiates the effect of other antiplatelet medications. Therefore, concerns about bleeding are of primary concern in patients undergoing surgery. Because of the potentially irreversible effects of garlic, its use should be discontinued at least seven days before surgery. The hypotensive effects of garlic appear to be marginal.

Gingko is promoted as an agent to improve cognitive disorders, vertigo, tinnitus, erectile dysfunction, and altitude sickness. Gingko may have a platelet inhibitory effect that would be of concern in patients undergoing surgery. Its use should be stopped at least 36 hours before surgery.

Ginseng is purported to protect the body against stress. Pharmacologically, ginseng lowers blood glucose levels (even in patients without diabetes mellitus) and, therefore, may cause intraoperative complications, especially in patients who fasted before surgery. Ginseng may also have a platelet inhibitory effect, and this effect may be irreversible. It should be discontinued at least seven days before surgery.

Kava is used as a sedative and an anxiolytic agent. Because it appears to potentiate gamma-aminobutyric acid inhibitory neurotransmitters, it may potentiate anesthesia's sedative effects. It should be discontinued at least 24 hours before surgery.

St. John's wort is used to treat depression (although recent trials have shown no benefit from its use in patients with major depression). It inhibits serotonin, norepinephrine, and dopamine reuptake. A serotonin-excess syndrome may occur with use of St. John's wort. It also increases metabolism of various medications and may interfere with agents used in operative situations. St. John's wort interferes with digoxin metabolism. Because of its long half-life, St. John's wort should be discontinued at least five days before surgery.

Valerian is used as a sedative and will tend to potentiate the effects of various anesthetics or other sedative-hypnotics (such as benzodiazepines). Valerian should not be discontinued abruptly because of associated withdrawal symptoms similar to those experienced by patients taking benzodiazepines. When possible, the doses of valerian should be tapered and discontinued before surgery. If this is not possible, valerian should be continued until surgery, and benzodiazepines should be used to treat withdrawal symptoms, if necessary.

The authors conclude that physicians should be alert to the use of herbal medications by their patients and should specifically ask all preoperative patients about use of these agents. Not all patients will follow their physician's guidelines to discontinue use of herbal medications, so physicians should be able to recognize and treat any complications that occur in the perioperative period. More information on herbal supplements can be found at the Web site of the U.S. Food and Drug Administration's Center for Food Safety and Applied Nutrition (www.fda.gov/Food) and HerbMed (www.herbmed.org).