HERBAL MEDICINES

Preoperative use of herbal medicines has been associated with adverse perioperative events.^[2] Surveys estimate that 22% to 32% of patients having surgery use herbal medicines.^{[4] [5] [6]} As pharmacologically active agents, herbal medicines may affect the perioperative period through several mechanisms: direct effects (i.e., intrinsic pharmacologic effects), pharmacodynamic interactions (i.e., alteration of the action of conventional drugs at effector sites), and pharmacokinetic interactions (i.e., alteration of the absorption, distribution, metabolism, and elimination of conventional drugs). Because approximately one half of herbal medicine users take multiple herbs concomitantly,^[5] adverse effects are difficult to predict and attribute. For example, PC-SPES, a commercially available combination of eight herbs used by patients with prostate cancer, has been associated with thrombotic (i.e., deep venous thrombosis and pulmonary embolism) and hemorrhagic (i.e., anticoagulation from phytocoumarins) complications. ^[7]

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Herbal medicines are associated with problems not usually found with conventional drugs.^[8] Because herbal medicines are classified as dietary supplements, they are not subject to preclinical animal studies, premarketing controlled clinical trials, or postmarketing surveillance. Under current law, the burden is shifted to the U.S. Food and Drug Administration (FDA) to prove products unsafe before they can be withdrawn from the market. Commercial herbal medicine preparations may have unpredictable pharmacologic effects resulting from inaccurate labeling, misidentified plants, adulterants, natural potency variations, and unstandardized processing methods.

In this chapter, we discuss the preoperative assessment and management of patients who use herbal medicines and examine nine herbal medicines that have the greatest impact on perioperative patient care: echinacea, ephedra, garlic, ginkgo biloba, ginseng, kava, saw palmetto, St. John's wort, and valerian ( Table 15-2 ). These nine account for 50% of the herbal medicines sold in the United States^[9] ( Table 15-3 ). Print and Internet resources for additional information on herbal medicines are provided in Table 15-4 .

Preoperative Assessment and Management

The preoperative assessment should address the use of herbal medicines (see Chapter 25 ). More than 70% of patients are not forthcoming about their herbal medicine use during routine preoperative assessment.^[5] When a positive history of herbal medicine use is obtained, one of five patients is unable to properly identify the preparation being taken.^[13] Patients should be asked to bring their herbal medicines and other dietary supplements with them at the time of the preoperative evaluation. A positive history of herbal medicine use should also prompt anesthesiologists to suspect the presence of undiagnosed disorders causing symptoms leading to self-medication. Patients who use herbal medicines may be more likely than those who do not to avoid conventional diagnosis and therapy. ^[14]

Herbal medicines should be discontinued preoperatively. When pharmacokinetic data for the active constituents in an herbal medication are available, the timeframe for preoperative discontinuation can be tailored. For other herbal medicines, 2 weeks is recommended.^[15] However, because many patients require nonelective surgery, are not evaluated until the day of surgery, or are noncompliant with instructions to discontinue herbal medications preoperatively in clinical practice, they may take herbal medicines until the day of surgery. In this common situation, anesthesia can usually proceed safely at the discretion of the anesthesiologist, who should be familiar with commonly used herbal medicines to avoid or recognize and treat complications that may arise. For instance, recent use of herbal medicines that inhibit platelet function (e.g., garlic, ginseng, ginkgo biloba) may warrant specific strategies in the face of procedures with substantial intraoperative blood loss (e.g., platelet transfusion) and those that alter the risk-benefit ratio of using certain anesthetic techniques (e.g., neuraxial blockade).

Preoperative discontinuation of all herbal medicines may not eliminate complications related to their use. Withdrawal of regular medications is associated with increased morbidity and mortality after surgery.^[16] In alcoholics, preoperative abstinence may result in poorer postoperative outcome than continued preoperative drinking.^[17] The danger of abstinence after long-term use may be similar with herbal medicines such as valerian, which has the potential to produce acute withdrawal after long-term use.