Reviewed: Hunt R, Dienemann J, Norton HJ, et al. Aromatherapy as treatment for postoperative nausea: a randomized trial. Anesth Analg. March 5, 2012; [epub ahead of print]. doi:10.1213/ANE.0b013e31824a0b1c.
Patients undergoing surgery with general anesthesia often have the adverse side effect of postoperative nausea. The authors hypothesize that aromatherapy may reduce postoperative nausea. Aromatherapy is appealing because it is (1) noninvasive; (2) any medical staff or patient can use it; and (3) it costs less than antiemetic medication (i.e., medicines that treat nausea and vomiting). However, it is unknown which aromas or combinations of aromas are effective in reducing postoperative nausea. The purpose of this prospective, 4-arm, placebo-controlled clinical trial was to examine the reduction in severity of post-surgery nausea using several essential oils compared with placebo.
Patients (n = 1,151) 18 years of age or older were recruited from 1 ambulatory surgical site in Charlotte, North Carolina. Included patients were not receiving warfarin (Coumadin®), heparin, 325 mg aspirin, or clopidogrel (Plavix®), and did not have a history or diagnosis of bleeding diatheses (a genetic susceptibility to bleeding), or any known allergies to ginger (Zingiber officinale, Zingiberaceae), spearmint (Mentha spicata, Lamiaceae), peppermint (Mentha x piperita), or cardamom (Elettaria cardamomum var. cardamomum, Zingiberaceae). Patients with clotting disorders were excluded.
Patients rated their level of nausea from 0 to 3, with 3 being severe. Those who reported zero or no nausea were not assigned to a treatment group. The control group of this 4-arm clinical study was treated with saline, while the other 3 groups were administered essential oil of ginger; a blend of the essential oils of ginger, spearmint, peppermint, and cardamom (the exact blend was not described); or 70% isopropyl alcohol (which is not normally considered a component of aromatherapy).
One cubic centimeter of the randomly selected aromatherapy was placed on a 2-inch by 2-inch gauze pad. The study could not be blinded because of the specificity of odors. Each patient was instructed to inhale the scent through the nose and exhale through the mouth 3 times. After 5 minutes, each subject was asked to rate the level of nausea again, then the aromatherapy was discontinued. If nausea was rated 1 to 3 at the end of 5 minutes, participants were offered conventional antiemetic medications. The primary endpoint was the change in the postoperative nausea score 5 minutes after aromatherapy administration.
A total of 301 patients reported postoperative nausea and received aromatherapy; 73 patients received normal saline, 78 received 70% isopropyl alcohol, 76 received essential oil of ginger, and 74 received the blend of essential oils of ginger, spearmint, peppermint, and cardamom. There were no significant demographic differences among the groups. Although all 4 groups had shifts toward reduced nausea, ginger alone and the blend produced statistically significant reductions in nausea compared with saline (P = 0.002 and P < 0.001, respectively) and compared with alcohol (P = 0.017 and P < 0.001, respectively). Although nausea was slightly reduced after alcohol aromatherapy, the reduction was not significantly different from saline. There was a trend toward statistical significance indicating that the blend was more effective than ginger alone (P = 0.07). Ginger and the blend also reduced the number of requests for antiemetic medication compared with saline (P = 0.0002 and P ≤ 0.001, respectively).
The authors conclude that aromatherapy with the essential oil of ginger or a blend of the essential oils of ginger, spearmint, peppermint, and cardamom was effective in reducing nausea severity and the need for antiemetic medication after surgery in an acute-care setting. Future research should examine (1) aromatherapy and vomiting prevention, (2) a longer duration of aromatherapy, (3) comparison of these aromatherapeutic agents with additional aromatherapies, (4) a larger study with standardized antiemetic medication treatment before and after surgery with stratified risk factor groups, and (5) efficacy of prophylactic aromatherapy.
One of the problems that occurred during this study was that the oils underwent oxidation, evaporation, and layering (so they were not mixed properly). Accordingly, patients complained that the aromatherapy was not pleasant. The study had to be halted, and the problem remedied. The oil degradation and improper mixing may be a problem in a real-life setting that is not controlled as well as a clinical trial. This may limit the effective use of aromatherapy in a natural postoperative setting. Essential oils are volatile, and proper storage is important. Also, the quality of the essential oil can be a significant factor in efficacy.
—Heather S. Oliff, PhD