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*Department of Anesthesiology, Chi-Mei Medical Center, Tainan, Taiwan;
Department of Anesthesiology, Municipal Womens and Childrens General Hospital, Kaohsiung, Taiwan; and
Department of Anesthesiology, Tri-Service General Hospital, Taipei, Taiwan
Address correspondence and reprint requests to Jhi-Joung Wang, MD, DMS, Department of Anesthesiology, Chi-Mei Medical Center, No. 901, Chung-Hwa Rd., Yung-Kang City, Tainan, Taiwan. Address e-mail to 400003{at}mail.chimei.org.tw
| Abstract |
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IMPLICATIONS: We compared the prophylactic IV administration of tropisetron 5 mg to prevent postoperative nausea and vomiting (PONV) associated with epidural morphine with dexamethasone 5 mg and saline in women undergoing hysterectomy. We found that tropisetron 5 mg did not significantly reduce the occurrence of PONV associated with epidural morphine. Dexamethasone 5 mg was effective for this purpose.
| Introduction |
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In patients receiving epidural morphine for postoperative pain control, the incidence of nausea and vomiting is frequent (30%62%) (7,8). Because tropisetron provides a significant antiemetic effect in various conditions, it may also be effective in the prevention of epidural morphine-related nausea and vomiting. However, this has never been tested. The aim of the study was to evaluate the prophylactic effect on PONV of tropisetron 5 mg, dexamethasone, and saline in women who after abdominal surgery received epidural morphine for postoperative pain relief.
| Methods |
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Before the study, patients provided detailed medical histories and demographic information, including age, weight, height, time of last menstrual cycle, and drug consumption. All operations took place between 8:00 AM and 2:00 PM. Surgical anesthesia to the T6 dermatome level was provided by 0.3 mL/kg lidocaine 2% (with 1:100,000 epinephrine) followed by intermittent injections of 3 mL of lidocaine 2% (with epinephrine) as necessary through an epidural catheter in the L3-4 or L4-5 interspace. During surgery, IV midazolam 2.55 mg was given for sedation; no supplemental analgesic was given.
Before surgery, a randomization table was used to assign patients to one of three groups of 40 patients to receive IV tropisetron 5 mg, dexamethasone 5 mg, or saline at the end of surgery. The medications (5 mL) were given by slow IV push (>30 s). One minute after injection, all patients received 3 mg of preservative-free morphine in 10 mL of isotonic sodium chloride solution through the epidural catheter for postoperative analgesia. The randomized process and the identity of the study drugs were blinded from the patients, the anesthesiologists during surgery, and the investigators who collected the postoperative data.
Postoperatively, patients were observed for 24 h. A team of nurse-anesthetists collected the postoperative data. During the observation period, arterial blood pressure, heart rate, and respiratory rate were monitored every 4 h (from 8:00 AM to 10:00 PM).
PONV was evaluated by using the following variables: the incidences, the number of episodes of vomiting, and rescue antiemetics. Nausea was defined as the subjectively unpleasant sensation associated with awareness of the urge to vomit. It was assessed while patients were lying still. Vomiting was defined as the forceful expulsion of gastric contents from the mouth. For the purpose of data collection, retching (the same as vomiting but without expulsion of gastric contents) was considered vomiting. A vomiting episode was defined as the events of vomiting that occurred in a rapid sequence (<1 min between events). If events of vomiting were separated by more than 1 min, they were considered to be separate episodes (9,10). Rescue antiemetics (IV droperidol 1.25 mg) were given at patient request. The treatment was repeated if necessary.
Postoperative wound pain at rest was assessed with a 10-cm visual analog scale (VAS; 0 = no pain to 10 = most severe pain) score. When patients complained of excessive pain and requested analgesia, IM diclofenac 75 mg (every 12 h) was given (11). The postoperative data (e.g., nausea, vomiting, and pain) were collected every 4 h (between 8:00 AM and 10:00 PM) by direct questioning by a team of nurse-anesthetists.
Pruritus was assessed by using a three-point ordinal scale (0 = none, 1 = pruritus but only in a small area of the body, 2 = generalized pruritus) (10,12). Pruritus was treated with IM diphenhydramine (20 mg every 4 h as needed) (10,12). The occurrence of side effects related to the use of tropisetron, such as headache, was also evaluated. Headache was assessed as mild, moderate, or severe.
Sample size was predetermined by using a power analysis based on the assumptions that (a) the total incidence of PONV in the Saline group would be 56% (9,10), (b) a 40% reduction in the total incidence of PONV (from 56% to 34%) in the treatment groups would be of clinical relevance, and (c)
= 0.05 and ß = 0.2 (13). The analysis showed that 40 patients per group would be sufficient. A series of one-way analyses of variance was conducted to examine differences among the three groups with respect to parametric variables. If a significant difference was found, the Bonferroni t-test was used to detect the intergroup differences. The Kruskal-Wallis test was used to determine differences among the three groups with respect to nonparametric variables, followed by the Mann-Whitney ranked sum test for intergroup differences. Categorical variables were analyzed by using a series of 3 x 2
2 tests to determine differences among the three groups, followed by a 2 x 2
2 test or Fishers exact test, as appropriate, for intergroup differences. All follow-up analyses were corrected for the number of simultaneous contracts by using Bonferroni adjustments. A P value <0.05 was considered significant.
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| Discussion |
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5-HT3, or serotonin, is a neurotransmitter that is associated with a variety of clinical disorders, including nausea and vomiting (24). 5-HT3 receptors are widely distributed peripherally in the gastrointestinal tract and centrally in the nucleus tractus solitarius and area postrema (chemoreceptor trigger zone) (16,1416). Approximately 80% of the bodys total 5-HT3 is stored in the enterochromaffin cells of the gastrointestinal tract (2). 5-HT3 receptor antagonists exert their pharmacologic effects by competitive and selective binding to the 5-HT3 receptors and thus prevent agonism of the 5-HT3 receptors by 5-HT3 (16).
Several human studies suggest that emesis caused by chemotherapy and radiotherapy may be due to the release of 5-HT3 from the enterochromaffin cells of the gastrointestinal tract (24). 5-HT3, once liberated, binds to the 5-HT3 receptors at the gastrointestinal site; these receptors send impulses via vagal afferents to the nucleus tractus solitarius and then to the vomiting center, which causes emesis (14). 5-HT3 receptor antagonists are effective for this purpose and are considered most likely to exert their actions through the blockage of the 5-HT3 receptors from the peripheral site at the gastrointestinal tract, thus preventing the occurrence of nausea and vomiting (16).
For the prevention of PONV after general anesthesia, all 5-HT3 antagonists are also effective. Although 5-HT3 antagonists may bind to the 5-HT3 receptors located centrally or peripherally (16,1416), the exact mechanism by which 5-HT3 antagonists exert their actions in the prevention of PONV after general anesthesia has not been elucidated.
In this study, we questioned whether tropisetron, a 5-HT3 antagonist, has a significant central antiemetic action. Epidural morphine-related PONV was studied. It has been suggested that epidural morphine exerts an emetic action via the activation of opioid receptors in the chemoreceptor trigger zone, caused by cephalad migration of morphine. Therefore, if tropisetron has a significant central antiemetic action, it may effectively prevent the occurrence of PONV after epidural morphine. However, we did not find this, suggesting that tropisetron does not have a significant central antiemetic effect.
After a review of the literature, we found only two clinical studies that evaluated the central antiemetic effect of 5-HT3 antagonists (17,18). In these studies, either ondansetron 8 mg twice daily or tropisetron 5 mg once daily were used to prevent the occurrence of PONV after intrathecal morphine (0.3 mg). However, neither ondansetron nor tropisetron was effective for this purpose (17,18).
The dose of tropisetron used in our study was 5 mg. This dose was chosen because it is the dose recommended for prophylaxis of nausea and vomiting in patients receiving potent emetogenic drugs (e.g., cisplatin in chemotherapy) (14). For the prevention of PONV after general anesthesia, the recommended dose of tropisetron is smaller (2 mg for adult patients) (14).
Tropisetron caused a more frequent incidence of headache (26%) than the other two treatments. In direct comparisons of tropisetron with other 5-HT3 antagonists, the adverse event profiles of all 5-HT3 antagonists were very similar (2,3). Headache was the most frequently reported event, with reporting rates of 5%35% (2,3). However, the exact mechanism of this adverse event was not known.
Dexamethasone, a corticosteroid, is a potent antiemetic drug that exerts its antiemetic action though the blockage of the corticoreceptors in the nucleus tractus solitarius of the central nervous system (19). It is effective in reducing the incidence of emesis in patients undergoing chemotherapy (20,21). It is also effective in reducing the incidence of PONV after general anesthesia and after epidural morphine (9,10,21,22). The minimal effective dose is 5 mg for the prevention of PONV after general anesthesia and after epidural morphine (10,22). Our study is in agreement with this finding.
Tropisetron and dexamethasone did not influence the intensity of surgical pain. Both the severity of pain (VAS) scores and the number of patients requiring rescue analgesia were similar among groups. Tropisetron and dexamethasone did not influence the occurrence of pruritus related to epidural morphine.
In conclusion, IV tropisetron 5 mg did not prevent the occurrence of PONV associated with epidural morphine. IV dexamethasone 5 mg was effective for this purpose.
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This article has been cited by other articles:
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A. L Kovac Meta-Analysis of the Use of Rescue Antiemetics Following PONV Prophylactic Failure with 5-HT3 Antagonist/Dexamethasone Versus Single-Agent Therapies Ann. Pharmacother., May 1, 2006; 40(5): 873 - 887. [Abstract] [Full Text] [PDF] |
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J. B Leslie and T. J Gan Meta-Analysis of the Safety of 5-HT3 Antagonists with Dexamethasone or Droperidol for Prevention of PONV Ann. Pharmacother., May 1, 2006; 40(5): 856 - 872. [Abstract] [Full Text] [PDF] |
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