目的：评估地塞米松对新辅助化疗（术前化疗）后乳腺癌改良根治术术后恶心呕吐（postoperative nausea and vomiting, PONV）的预防效果。方法：新辅助化疗后行乳腺癌改良根治术的女性乳腺癌患者280例，18~60岁，随机分为两组，每组140例：（1）D组：实验组，术前给予10 mg地塞米松静脉滴注；（2）C组：对照组，术前给予2 mL生理盐水作为安慰剂静脉滴注。每组患者再分为两亚组，每组70例，分别应用丙泊酚全凭静脉麻醉(total intravenous anesthesia, TIVA)（P亚组）和七氟醚维持吸入全身麻醉（S亚组）。所有患者均进行标准的全身麻醉操作，手术结束前30 min静脉滴注昂丹司琼(ondansetron) 8 mg。随访术后24 h内患者恶心呕吐的发生率，并对PONV的影响因素进行Logistic回归分析。检测因素包括年龄、体重指数（body mass index, BMI）、手术时间、术后疼痛程度、晕动病史/既往PONV史、是否应用地塞米松以及麻醉方法。结果：术后24 h内D组患者恶心呕吐的发生率明显低于C组患者（11.4% vs. 20.7%，P=0.034）；术后0~2 h D组患者PONV的发生率低于C组患者（1.4% vs. 6.4%，P=0.031）；术后2~24 h D组患者PONV的发生率与C组患者差异无显统计学意义（10.7% vs. 17.9%，P=0.088）。术后24 h内各时段，D组与C组内丙泊酚全凭静脉麻醉亚组与吸入麻醉亚组PONV的发生率比较差异均无统计学意义（P>0.05）。Logistic回归分析显示地塞米松对新辅助化疗后乳腺癌改良根治术患者术后恶心呕吐有预防效果（OR=0.447，P=0.030），晕动症/PONV病史是术后恶心呕吐的危险因素（OR=15.730，P＜0.001）。结论：术前应用地塞米松可明显降低新辅助化疗后乳腺癌改良根治术患者术后恶心呕吐的发生率。

Objective：To evaluate the influence of dexamethasone on the incidence of postoperative nausea and vomiting (PONV) in patients undergoing modified radical mastectomy with neoadjuvant chemotherapy. Methods:In a prospective trial, 280 female (18-60 years) breast cancer patients undergoing modified radical mastectomy with neoadjuvent chemotherapy were randomized to two groups: one with dexamethasone (Group D) and one without dexamethasone (Group C, n=140). In each group, anesthesia was maintained with volatile anesthesia or total intravenous anesthesia (TIVA): TIVA (propofol) without dexamethasone (Subgroup CP); volatile anesthesia (sevoflurane) without dexamethasone (Subgroup CS); TIVA with 10 mg dexamethasone intravenously before anesthetic induction (Subgroup DP); volatile anesthesia with 10 mg dexamethasone intravenously before anesthetic induction (Subgroup DS). A standard general anesthetic technique was used. All the patients received 8 mg of ondansetron intravenously 30 minutes before the end of surgical procedures. The incidence of PONV during the 24-hour postoperative period was recorded. A Logistic regression analysis was conducted to examine relevant factors for PONV . The tested factors were: age, body mass index (BMI), duration of surgery, postoperative pain, history of motion sickness/PONV, with or without dexamethasone and anesthetic regimen.Results:There was a significant lower incidence of PONV in the patients who received dexamethasone than in those who received placebo during the 24-hour postoperative period (11.4% vs. 20.7%，P=0.034). In the early postoperative period (0-2 h) dexamethasone reduced the incidence of PONV ( 1.4%vs.6.4%， P=0.031）,but in the late postoperative period (2-24 h) the difference of the incidence was insignificantly (10.7% vs. 17.9%， P=0.088). No differences were found between TIVA and volatile anesthesia in the 24hour postoperative period. Dexamethasone was effective to prevent PONV（OR=0.447，P=0.030）, and history of PONV or motion sickness was the risk factor of PONV (OR=15.730，P＜0.001). Conclusion:Dexamethasone prevents PONV effectively in patients undergoing modified radical mastectomy with neoadjuvant chemotherapy, and TIVA cannot decrease the incidence of PONV in the 24hour postoperative period in those patients.