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584Among 1,236 patients studied, 15 patients were excluded because they were transferred to the non-gynecological ward and data on NRS nausea scores were lacking. Therefore, data from 1,221 patients were analyzed. Patients’ demographic, anesthetic, and surgical characteristics, and drugs used perioperatively are summarized in Table 1.The results of the univariate and multivariate logistic regression analyses to examine effects of above-mentioned nine covariates on the develop-ment of PONV are summarized in Table 2. The univariate logistic regression analysis revealed that age (including 31 patients aged ≥ 50 years), BMI, smoking habits (had by 85 patients), or the method of general anesthesia (TIVA in 25 patients versus inhalation anesthesia in 1,196 patients) was not associated with or did not tend to be associated with the incidence of PONV (p > 0.1 for each), while the use of prophylactic antiemetics given in 136 patients (metoclopramide in 96 patients and droperidol in 40 patients), the use of the reversal agent for muscle relaxants (neostigmine [2 mg] co-administrated with atropine [1 mg]) given in 494 patients, postoperative uses of rescue opioid analgesics other than PCA fentanyl given in 208 patients (pentazocine, fentanyl, buprenorphine, and pethidine in 99, 79, 16, and 14 patients, respec-tively), and intravenous fentanyl PCA, including no use of PCA in 221 patients, the use of fentanyl PCA without droperidol in 616 patients, and the use of fentanyl PCA with droperidol in 384 patients, were significantly associated with the incidence of PONV (p < 0.05 for each), and duration of anesthesia tended to be associated with the incidence of PONV (p = 0.0689). However, the multivariate logistic regression analysis employing these nine covari-ates revealed that only three covariates, including duration of anesthesia, the use of the reversal agent, and the use or no use of fentanyl PCA with or without droperidol were significantly associated with the incidence of PONV (p < 0.05 for each). A longer duration of anesthesia (in hours) was asso-ciated with the increased incidence of PONV (odds ratio [OR], 1.170; 95% confidence interval [CI], 1.000-1.360; p = 0.0467). The use of the reversal agent was associated with the lower incidence of PONV (OR, 0.746; 95% CI, 0.585-0.950; p = 0.0177). No use of PCA and the use of fentanyl PCA without droperidol were associated with the higher inci-dence of PONV, compared with the use of fentanyl PCA with droperidol (OR, 1.810; 95% CI, 1.250-2.640; p = 0.0019; and OR, 2.500; 95% CI, 1.880-3.310; p < 0.0001, respectively), and the use of fentanyl PCA without droperidol tended to be associated with the higher incidence of PONV, compared with no use of PCA (OR, 1.380; 95% CI, 0.988-1.920; p = 0.0592). Rescue analgesics and rescue antiemetics used postoperatively and the incidence of PONV according to differences in the use of fentanyl PCA are shown in Table 3. In the total cohort, the actual incidence of PONV that developed until nine hours after the return to the gynecological ward was 47.3% (577/1221) (Tables 1 & 3). Regarding intra-venous fentanyl PCA, the actual incidences of PONV were 32.3% (124/384) in patients receiving fentanyl PCA with droperidol, 47.5% (105/221) in patients not receiving PCA, and 56.5% (348/616) in patients receiving fentanyl PCA without droperidol (Table 3). The chi-square test revealed that the incidence of PONV was lower in patients receiving fentanyl PCA with droperidol than those not receiving PCA (p = 0.0005) and those receiving fentanyl PCA without droperidol (p < 0.0001), and also was lower in patients not receiving PCA than those receiving fentanyl PCA without droperidol (p = 0.0227), almost in good agreement with results of logistic regression analyses. Postoperative rescue opioids were used in 6.8% (26/384) of patients receiving fentanyl PCA with droperidol, 14.3% (88/616) of patients receiving fentanyl PCA without droperidol, and 42.5% (94/221) of patients not receiving PCA (Table 3). The chi-square test revealed that rescue opioids were used more frequently in patients not receiving PCA than those receiving fentanyl PCA without droperidol (p < 0.0001), and in patients receiving fentanyl PCA without droperidol than those receiving fentanyl PCA with droperidol (p = 0.0003). The chi-square test revealed that actual inci-dence of PONV was significantly lower in patients receiving the reversal agent (41.9% [207/494]) than those not receiving this agent (50.9% [370/727]) (p = 0.0020) in agreement with results of logistic regression analyses. Results