BACKGROUND: Monitored anesthesia care (MAC) has become increasingly important as a means of ensuring patient comfort, safety and satisfaction during surgery under local anesthesia. The purpose of this study was to evaluate the effect of monitored anesthesia care using alfentanil and ketorolac in patients undergoing endoscopic sinus surgery (ESS). METHODS: We studied 47 adult patients premedicated with glycopyrrolate 0.2 mg and midazolam 0.02 mg/kg IV. Using a 5.0 endotracheal tube, 5 L/min of oxygen was delivered via mouth. A mixture of 30 mg of ketorolac and 2,500microgram of alfentanil in 25 ml of saline was infused to patients at a rate of 1microgram/kg/min alfentanil after a bolus injection of 5microgram/kg alfentanil before operation. During operations we monitered vital signs, SpO2, OAA/S (Observer's Assessment of Alertness/Sedation) scale and BIS scores. Six hours postoperatively we assessed patient degree of satisfaction via NRS (1-10) with the anesthetic technique and side effects. RESULTS: Mean duration of drug infusion was 35 +/- 10.1 min, and the mean infusion rate of alfentanil was 1.09 +/- 0.23microgram/kg/min. Significant differences were observed between OAA/S scale scores at 10 min and 30 min after drug infusion and those in the waiting room (4.63, 4.65 vs 5, P <0.05)(Fig. 4). The mean patient satisfaction score was 8.3 out of 10, and 93.6% (44/47) of patients said they would recommend this anesthetic technique to others for ESS. CONCLUSIONS: Our results suggest that MAC using a mixture of alfentanil and ketorolac during ESS is a good way of relieving patient anxiety and pain without respiratory depression or excessive sedation. This study also showed a high level of patient satisfaction for those undergoing ESS under local anesthesia.