Background and Goal of Study: Continual remifentanil use in anesthesia is related with postoperative hyperalgesia and opioid tolerance. Study investigate whether lowering remifentanil dose at the end of surgery impact on pain decrease, need for rescue analgesics and nausea appearance in postoperative period.
Materials and methods: Twenty five female patients, ASA 2 class, underwent brest conserving surgery in general anaesthesia, between January and October 2015. Anesthesia was induced with propofol and remifentanil. Anesthesia was maintained with propofol and with remifentanil in dose: group A (13/25) fixed dose: 0.4mcg/kg/min to the end of surgery, and in group B (12/25) from last 30 minutes of surgery, on every 10 minutes, remifentanil was gradually lowered from 0.4 to finally 0.1 mcg/kg/min. Tradamol 100 mg intravenously was given in both groups 15 min before end of surgery. Ketorolac was rescue analgesic. Pain score after arm movement and in rest (VAS and modified VAS), postoperative nausea and vomiting was followed in first 24h. Fisher´s exact test and Wilcoxon rank sum test with continuity correction are used to test differences between groups.
Results and discussion: Average patients age 48.67, average BMI 24,20. A group (52%), average age 49.1, average BMI 24.07, B group (48%), average age 47.4 and BMI 24.50. Average surgery time was 81.9 min. There was statistically significant decrease in average pain score after arm movement and in rest in first 24 h between gruop B and A (2.07 vs. 4.0, p < 0.05) and (1.04 vs. 3.0, p < 0.05). Rescue analgesic use in first postoperative hour, in B vs A group was 1 vs 3 patients, p< 0,01. One hour after dose of rescue analgesics pain score was B vs. A group 0 vs. 0.6, p < 0.05. Nausea in 24h in B vs. A was 1.20 vs 3.40, p < 0.01.
Conclusion(s): Gradual lowering of remifentanil 30 minutes before end of surgery significantly decreased pain score, nausea and use of rescue analgesics. 
References: 
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Impact of remifentanil application modality on postoperative pain after brest conserving surgery