No clinical evidence of acute opioid tolerance after remifentanil-based anaesthesia

We have prospectively assessed whether remifentanil-based anaesthesia is as sociated with clinically relevant acute opioid tolerance, expressed as grea ter postoperative pain scores or morphine consumption. Sixty patients under going elective gynaecological, non-laparoscopic, surgery were randomly assi gned to receive remifentanil (group R, n=30) or sevoflurane (group S, n=30) based anaesthesia. Postoperative analgesia was provided with morphine thro ugh a patient-controlled infusion device. Mean (SD) remifentanil infusion r ate in group R was 0.23 (0.10) mug kg(-1) min(-1) and mean inspired fractio n of sevoflurane in group S was 1.75 (0.70)%. Mean (SD) cumulative morphine consumption during the first 24 postoperative hours was similar between gr oups: 28.0 (14.2) mg (group R) vs 28.6 (12.4) mg (group S). Pain scores, we re also similar between groups during this period. These data do not suppor t the development of acute opioid tolerance after remifentanil-based anaest hesia in this type of surgery.