Predicting acute postoperative pain by the Qnox score at the end of surgery: a prospective observational study

The QNox score (Quantium Medical S.L., distributed by Fresenius Kabi) has recently been introduced as a tool to quantify intraoperative analgesia. Being based on the analysis of electroencephalographic data, QNox is distinctly different to other methods of nociception monitoring that rely almost entirely on the assessment of sympathetic activity. However, there are currently no published data to validate use of QNox in a clinical setting. We investigated the value of pre-arousal QNox data at the end of surgery for prediction of acute postoperative pain in the PACU. A total of 150 patients scheduled for non-emergency surgery under sevoflurane-opioid general anaesthesia were included in the study. At the end of surgery but before patient arousal, QNox was measured minutely for 5 min. After admission to the recovery room, pain scores (numeric rating scale [NRS], 0–10) were obtained 5 minutely for 15 min. Data from 144 patients were analysed. QNox before arousal showed no correlation (ρ=0.057) with acute postoperative pain in the PACU. Furthermore, the score was found to have no value for the prediction of acute postoperative pain (area under the receiver operating curve, 0.501; 95% confidence interval, 0.406–0.597). QNox at the end of surgery before arousal showed no association with and allowed no prediction of acute pain in the PACU. ACTRN12618001662257.