• Tia J M Sarén-Koivuniemi, Arvi M Yli-Hankala, and Mark J van Gils.
• University of Tampere, Medical School, Tampere, Finland.
• Comput Methods Programs Biomed. 2011 Nov 1;104(2):154-60.

ObjectiveAnalgesia is an important part of general anaesthesia, but no direct indicators of nociceptive-anti-nociceptive balance have been validated in detail. The Response Index of Nociception (RN) is a multiparameter approach which combines photoplethysmographic waveform (PPG), State Entropy (SE), Response Entropy (RE), and heart rate variability (HRV). We aimed at evaluating RN during general anaesthesia; especially we wanted to compare pre- and post-index values of certain noxious stimuli to the average index values. Our assumption was that RN could be a useful indicator of nociceptive-anti-nociceptive balance during the surgery.MethodsSixty women undergoing gynaecological or breast surgery participated in the study. All patients had elective surgery and anaesthesia was maintained with propofol-remifentanil target controlled infusion. Neuromuscular blocking agent rocuronium was used at the beginning of the surgery. Electrocardiography (ECG), photoplethysmography (PPG) and electroencelophalography (EEG) were registered and extracted off-line. An index, reflecting amplitude and frequency of occurrence of abrupt increases ("peaks") in the RN was evaluated during surgery in general and around occurrences of predefined noxious stimuli in particular.ResultsFifty-four patients were eligible for analysis. Patient movement was associated with increased index values, both before and after the event. Post-event values of the index for intubation and skin incision were higher than its intra-surgery baseline, while pre-event values remained unchanged.ConclusionChanges in RN can be used to detect noxious stimuli during surgery. RN also predicted movement in our patients under propofol-remifentanil anaesthesia.Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

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