Opioids remain the cornerstone for perioperative analgesia, albeit frequently associated with side effects. Most of these side-effects are dose-dependent. Thus intra-operative monitors are necessary to measure the balance between Nociception and Anti-Nociception (NAN balance) by an adequate opioid administration. Recently the NOL monitor was released.The NoL index ranges from 0 to 100 and is based on a nonlinear combination of nociception-related physiologic variables, specifically heart rate (HR), heart rate variability at the 0.15- to 0.4-Hz band power, photoplethysmograph wave amplitude (PPGA), skin conductance level, number of skin conductance fluctuations, and their time derivatives. The NoL index estimates the nociceptive/antinociceptive state from these component measures using random forest regression. In our department, a combination of TCI propofol (Schnider model) and remifentanil (Minto model) is used to for most of the anaesthetic procedures, including cardiac anaesthesia. Remifentanil is titrated to prevent an increase in blood pressure and hearth rhythm at noxious stimuli, such as surgical incision, and adapted following hemodynamic trend during surgery. The hypothesis of this study is to develop a calibration test using the NOL index variation to define the individual most appropriate NAN balance using remifentanil TCI before the start of surgery and before a very strong noxious surgical stimulus such as surgical incision in non-cardiac and cardiac surgery. Before the start of surgery, the investigators want to titrate in each patient the remifentanil Ce required to abolish the NOL index response to a calibrated noxious tetanic stimulus (Tetanus 60 mamp, 100 Hz, 30 seconds). Thus this individual remifentanil Ce will be the remifentanil level programmed before surgical incision. NOL and hemodynamic responses will be recorded during the entire duration of surgery. Study protocol amendment: validation of the calibration study: Data from the calibration phase will be used to derive a formula to predict individualised anti-nociception for incision.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
36
After tracheal intubation, a Tetanus test (60 mAmp,100 Hz) is done during 30 sec at remifentanil level Ce of 4 ng/ml (with starting NOL value \<10). According to the NOL response: increment of 1 ng/ml of RemiCe if NOL gradient ≥ 20 / decrement of 1 ng/ml of remifentanil Ce NOL gradient \< 10. During the testing period propofol Ce is fixed at the concentration associated with BIS levels between 45-60 during the first calibration. Upon the incision and 2 minutes after skin incision, Propofol TCI (Schnider model) is adjusted to BIS between 45-60 and remifentanil Ce at which the variation of NOL index variation is less than10 units at a NOL starting value \<10. MAP (mean arterial pressure), HR (heart rhythm) and NIBP (non-invasive blood pressure) will be measured. The formula derived from the calibration phase will be tested during a single tetanic stimulation at remifentanil Ce of 4 ng/ml during the validation phase.
Erasme Hospital
Brussels, Belgium
Predictive value of NOL
A calibration Tetanus test of 60 mAmp during 30 sec at remifentanil level (Ce) of 4 ng/ml will be done when starting NOL is below 10. According to the NOL response: there will be an increment of 1 ng/ml of RemiCe if NOL gradient ≥ 10 or a decrement of 1 ng/ml of remifentanil Ce NOL gradient \< 10. The optimal individual remifentanil level is defined as the level at which the variation of NOL index will be less than 10 units starting at a NOL value below 10. So surgical incision will be done at 'optimal individual remifentanil level' and MAP (mean artrial pressure), HR (heart rhythm), NIBP (non-invasive blood pressure) will be measured (every 3 minutes).
Time frame: intra-operative
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