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Predicting personalised remifentanil effect site concentration for surgical incision using the nociception level index

September 22, 2022

BACKGROUND
Inadequate antinociception can cause hae- modynamic instability. The nociception level (NOL) index measures response to noxious stimuli, but its capacity to predict optimal antinociception is unknown.
OBJECTIVE
To determine if NOL index change to a tetanic stimulus in cardiac and noncardiac surgery patients could predict the required remifentanil concentration for haemo- dynamic stability at skin incision.
DESIGN A prospective two-phase cohort study.
SETTING University hospital.
PATIENTS Patients undergoing remifentanil-propofol target controlled infusion (TCI) anaesthesia.
INTERVENTIONS
During the calibration phase, investigators evaluated the tetanic stimulus induced NOL index change under standardised TCI remifentanil-propofol anaesthesia during a no- touch period [bispectral index (BIS) between 40 and 60, NOL index under 15]. If the NOL index change was 20 or greater following tetanic stimulation, investigators repeated the tetanus at higher remifentanil concentrations until the response was blunted. Surgeons incised the skin at this remifentanil concen- tration. The investigators derived a prediction model and in the validation phase calculated, using the NOL response to a single tetanus, the required incision remifentanil concentration for the start of surgery.
INTERVENTIONS
Haemodynamic stability at incision [i.e. maximum heart rate (HR) < 20% increase from baseline, minimum HR (40 bpm) and mean arterial pressure (MAP)  <20% of baseline]. RESULTS
During the calibration phase, no patient had hypertension. Two patients had a HR increase slightly great- er than 20% (25.4 and 26.7%) within the first 2 min of surgery, but neither of these two patients had a HR above 76 bpm. Two patients were slightly hypotensive after incision (MAP 64 and 73 mmHg). During the validation phase, neither tachycardia nor hypotension occurred, but MAP increased to 21.5% above baseline for one patient.
CONCLUSION
During a no-touch period in patients under steady-state general anaesthesia [propofol effect site con- centration (Ce) required for BIS between 40 and 60], the NOL index response to a tetanic stimulus under remifentanil antinociception can be used to personalise remifentanil Ce for the start of surgery and ensure stable haemodynamics.