Monitoring: Equipment and Computers
Background: The qCON algorithm (Quantium Medical, Spain) was recently introduced as an index to assess the level of hypnosis (1) during sedation-analgesia. It is calculated from the raw EEG using technology based on Adaptive Neuro Fuzzy Inference Systems (ANFIS). ANFIS is a data driven approach, rather than assuming an underlying function governing the relationship between input and output. In this study, EEG data from a previous study (2) were replayed with the qCON algorithm for the assessment of the level of consciousness during general anesthesia.
Methods: 20 female patients (aged 32±5 y, mean±std), scheduled for ambulatory gynecologic surgery, were enrolled after obtaining approval from the Institutional Ethics Committee (2). A computer-assisted continuous-infusion device was used to infuse propofol to a target effect-site concentration, using the model published by Schnider et al (3). The initial propofol target effectsite concentration (CePROP) was set at 1.5 μg/ml and was increased every 4 min by 0.5 μg/ml until loss of all relevant clinical signs. BIS, AAI, level of consciousness (using the OAAS score and the response to eyelash reflex), and reaction to noxious stimulus were recorded before each increase in target concentration. The qCON was calculated offline from the raw EEG. A total of 168 measurements of OAAS, eyelash reflex and reaction to noxious stimuli were considered. The prediction probability (mean(SE)), Pk, of the different indicators to describe OAAS, loss of eyelash reflex, and response to noxious stimulus was calculated.
Results and Discussion: Table 1 shows the Pk values of BIS, AAI, CePROP and qCON in the prediction of the OAAS, loss of eyelash reflex, and loss of response to noxious stimulus.
Conclusion: The qCON performed as well as BIS, AAI and CePROP for predicting the three clinical signs, OAAS, loss of eyelash reflex and reaction to noxious stimulus. Therefore, qCON can be used as an accurate indicator for the level of sedation and loss of consciousness during propofol anaesthesia.
1. Valencia et al., abstract in ASA 2012 2. Struys et al. Anesthesiology 2002;96:803-16. 3. Schnider et al. Anesthesiology 1998;88:1170-82