The Narcotrend Index Indicates Age-Related Changes During Propofol Induction in Children

Electroencephalographic Indices for Clinical Endpoints during Propofol Anesthesia in Infants: An Early-phase Propofol Biomarker-finding Study

BACKGROUND

Unlike expired sevoflurane concentration, propofol lacks a biomarker for its brain effect site concentration, leading to dosing imprecision particularly in infants. Electroencephalography monitoring can serve as a biomarker for propofol effect site concentration, yet proprietary electroencephalography indices are not validated in infants. The authors evaluated spectral edge frequency (SEF95) as a propofol anesthesia biomarker in infants. It was hypothesized that the SEF95 targets will vary for different clinical stimuli and an inverse relationship existed between SEF95 and propofol plasma concentration.

METHODS

This prospective study enrolled infants (3 to 12 months) to determine the SEF95 ranges for three clinical endpoints of anesthesia (consciousness-pacifier placement, pain-electrical nerve stimulation, and intubation-laryngoscopy) and correlation between SEF95 and propofol plasma concentration at steady state. Dixon's up-down method was used to determine target SEF95 for each clinical endpoint. Centered isotonic regression determined the dose-response function of SEF95 where 50% and 90% of infants (ED50 and ED90) did not respond to the clinical endpoint. Linear mixed-effect model determined the association of propofol plasma concentration and SEF95.

RESULTS

Of 49 enrolled infants, 44 evaluable (90%) showed distinct SEF95 for endpoints: pacifier (ED50, 21.4 Hz; ED90, 19.3 Hz), electrical stimulation (ED50, 12.6 Hz; ED90, 10.4 Hz), and laryngoscopy (ED50, 8.5 Hz; ED90, 5.2 Hz). From propofol 0.5 to 6 μg/ml, a 1-Hz SEF95 increase was linearly correlated to a 0.24 (95% CI, 0.19 to 0.29; P < 0.001) μg/ml decrease in plasma propofol concentration (marginal R2 = 0.55).

CONCLUSIONS

SEF95 can be a biomarker for propofol anesthesia depth in infants, potentially improving dosing accuracy and utilization of propofol anesthesia in this population.

EDITOR’S PERSPECTIVE

Correlation of Comfort Score and Narcotrend Index during Procedural Sedation with Midazolam and Propofol in Children

Background/Objectives: Precise assessment of hypnotic depth in children during procedural sedation with preserved spontaneous breathing is challenging. The Narcotrendindex (NI) offers uninterrupted information by continuous electrocortical monitoring without the need to apply a stimulus with the risk of assessment-induced arousal. This study aimed to explore the correlation between NI and the Comfort Scale (CS) during procedural sedation with midazolam and propofol and to identify an NI target range for deep sedation. Methods: A prospective observational study was conducted on 176 children (6 months to 17.9 years) undergoing procedural sedation with midazolam premedication and continuous propofol infusion. Statistical analyses included Pearson correlation of NI and CS values, logistic regression, and receiver operating curves. Results: Median NI values varied with CS and age. The correlation coefficient between CS and NI was 0.50 and slightly higher in procedure-specific subgroup analyses. The optimal NI cut-off for deep sedation was between 50 and 60 depending on the analyzed subgroup and displayed high positive predictive values for sufficient sedation throughout. Conclusion: Our study found a moderate correlation between NI and CS, demonstrating reliable identification of adequately sedated patients.

A comparative study on adequate anesthesia depth: clinical judgement and the Narcotrend® measurement

Purpose

To compare the clinical judgement of electroencephalogram (EEG)-naïve anesthesiologists with an EEG-based measurement of anesthetic depth (AD) using the Narcotrend® monitor.

Methods

In this prospective cohort study including 600 patients, AD during stable anesthesia was assessed by clinical judgement of the attending, EEG-blinded anesthesiologist (using a scale staging the AD as mid-adequate, adequate but fairly deep, or adequate but fairly light) and by simultaneously recorded Narcotrend measurements.

Results

In 42% of patients (n = 250), the anesthesiologist’s clinical judgement was in agreement with anesthetic levels as measured by the Narcotrend monitor. In 46% of patients (n = 274), the anesthesiologist’s judgement and the Narcotrend monitor differed by one AD level (minor discordance). Major discordance was observed in 76 (13%) measurements (judged deeper than measured, n = 29 [5%]; judged lighter than measured, n = 47 [8%]). In 7% of patients (n = 44), the Narcotrend index was outside the limits of adequate AD (too deep, n = 28 [5%]; too superficial, n = 16 [3%]). The overall level of agreement between the anesthesiologist’s judgement and the Narcotrend monitor was not statistically significant (Cohen’s kappa, −0.039; P = 0.17). Using a random forests algorithm, age, mean blood pressure, the American Society of Anesthesiologists classification, body mass index, and frailty were the variables with the highest relative feature importance to predict the level of agreement.

Conclusion

These results suggest that clinical judgement of AD during stable anesthesia was not in agreement with EEG-based assessment of anesthetic depth in 58% of cases. Nevertheless, this finding could be influenced by the lack of validated scales to clinically judge AD.

Trial registration

www.clinicaltrials.gov (NCT02766894); registered 10 May, 2016.

Practicalities of Total Intravenous Anesthesia and Target-controlled Infusion in Children

Propofol administered in conjunction with an opioid such as remifentanil is used to provide total intravenous anesthesia for children. Drugs can be given as infusion controlled manually by the physician or as automated target-controlled infusion that targets plasma or effect site. Smart pumps programmed with pharmacokinetic parameter estimates administer drugs to a preset plasma concentration. A linking rate constant parameter (keo) allows estimation of effect site concentration. There are two parameter sets, named after the first author describing them, that are commonly used in pediatric target-controlled infusion for propofol (Absalom and Kataria) and one for remifentanil (Minto). Propofol validation studies suggest that these parameter estimates are satisfactory for the majority of children. Recommended target concentrations for both propofol and remifentanil depend on the type of surgery, the degree of surgical stimulation, the use of local anesthetic blocks, and the ventilatory status of the patient. The use of processed electroencephalographic monitoring is helpful in pediatric total intravenous anesthesia and target-controlled infusion anesthesia, particularly in the presence of neuromuscular blockade.

Intraoperative target-controlled infusion anesthesia application using remifentanil hydrochloride with etomidate in patients with severe burn as monitored using Narcotrend

OBJECTIVE

This study aims to evaluate the feasibility of intraoperative composite target-controlled infusion (TCI) anesthesia application using remifentanil hydrochloride with etomidate in patients with severe burns, as monitored by Narcotrend.

METHODS

A total of 40 patients with severe burns with eschar excisions and skin grafts were randomly and equally grouped into the etomidate (E) and the propofol groups (P). Anesthesia was induced and maintained by a remifentanil hydrochloride TCI combined with etomidate or propofol. The depth of anesthesia and other relevant indicators were recorded through intraoperative electroencephalogram monitoring using a Narcotrend monitor.

RESULTS

No statistically significant differences were observed between the drug withdrawal times, eye opening requirements, or orientation recoveries of the two groups (P>0.05). The cortisol and aldosterone levels in group E were significantly lower than those in group P 24h post operation (P<0.05). No significant differences between the number of operations, hospitalization duration, mean arterial pressure, heart rate, and postoperative adverse reaction incidence of the two groups were observed at each time point (P>0.05).

CONCLUSION

The application of a composite remifentanil hydrochloride combined with etomidate TCI is feasible for the early eschar excision in patients with severe burns.

Evolution of electroencephalogram signal analysis techniques during anesthesia

Biosignal analysis is one of the most important topics that researchers have tried to develop during the last century to understand numerous human diseases. Electroencephalograms (EEGs) are one of the techniques which provides an electrical representation of biosignals that reflect changes in the activity of the human brain. Monitoring the levels of anesthesia is a very important subject, which has been proposed to avoid both patient awareness caused by inadequate dosage of anesthetic drugs and excessive use of anesthesia during surgery. This article reviews the bases of these techniques and their development within the last decades and provides a synopsis of the relevant methodologies and algorithms that are used to analyze EEG signals. In addition, it aims to present some of the physiological background of the EEG signal, developments in EEG signal processing, and the effective methods used to remove various types of noise. This review will hopefully increase efforts to develop methods that use EEG signals for determining and classifying the depth of anesthesia with a high data rate to produce a flexible and reliable detection device.

Monitoring the depth of anaesthesia

One of the current challenges in medicine is monitoring the patients’ depth of general anaesthesia (DGA). Accurate assessment of the depth of anaesthesia contributes to tailoring drug administration to the individual patient, thus preventing awareness or excessive anaesthetic depth and improving patients’ outcomes. In the past decade, there has been a significant increase in the number of studies on the development, comparison and validation of commercial devices that estimate the DGA by analyzing electrical activity of the brain (i.e., evoked potentials or brain waves). In this paper we review the most frequently used sensors and mathematical methods for monitoring the DGA, their validation in clinical practice and discuss the central question of whether these approaches can, compared to other conventional methods, reduce the risk of patient awareness during surgical procedures.