Statistical Analysis Plan for "An international multicenter study of isoelectric electroencephalography events in infants and young children during anesthesia for surgery"

Isoelectric Electroencephalography in Infants and Toddlers During Anesthesia for Surgery-an International Observational Study

BACKGROUND

Intraoperative isoelectric electroencephalography (EEG) has been associated with hypotension and postoperative delirium in adults. This international prospective observational study sought to determine the prevalence of isoelectric EEG in young children during anesthesia. We hypothesized that the prevalence of isoelectric events would be common worldwide and associated with certain anesthetic practices and intraoperative hypotension.

METHODS.

Fifteen hospitals enrolled patients age ≤ 36 months for surgery using sevoflurane or propofol anesthetic. Frontal 4-channel EEG was recorded for isoelectric events. Demographics, anesthetic, emergence behavior, and Pediatric Quality of Life (PedsQL) variables were analyzed for association with isoelectric events.

RESULTS.

Isoelectric events occurred in 32% (206/648) of patients, varied significantly among sites (9-88%), and were most prevalent during pre-incision (117/628, 19%) and surgical maintenance (117/643, 18%). Isoelectric events were more likely with [odds ratio-OR (95% confidence interval-CI)] infants < 3 months [4.4 (2.57-7.4) p<0.001], endotracheal tube use [1.78 (1.16-2.73) p=0.008], propofol bolus for airway placement after sevoflurane induction [2.92 (1.78-4.8) p<0.001], and less likely with use of muscle relaxant for intubation [0.67 (0.46-0.99) p=0.046]. Expired sevoflurane was higher in patients with isoelectric events [mean difference (95% CI)] during pre-incision [0.2% (0.1, 0.4) p=0.005] and surgical maintenance [0.2% (0.1, 0.3) p=0.002]. Isoelectric events were associated with moderate (8/12, 67%) and severe hypotension (11/18, 61%) during pre-incision [OR: 4.6 (1.30-16.1) p=0.018; 3.54 (1.27, 9.9) p=0.015] and surgical maintenance [OR: 3.64 (1.71-7.8) p=0.001; 7.1 (1.78- 28.1) p=0.005], and lower PedsQL scores [median of differences (95% CI)] at baseline in patients 0-12 [-3.5 (-6.2, -0.7) p=0.008] and 25-36 months [-6.3 (-10.4, -2.1) p=0.003] and 30-day follow-up in 0-12 months [-2.8 (-4.9, 0) p=0.036]. Isoelectric events were not associated with emergence behavior or anesthetic (sevoflurane vs propofol).

CONCLUSIONS.

Isoelectric events were common worldwide in young children during anesthesia and associated with age, specific anesthetic practices, and intraoperative hypotension.

Applications and Limitations of Neuro-Monitoring in Paediatric Anaesthesia and Intravenous Anaesthesia: A Narrative Review

Safe management of anaesthesia in children has been one of the top areas of research over the last decade. After the large volume of articles which focused on the putative neurotoxic effect of anaesthetic agents on the developing brain, the attention and research efforts shifted toward prevention and treatment of critical events and the importance of peri-anaesthetic haemodynamic stability to prevent negative neurological outcomes. Safetots.org is an international initiative aiming at raising the attention on the relevance of a high-quality anaesthesia in children undergoing surgical and non-surgical procedures to guarantee a favourable outcome. Children might experience hemodynamic instability for many reasons, and how the range of normality within brain autoregulation is maintained is still unknown. Neuro-monitoring can guide anaesthesia providers in delivering optimal anaesthetic drugs dosages and also correcting underling conditions that can negatively affect the neurological outcome. In particular, it is referred to EEG-based monitoring and monitoring for brain oxygenation.

An approach to using pharmacokinetics and electroencephalography for propofol anesthesia for surgery in infants

Safe and effective techniques for propofol total intravenous anesthesia (TIVA) in infants are not well imbedded into clinical practice, resulting in practitioner unfamiliarity and potential for over- and under-dosing. In this education article, we describe our approach to TIVA dosing in infants and toddlers (birth to 36 months) which combines the use of pharmacokinetic models with EEG multi-parameter analysis. Pharmacokinetic models describe propofol and remifentanil effect site concentrations (Ce) over time in different age groups for a given dosing regimen. These models display substantial biological variability between individuals within age groups, impeding their application to clinical practice. Nevertheless, they reveal that younger infants require a higher propofol loading dose, a lower propofol maintenance dose, and a higher remifentanil dose compared with older infants. Proprietary EEG indices (eg, Bispectral Index) can serve as a biomarker of propofol Ce in adults and children to guide dosing to the individual patient; however, they are not recommended for infants as their validity remains uncertain this population. In our experience, EEG waveforms and processed parameters can reflect propofol Ce in infants, reflected by spectral edge frequency (SEF), density spectral array (DSA), and waveform patterns. In our practice, we use a "lookup table" of age-based dosing regimens or target-controlled infusion (TCI) based on the pharmacokinetic models to deliver a target propofol Ce and co-administer remifentanil and/or regional technique for analgesia. We analyze Electroencephalogram (EEG) waveforms, SEF, and DSA to adjust the propofol dose or TCI target concentration to the individual infant. EEG analysis mitigates against biological variability inherent in the pharmacokinetic models and has improved our experience with TIVA for infants.

Electroencephalographic features of discontinuous activity in anesthetized infants and children

Background

Discontinuous electroencephalographic activity in children is thought to reflect brain inactivation. Discontinuity has been observed in states of pathology, where it is predictive of adverse neurological outcome, as well as under general anesthesia. Though in preterm-infants discontinuity reflects normal brain development, less is known regarding its role in term children, particularly in the setting of general anesthesia. Here, we conduct a post-hoc exploratory analysis to investigate the spectral features of discontinuous activity in children under general anesthesia.

Methods

We previously recorded electroencephalography in children less than forty months of age under general anesthesia (n = 65). We characterized the relationship between age, anesthetic depth, and discontinuous activity, and used multitaper spectral methods to compare the power spectra of subjects with (n = 35) and without (n = 30) discontinuous activity. In the subjects with discontinuous activity, we examined the amplitude and power spectra associated with the discontinuities and analyzed how these variables varied with age.

Results

Cumulative time of discontinuity was associated with increased anesthetic depth and younger age. In particular, age-matched children with discontinuity received higher doses of propofol during induction as compared with children without discontinuity. In the tens of seconds preceding the onset of discontinuous activity, there was a decrease in high-frequency power in children four months and older that could be visually observed with spectrograms. During discontinuous activity, there were distinctive patterns of amplitude, spectral edge, and power in canonical frequency bands that varied with age. Notably, there was a decline in spectral edge in the seconds immediately following each discontinuity.

Conclusion

Discontinuous activity in children reflects a state of a younger or more deeply anesthetized brain, and characteristic features of discontinuous activity evolve with age and may reflect neurodevelopment.

Neuromonitoring in paediatric anaesthesia

PURPOSE OF REVIEW

There has been a steady advance in neuromonitoring during anaesthesia. Inevitably much of the research is first done in adults and later in children. This review will focus on the recent paediatric publications (2017-2019) in two areas of neuromonitoring - measuring anaesthesia effect and cerebral perfusion and oxygenation.

RECENT FINDINGS

For EEG-derived depth monitors, the main recent advances have been in better understanding their performance in infants. For the first time, large multichannel EEG studies on infants have focused on understanding the basic principles of how anaesthesia impacts on the EEG of the developing brain in a way different to the older brain. Nociception monitors are beginning to be studied in children. In the area of optical neuromonitoring, studies show that cerebral desaturation during both general and spinal anaesthesia in infants is uncommon in neonates and infants. Further work emphasizes the importance of CO2 levels on cerebral oxygenation, and demonstrates impaired cerebral autoregulation in premature infants undergoing laparotomies.

SUMMARY

The impact of anaesthesia on the EEG of small infants has some gross similarities to older children but there are fundamental differences, which mandate separate calibration of anaesthesia depth monitors. The role of nociception monitors in children has yet to be defined. Cerebral oxygenation monitoring during paediatric anaesthesia is improving our understanding of cerebral perfusion in this period, but as with almost all monitoring, evidence that its use improves outcome is not yet available.