Correlation of exhaled propofol with Narcotrend index and calculated propofol plasma levels in children undergoing surgery under total intravenous anesthesia - an observational study

Abstract

Background Exhaled propofol concentrations correlate with propofol concentrations in adult human blood and the brain tissue of rats, as well as with electroencephalography (EEG) based indices of anesthetic depth. The pharmacokinetics of propofol are however different in children compared to adults. The value of exhaled propofol measurements in pediatric anesthesia has not yet been investigated. Breathing system filters and breathing circuits can also interfere with the measurements. In this study, we investigated correlations between exhaled propofol (exP) concentrations and the Narkotrend Index (NI) as well as calculated propofol plasma concentrations. Methods A multi-capillary-column (MCC) combined with ion mobility spectrometry (IMS) was used to determine exP. Optimal positioning of breathing system filters (near-patient or patient-distant) and sample line (proximal or distal to filter) were investigated. Measurements were taken during induction (I), maintenance (M) and emergence (E) of children under total intravenous anesthesia (TIVA). Correlations between ExP concentrations and NI and predicted plasma propofol concentrations (using pediatric pharmacokinetic models Kataria and Paedfusor) were assessed using Pearson correlation and regression analysis. Results Near-patient positioning of breathing system filters led to continuously rising exP values when exP was measured proximal to the filters, and lower concentrations when exP was measured distal to the filters. The breathing system filters were therefore subsequently attached between the breathing system tubes and the inspiratory and expiratory limbs of the anesthetic machine. ExP concentrations significantly correlated with NI and propofol concentrations predicted by pharmacokinetic models during induction and maintenance of anesthesia. During emergence, exP significantly correlated with predicted propofol concentrations, but not with NI. Conclusion In this study, we demonstrated that exP correlates with calculated propofol concentrations and NI during induction and maintenance in pediatric patients. However, the correlations are highly variable and there are substantial obstacles: Without patient proximal placement of filters, the breathing circuit tubing must be changed after each patient, and furthermore, during ventilation, a considerable additional loss of heat and moisture can occur. Adhesion of propofol to plastic parts (endotracheal tube, breathing circle) may especially be problematic during emergence. Trial Registration The study was registered in the German registry of clinical studies (DRKS-ID: DRKS00015795).

Exhaled breath is found to be better than blood samples for determining propofol concentrations in the brain tissues of rats

“…But the correlations were not good in all studies. In pediatric patients, Heiderich et al used MCC-IMS to demonstrate moderate correlations between exhaled propofol concentration and the Narcotrend Index [30]. The study of Braathen et al found that the modest correlation whether in normal-weight or obese surgical patients makes the bedside online IMS device's everyday clinical usefulness questionable [31].…”

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

“…The NI was originally developed as an EEG-based monitoring modality for general anesthesia and correlates with the minimal alveolar concentration of sevoflurane and exhaled propofol during anesthesia [ 18 , 19 , 20 ]. During transition from induction to maintenance, the use of NI can help to reduce the use of intraoperative propofol [ 21 ] and guide sedation depth during endoscopies under an opiate and propofol [ 22 , 23 ].…”

Meta-Analysis of the Prognostic Value of Narcotrend Monitoring of Different Depths of Anesthesia and Different Bispectral Index (BIS) Values for Cognitive Dysfunction after Tumor Surgery in Elderly Patients

“…Studies have shown that maintaining an intraoperative bispectral index (BIS) value of 30-40 is more conducive to the recovery of early postoperative cognitive function. In this study, a metaanalysis was conducted to systematically evaluate the impact of different BIS values on POCD in order to provide a clinical reference [3].…”