Clinical signs and electroencephalographic patterns of emergence from sevoflurane anaesthesia in children

Abstract

BACKGROUNDFew studies have systematically described relationships between clinical–behavioural signs, electroencephalographic (EEG) patterns and age during emergence from anaesthesia in young children.OBJECTIVETo identify the relationships between end-tidal sevoflurane (ETsevoflurane) concentration, age and frontal EEG spectral properties in predicting recovery of clinical–behavioural signs during emergence from sevoflurane in children 0 to 3 years of age, with and without exposure to nitrous oxide. The hypothesis was that clinical signs occur sequentially during emergence, and that for infants aged more than 3 months, changes in alpha EEG power are correlated with clinical–behavioural signs.DESIGNAn observational study.SETTINGA tertiary paediatric teaching hospital from December 2012 to August 2016.PATIENTSNinety-five children aged 0 to 3 years who required surgery below the neck.OUTCOME MEASURESTime–course of, and ETsevoflurane concentrations at first gross body movement, first cough, first grimace, dysconjugate eye gaze, frontal (F7/F8) alpha EEG power (8 to 12 Hz), frontal beta EEG power (13 to 30 Hz), surgery-end.RESULTSClinical signs of emergence followed an orderly sequence of events across all ages. Clinical signs occurred over a narrow ETsevoflurane, independent of age [movement: 0.4% (95% confidence interval (CI), 0.3 to 0.4), cough 0.3% (95% CI, 0.3 to 0.4), grimace 0.2% (95% CI, 0 to 0.3); P > 0.5 for age vs. ETsevoflurane]. Dysconjugate eye gaze was observed between ETsevoflurane 1 to 0%. In children more than 3 months old, frontal alpha EEG oscillations were present at ETsevoflurane 2.0% and disappeared at 0.5%. Movement occurred within 5 min of alpha oscillation disappearance in 99% of patients. Nitrous oxide had no effect on the time course or ETsevoflurane at which children showed body movement, grimace or cough.CONCLUSIONSeveral clinical signs occur sequentially during emergence, and are independent of exposure to nitrous oxide. Eye position is poorly correlated with other clinical signs or ETsevoflurane. EEG spectral characteristics may aid prediction of clinical–behavioural signs in children more than 3 months.

Case Studies Using the Electroencephalogram to Monitor Anesthesia-Induced Brain States in Children

“…From minutes 204 to 208 and before patient movement, there is a noticeable shift seen on the EEG: beta oscillations begin to shift upward in frequency and become weaker, while power within the 7–15 Hz range disappears. These changes appear consistent with the previously discussed “unzipping” pattern of emergence from anesthesia in adults (Figure 3 ) 3 , 4 and in children 57 and suggest that the patient entered a “lighter” anesthetic state during this time. Given that the patient began to move as this state progressed, the spectrogram pattern between minutes 204 and 208 likely represents the infant equivalent of emergence seen in older patients.…”

“…Figure 5 D shows an example of this effect in the spectrogram from an 8-month-old patient emerging from sevoflurane in N 2 O/O 2 , showing the same “unzipping” pattern. 57 In the present case, after the propofol bolus, there is a significant increase in slow power (minutes 209–212), which is a characteristic change seen in adults representing a deeper state of unconsciousness. 4 The following 6 minutes of EEG recording shows a spectrogram that is blue at nearly all frequencies above approximately 1 Hz, indicating that the EEG signal has significantly diminished in size.…”

Neural Correlates of Anesthesia in Newborn Mice and Humans

“…The most commonly used of such methods, the Bispectral Index, has been shown to significantly reduce intraoperative awareness, amount of anesthetic used, recovery time and post-anesthesia care unit stay in a recent Cochrane meta-analysis (Punjasawadwong et al, 2014), but see (Kalkman et al, 2011; Hajat et al, 2017). However, evidence of similar benefits in infants and younger children is sparse, as recently shown (Cornelissen et al, 2015, 2017, 2018a). EEG in anesthetized infants changes dramatically depending on postnatal age.…”

“…However, in preterm and term neonates for the first weeks of life, EEG during sleep-wake cycles is weakly correlated with behavioral states and shows characteristic bursts or spontaneous activity transients (Milh et al, 2007; O’Toole et al, 2016). Anesthesia-induced theta and alpha oscillations have been reported to emerge around 3–4 months of age, albeit with less frontal predominance than in older children and adults (Cornelissen et al, 2015, 2018a). Moreover, high concentrations/doses of anesthetics have been reported to depress brain activity and enhance signal discontinuity in both human and rodent neonates (Chang et al, 2016; Cornelissen et al, 2017; Stolwijk et al, 2017).…”

Identifying neurophysiological features associated with anesthetic state in newborn mice and humans

“…In adult human volunteers, the correlation with anesthetic depth and EEG parameters can be performed using verbal reports to establish a threshold for unconsciousness ( 15 ). However, in non-verbal populations such as human infants, one must rely on indirect behavioral measures which are more readily performed on emergence rather than induction and incision ( 54 ). Future investigations need to include surgical incision and other stimuli into the mouse models to understand with greater granularity the anesthetic titration around the minimal concentrations required to suppress movement, autonomic, and cortical responses to noxious stimuli.…”