Clinical signs and electroencephalographic patterns of emergence from sevoflurane anaesthesia in children: An observational study

Abstract

Background: Few studies have systematically described relationships between clinical-behavioural signs, electroencephalographic (EEG) patterns and age during emergence from anaesthesia in young children.

Objective: To 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.

Design: An observational study.

Setting: A tertiary paediatric teaching hospital from December 2012 to August 2016.

Patients: Ninety-five children aged 0 to 3 years who required surgery below the neck.

Outcome measures: Time-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.

Results: Clinical 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.

Conclusion: Several 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.

Figures

Fig. 1

Study profile.

Fig. 2

Clinical–behavioural signs of emergence from sevoflurane general anaesthesia. (a) Group-average median time since procedure end, or (b) group average median end-tidal sevoflurane when first body movement, cough or grimace were observed. Within-patient time from surgical procedure end and within patient End-tidal sevoflurane concentration for children who exhibited all clinical–behavioural signs during emergence from sevoflurane in air/oxygen (c and d) or from sevoflurane in nitrous oxide in oxygen (e and f). Negative times indicate the event occurred before the end of surgery as a result of the anaesthetist reducing sevoflurane concentrations in preparation for the end of surgery.∗∗P < 0.01; ∗∗∗P < 0.001. Cg, first cough; ETsevoflurane, end-tidal sevoflurane concentration; Gr, first grimace; Move, first body movement; N2O/O2, nitrous in oxygen; O2, oxygen.

Fig. 3

Relationship with clinical signs, end-tidal sevoflurane concentration and age in children during emergence from sevoflurane general anaesthesia. Individual end-tidal sevoflurane when first body movement, cough or grimace were observed for patients who emerged from sevoflurane in air/oxygen (a to c) or in nitrous in oxygen (d to f). Top panel illustrates first gross body movement; middle panel illustrates first cough; bottom panel illustrates first grimace. Data points represent individual patients. Solid line represents linear regression; shaded area represents 95% confidence interval. ETsevoflurane, end-tidal sevoflurane concentration; M, months; n, number; N2O/O2, nitrous in oxygen; O2, oxygen.

Fig. 4

Relationship with eye gaze and end-tidal sevoflurane concentration during emergence from sevoflurane general anaesthesia. Dysconjugate eye gaze was observed between end-tidal sevoflurane 1 to 0%, and was poorly correlated with appearance of clinical signs. The percentage of patients with dysconjugate eye gaze at each end-tidal sevoflurane decrement in children who emerged from (a) sevoflurane in air/oxygen (n = 31) and (b) from sevoflurane in nitrous in oxygen (n = 16). ETsevoflurane, end-tidal sevoflurane concentration. Individual eye gaze assessment results are given in Supplementary Digital Content 2.

Fig. 5

Time–frequency frontal electroencephalographic properties during emergence from sevoflurane general anaesthesia. Individual frontal electroencephalographic spectrograms computed at F7, clinical–behavioural signs and end-tidal sevoflurane in two infants aged 8 months old. (a to c) Infant 1 with sevoflurane in air/oxygen and (d to f) Infant 2 with sevoflurane in nitrous in oxygen. Top panel (a and d) illustrates individual frontal spectrograms; middle panel (b and e) illustrates presence of alpha oscillations, first body movement, first cough or first grimace (in which ‘1’ indicates response, ‘0’, no response) and eye gaze position (in which vertical line indicates when an eye gaze assessment was made); and bottom panel (c and f) illustrates end-tidal sevoflurane and ETN2O over time. Conj, conjugate eye gaze; Dys, dysconjugate eye gaze; ETsevoflurane, end-tidal sevoflurane concentration; ETN2O, end-tidal nitrous oxide concentrations; N2O, nitrous oxide; O2, oxygen.

Fig. 6

Summary of clinical behavioural signs, electroencephalographic power and end-tidal sevoflurane concentration during emergence in children. (a) Percentage of children who exhibited recovery of body movement, cough, grimace and alpha oscillation disappearance and the associated end-tidal sevoflurane. (b) Receiver operating curve model to estimate sensitivity and specificity of end-tidal sevoflurane, frontal alpha electroencephalographic power and frontal electroencephalographic beta power in predicting the occurrence of body movement. Data shown for children more than 3 months of age with and without nitrous oxide exposure. ETsevoflurane, end-tidal sevoflurane concentration.