Characterisation of awakening from anaesthesia in infants.
Doctoral thesis, UCL (University College London).
There is uncertainty about the doses of anaesthetic drugs required for unconsciousness in infants. It is important to both avoid inadequate doses leading to intraoperative awareness and also excess doses that may harm the developing brain. Depth of anaesthesia monitoring has been developed in adults based upon electroencephalography (EEG). The EEG of infants is different and few data are available. Heart rate variability (HRV) using the ECG is another non-invasive tool that could be used in infants. The hypothesis of this thesis is that EEG and HRV could help predict or warn of awakening after anaesthesia. Awakening was defined by a panel of experts as at least 2 of crying, coughing, vigorous limb movements, eyes open or looking around. A suitable clinical model of awakening from anaesthesia was determined in a series of pilot studies. Intubated infants anaesthetised with sevoflurane were studied after surgery. Tickling the foot proved a reliable stimulus to cause awakening. EEG and HRV were monitored at the end of surgery during emergence. Events and behaviour were videoed and characteristics of EEG and HRV were identified. After awakening began EMG and other interference made signals difficult to interpret. In all infants there was negligible EEG power in frequencies higher than 20Hz and most power was in frequencies less than 5Hz. Infants older than 52 weeks post menstrual age (PMA) had an oscillatory characteristic within the 5 to 20 Hz range during anaesthesia that reduced in power appreciably as sevoflurane levels decreased; power in 5-20 Hz reduced to less than 100 μV2 before awakening began which may provide a potential warning of awakening. Infants less than 52 weeks PMA had low EEG power in 5-20 Hz throughout. EEG power in this frequency band during anaesthesia increases with age. HRV was low during anaesthesia but increased before awakening began. HRV low frequency power increased in bursts as anaesthesia levels decreased. A case report demonstrated the potential value of P5-20Hz and LF HRV band power in the development of intraoperative depth of anaesthesia monitoring in infants older than 52 weeks PMA.
|Title:||Characterisation of awakening from anaesthesia in infants|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Child Health > Department of Cardiorespiratory Sciences > ICH - Portex Anaesthesia|
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