Pethidine effect on the neonatal EEG

217 A method of on-line computerized neonatal EEG monitoring and analysis, D. Wertheim, D. MurdochEaton, R. Oozeer, J. Connell, R. Willetts, L. Dubowitz, V. Dubowitz and R. Wootton. Department of Paediatrics and Neonatal Medicine and Department of Medical Physics, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 OHS, U.K. We have previously reported a computerized method of analysis of neonatal electroencephalographic (EEG) recordings made on the Oxford 4-24 Medilog recorder [ 11. The system has now been further developed to enable us to analyse and display the EEG on-line. The Medilog recorder is connected via isolation amplifiers and filters to an analogue-to-digital converter in a portable computer. The system analyses two channels of EEG for continuity and amplitude and stores data on hard disk for further examination. In addition the EEG waveform is continuously displayed and a printout of the interval duration in 1 min epochs for both recording sites is available which gives an indication of the discontinuity of the EEG. The on-line system has been used to analyse recordings on 20 premature babies. Changes in EEG continuity have been observed on-line during drug administration. We have also seen increasing discontinuity associated with respiratory acidosis which when corrected by alteration of ventilation settings was associated with a decrease in discontinuity. To evaluate these observations further we are adding simultaneous on-line monitoring and analysis of other physiological measurements. 1

Wertheim, D., Connell, J., Brydon, J., Oozeer, R. and Dubowitz, V. (1988): Early Human Dev., 18.227.

Petbidine effect on the neonatal EEG, D. Murdoch-Eaton, D. Wertheim, R. Oozeer, L. Dubowitz and V. Dubowitz. Royal Postgraduate Medical School, Hammersmith Hospital, Du Cane Road, London W12, U.K. Continuous recordings of the EEG of ventilated premature infants were obtained using Oxford medilog 4-24 channel recorders with “on-line” computer analysis [l]. This method allows accurate timing and effects of drug administration to be studied. Sixteen infants were sequentially monitored, the only criteria for entry being that they were ventilated and therefore most likely to receive pethidine as a sedative to aid mechanical ventilation. Twelve of these received pethidine at a standard dose of 1 mg/kg at intervals determined by the clinical state of the infant. Gestations ranged from 26 to 31 weeks (median 28.5 weeks), weight from 0.87 to 1.66 kg (median 1.11 kg). Recording was commenced as soon as possible after birth - median time 5.2 h (range 3.3-l 1.9 h). Reactions to the dose of pethidine were characterised by a marked increase in discontinuity of the EEG, and on some occasions also a decrease in variability. Termination of the effect was noted by a return to pre-dose levels of variability and continuity of the EEG. Nine babies were monitored during the administration of their first dose of pethidine and all showed a marked reaction with a median duration of reaction of 2.0 h (range 0.9-3.6 h). At the time of the second dose 11 of the 12 monitored showed reactions (91.7QIo),with a median duration of reaction of 0.45 h (range 0.2-3.5 h). After the fourth dose at a median age of 21.5 h (range 15.5-46.2 h) there were reactions in 6 of the 9 monitored, with a median duration of reaction of 1.15 h (range 0.2-2.1). There appeared to be a shortening of duration of effect of doses given over the first 24 h, but the relationship after this time is less clear. By the 10th dose given at a median age of 50.5 h (range 40.5-59.7 h) reactions were only seen in 2 of the 7 monitored. None of these infants developed significant cerebral pathology and there were no obvious associated changes in any of the physiological parameters measured during these reactions. Both the mechanism and significance of the EEG changes remain unexplained. 1

Wertheim, D., Connell, J., Oozeer, R., Brydon, J., Dubowitz, L.M.S. and Dubowitz, V. (1988): EarlyHumanDev., 18,227.