Prognostic significance of amplitude-integrated EEG during the first 72 hours after birth in severely asphyxiated neonates

Neurodevelopmental outcome in term infants with status epilepticus detected with amplitude-integrated electroencephalography

OBJECTIVES

This study evaluated seizure, patient characteristics, and neurodevelopmental outcome of term newborns with amplitude-integrated electroencephalography-detected status epilepticus.

METHODS

Fifty-six term infants with status epilepticus were identified during a 12.5-year period. The time of onset of status epilepticus, background pattern before and after status epilepticus, success of controlling status epilepticus with antiepileptic drugs, and neurodevelopmental outcome were studied.

RESULTS

The incidence of status epilepticus in our population was 18%. Forty-two infants (75%) had a poor outcome and 14 were normal at follow-up. When all infants were studied as a single group, we found that not the duration, but the background pattern was correlated with neurodevelopmental outcome. In 50% of the infants with a poor outcome, the background pattern was abnormal before the status epilepticus and in 71% after the status epilepticus. Among infants with a good outcome, background pattern was normal in 14% before and 7% after the status epilepticus. In a subgroup of 48 infants with hypoxic-ischemic encephalopathy, there was a significant difference in background pattern, as well as in duration of the status epilepticus between infants with a poor outcome, compared with those with a good outcome. In 48% of the infants with a poor outcome, the background pattern was abnormal before, and in 75% after the status epilepticus, compared with 25% and 13%, respectively, for those with a good outcome. In 57% of the infants with a hemorrhage or perinatal arterial stroke, the status epilepticus was not controlled with antiepileptic drugs, compared with 21% in infants with hypoxic-ischemic encephalopathy (not significant).

CONCLUSIONS

The background pattern at the onset of status epilepticus was the main predictor of neurodevelopmental outcome. The duration of the status epilepticus was only of predictive value in the infants with hypoxic-ischemic encephalopathy. No association was found between the ability to control status epilepticus and subsequent neurodevelopmental outcome.

Monitoring the neonatal brain: a survey of current practice among Australian and New Zealand neonatologists

AIMS

There is considerable variation in the use of brain imaging and electrophysiological monitoring of encephalopathic term infants. The aims of this study were (i) to document the current practice among Australian and New Zealand neonatologists; and (ii) to identify the factors that influence local practice.

METHODS

A postal questionnaire was sent to all 152 neonatologists in Australia and New Zealand. A hypothetical scenario of an encephalopathic term infant was presented and clinicians were asked a series of questions relating to their use of magnetic resonance imaging (MRI), computed tomography, ultrasound, electroencephalography and amplitude integrated electroencephalography.

RESULTS

There was a 62% response rate. Twenty-two per cent of respondents would not routinely perform an MRI brain scan in the given scenario. Limited availability, expense, logistics of transport and a lack of confidence in the ability of MRI to provide additional clinical information appear to be the main factors affecting practice. When a scan is performed, the majority of respondents (72%) perform the scan on day 5 or later. Twenty-three per cent of respondents experience significant delays when they request an MRI scan. Regarding electrophysiological monitoring, amplitude integrated electroencephalography would be used by 62% of respondents in the given scenario.

CONCLUSIONS

This study demonstrates that MRI is now widely used by neonatologists in Australia and New Zealand. However, local resource limitations and a lack of confidence in the utility of MRI continue to limit its use.

The added value of simultaneous EEG and amplitude-integrated EEG recordings in three newborn infants

Amplitude-integrated electroencephalograms (aEEGs) recorded by cerebral function monitors (CFMs) are used increasingly to monitor the cerebral activity of newborn infants with encephalopathy. Recently, new CFM devices became available which also reveal the original EEG signals from the same leads. To date it was unclear whether this single-lead EEG provides additional information towards interpreting the aEEG traces more accurately. Our report deals with three cases in which the single-lead EEG from the CFM device did indeed reveal important additional information not provided by the aEEG alone. In cases 1 and 3, the aEEGs showed drifting of the baseline to higher amplitudes. The single-lead EEG revealed that this was due to muscle artefacts, high-frequency oscillation ventilation and the electrocardiogram rather than to cerebral activity. Hence, without knowledge of the EEG, the aEEG trace might have been misinterpreted as being fairly normal. Case 2 showed paroxysmal elevation of the lower margin of the amplitude on the aEEG which looked like epileptic activity. However, additional information from the single-lead EEG revealed that it was due to muscle artefacts. Thus, simultaneously recorded EEG can help to interpret seizure-like episodes on the aEEG.

CONCLUSION

Simultaneously recorded single-lead EEGs can help to interpret aEEG traces more accurately.

Continuous brain-function monitoring: state of the art in clinical practice

Continuous electroencephalographic (EEG) monitoring gives direct information on brain function in newborn infants needing intensive care. To improve the possibilities of long-term monitoring, the EEG is time-compressed and recorded with a reduced number of electrodes. A trend measure of the EEG, the amplitude-integrated EEG (aEEG), has proved capable of giving relevant information in newborn infants of differing levels of maturity. The electrocortical background activity gives information on the level of brain activity, which is associated with outcome in both term asphyxiated infants and in preterm infants. However, the background activity is also affected by several medications, and this must be considered when interpreting the aEEG trace. The aEEG also reveals subclinical epileptic seizure activity, and can be used for evaluation of anti-epileptic treatment. The aEEG should be used as a complement to the standard EEG, and close collaboration between neonatologists and clinical neurophysiologists is necessary for optimal performance of EEG monitoring.

Amplitude integrated electroencephalography in the full-term newborn

Amplitude-integrated electroencephalography (aEEG) is beginning to play an important role in the care of full-term infants who have neonatal encephalopathy. The three main features an aEEG provides include (1) the background pattern, showing the activity at admission to the neonatal intensive care unit and the rate of recovery during the first 24 to 48 hours after birth; (2) the presence or absence of sleep-wake cycling; and (3) the presence of most electrographic discharges.

The physiological basis for continuous electroencephalogram monitoring in the neonate

Continuous monitoring of the electrocortical activity as compared with intermittent recording sessions offers a possibility of revealing changes of the condition of the brain, relevant for clinical decisions. Furthermore, trend monitoring, such as amplitude integrated electroencephalogram (aEEG), helps the clinician in extracting features such as background activity, sleep-waking cycling, and seizure patterns, which have been proven relevant for prognosis and treatment of the preterm and sick term infant. A coherent model for classification and description of neonatal aEEG patterns is presented.

Use of 2-channel bedside electroencephalogram monitoring in term-born encephalopathic infants related to cerebral injury defined by magnetic resonance imaging

OBJECTIVE

Single-channel amplitude-integrated electroencephalography has been shown to be predictive of neurodevelopmental outcome in term infants with hypoxic-ischemic encephalopathy. We describe the relationship of quantifiable electroencephalogram (EEG) measures, obtained using a 2-channel digital bedside EEG monitor from term newborn infants with encephalopathy and/or seizures, to cerebral injury defined qualitatively by MRI.

METHODS

Median values of minimum, mean, and maximum EEG amplitude were obtained from term-born encephalopathic infants during a 2-hour seizure-free period obtained within 72 hours of admission. Infants underwent MRI with images qualitatively scored for abnormalities of cortex, white matter, deep nuclear gray matter, and posterior limb of the internal capsule. Eighty-six infants had EEG measures related to qualitative MRI outcomes.

RESULTS

The most common diagnosis was hypoxic ischemic encephalopathy (n = 40). For all infants there was a negative relationship between EEG amplitude measures and MRI abnormality scores assessed on a scale from 4 to 15, with a higher score indicating more abnormalities. This relationship was strongest for the minimum amplitude measures in both hemispheres; that is, for every unit increase in score there was a mean drop of 0.41 microV for the left cerebral hemisphere, with 35% of variance explained. This relationship persisted on sub-group analyses for infants with hypoxic-ischemic encephalopathy, infants with other diagnoses and infants monitored after the first 24 hours of life. Using an MRI abnormality score cutoff of 8 or worse for cerebral injury in infants with hypoxic-ischemic encephalopathy, a minimum amplitude of 4 microV showed a higher specificity (80%: left hemisphere), whereas a minimum amplitude of 6 muV showed a higher sensitivity (92%: left hemisphere).

CONCLUSIONS

Bedside EEG measures in term-born encephalopathic infants are related to the severity of cerebral injury as defined by qualitative MRI. A minimum amplitude of <4 microV appears useful in predicting outcome.

Cerebral oxygenation and electrical activity after birth asphyxia: their relation to outcome

OBJECTIVE

To determine the value of regional cerebral oxygen saturation (rSo2), fractional cerebral tissue oxygen extraction (FTOE) measured by near-infrared spectroscopy (NIRS), and amplitude integrated electroencephalogram (aEEG) after birth asphyxia in relation to neurodevelopmental outcome.

METHODS

NIRS measured rSo2, FTOE, and aEEG were monitored simultaneously, together with arterial oxygen saturation (Sao2) and blood pressure during the first 48 hours after severe birth asphyxia in 18 term infants. FTOE was calculated as [Sao2-rSo2]/Sao2. Neurodevelopmental outcome was assessed at 3, 9, and 18 months and 3 and 5 years of age. At the time points 6, 12, 18, 24, 30, 36, 42, and 48 hours after birth, the mean values of Sao2, rSo2, FTOE, and mean arterial blood pressure were calculated over a 1-hour period. A stepwise-regression model was used to investigate the relative contribution of rSo2, FTOE, or aEEG to developmental outcome.

RESULTS

Nine Infants died during the neonatal period as a result of neurologic deterioration, and 8 infants had a normal outcome at 5 years of age. One child developed learning disabilities and a mild diplegia. The rSo2 and FTOE remained stable in infants with a normal outcome. The rSo2 increased and the FTOE decreased after 24 hours in the infants with an adverse outcome. (rSo2: 65% vs 84% at 12 and 48 hours, respectively; FTOE: 0.32 vs 0.12 at 12 and 48 hours, respectively). aEEG showed the closest relationship with outcome, but also rSo2 showed a significant correlation 24 hours after birth.

CONCLUSIONS

rSo2 and FTOE seem to reflect secondary energy failure. aEEG showed the closest relationship with outcome after severe birth asphyxia.

Mild hypothermia and the distribution of cerebral lesions in neonates with hypoxic-ischemic encephalopathy

Hypothermia induced by whole-body cooling (WBC) and selective head cooling (SHC) both reduce brain injury after hypoxia-ischemia in newborn animals, but it is not known how these treatments affect the incidence or pattern of brain injury in human newborns. To assess this, 14 term infants with hypoxic-ischemic encephalopathy (HIE) treated with SHC, 20 infants with HIE treated with WBC, and 52 noncooled infants with HIE of similar severity were studied with magnetic resonance imaging in the neonatal period. Infants fulfilling strict criteria for HIE were recruited into the study after assessment of an amplitude-integrated electroencephalography (aEEG). Cooling was commenced within 6 hours of birth and continued for 48 to 72 hours. Hypothermia was not associated with unexpected or unusual lesions, and the prevalence of intracranial hemorrhage was similar in all 3 groups. Both modes of hypothermia were associated with a decrease in basal ganglia and thalamic lesions, which are predictive of abnormal outcome. This decrease was significant in infants with a moderate aEEG finding but not in those with a severe aEEG finding. A decrease in the incidence of severe cortical lesions was seen in the infants treated with SHC.

Role of cerebral function monitoring in the newborn

For many years, newborn infants admitted to neonatal intensive care units have had routine electrocardiography and been monitored for respiratory rate, heart rate, oxygen saturation, and blood pressure. Only recently has it also been considered important to monitor brain function using continuous electroencephalography. The role of cerebral function monitoring in sick full term and preterm infants is reviewed.

Recovery of amplitude integrated electroencephalographic background patterns within 24 hours of perinatal asphyxia

OBJECTIVE

To assess the time course of recovery of severely abnormal initial amplitude integrated electroencephalographic (aEEG) patterns (flat trace (FT), continuous low voltage (CLV), or burst suppression (BS)) in full term asphyxiated neonates, in relation to other neurophysiological and neuroimaging findings and neurodevelopmental outcome.

METHODS

A total of 190 aEEGs of full term infants were reviewed. The neonates were admitted within 6 hours of birth to the neonatal intensive care unit because of perinatal asphyxia, and aEEG recording was started immediately. In all, 160 infants were included; 65 of these had an initial FT or CLV pattern and 25 an initial BS pattern. Neurodevelopmental outcome was assessed using a full neurological examination and the Griffiths' mental developmental scale.

RESULTS

In the FT/CLV group, the background pattern recovered to continuous normal voltage within 24 hours in six of the 65 infants (9%). All six infants survived the neonatal period; one had a severe disability, and five were normal at follow up. In the BS group, the background pattern improved to normal voltage in 12 of the 25 infants (48%) within 24 hours. Of these infants, one died, five survived with moderate to severe disability, two with mild disability, and four were normal. The patients who did not recover within 24 hours either died in the neonatal period or survived with a severe disability.

CONCLUSION

In this study there was a small group of infants who presented with a severely abnormal aEEG background pattern within six hours of birth, but who achieved recovery to a continuous normal background pattern within the first 24 hours. Sixty one percent of these infants survived without, or with a mild, disability.

Sleep-wake cycling on amplitude-integrated electroencephalography in term newborns with hypoxic-ischemic encephalopathy

OBJECTIVE

The objective of this amplitude-integrated electroencephalography (aEEG) study was to evaluate the influence of perinatal hypoxia-ischemia on sleep-wake cycling (SWC) in term newborns and assess whether characteristics of SWC are of predictive value for neurodevelopmental outcome.

METHODS

From a consecutive series of newborns born during a 10-year period, the aEEG tracings of 171 term newborns with hypoxic-ischemic encephalopathy were assessed for the presence, time of onset, and quality of SWC. SWC patterns were categorized with regard to the background pattern on which they presented, as normal or abnormal SWC.

RESULTS

SWC was seen in 95.4% of the surviving newborns and in 8.1% of those who died. The median time intervals from birth to onset of SWC were significantly different in newborns with hypoxic-ischemic encephalopathy grades I, II, and III (7, 33, and 62 hours, respectively). Newborns with seizure discharges developed SWC with a delay of 30.5 hours. Good outcome was associated with earlier onset of SWC and normal SWC pattern. The difference in the median Griffiths' developmental quotients in newborns who started SWC before/after 36 hours was 8.5 points. The good/poor neurodevelopmental outcome was predicted correctly by the onset of SWC before/after 36 hours in 82% of newborns.

CONCLUSIONS

The presence, time of onset, and quality of SWC reflected the severity of the hypoxic-ischemic insult to which newborns were exposed. The time of onset of SWC has a predictive value for neurodevelopmental outcome.