No abstract

There is uncertainty about the level of systemic blood pressure required to maintain adequate cerebral oxygen delivery and organ integrity. This prospective, observational study on 35 very low birth weight infants aimed to determine the mean blood pressure (MBP) below which cerebral electrical activity, peripheral blood flow (PBF), and cerebral fractional oxygen extraction (CFOE) are abnormal. Digital EEG, recorded every day on the first 4 d after birth, were analyzed a) by automatic spectral analysis, b) by manual measurement of interburst interval, and c) qualitatively. CFOE and PBF measurements were performed using near-infrared spectroscopy and venous occlusion. MBP was measured using arterial catheters. The median (range) of MBP recorded was 32 mm . The EEG became abnormal at MBP levels below 23 mm Hg: a) the relative power of the delta (0.5-3.5 Hz) frequency band was decreased, b) interburst intervals were prolonged, and c) all four qualitatively abnormal EEG (low amplitude and prolonged interburst intervals) from four different patients were recorded below this MBP level. The only abnormally high CFOE was measured at MBP of 20 mm Hg. PBF decreased at MBP levels between 23 and 33 mm Hg. None of the infants in this study developed cystic periventricular leukomalacia. One infant (MBP, 22 mm Hg) developed ventricular dilatation after intraventricular hemorrhage. The EEG and CFOE remained normal at MBP levels above 23 mm Hg. It would appear that cerebral perfusion is probably maintained at MBP levels above 23 mm Hg. (Pediatr Res 59: 314-319, 2006) S everal authors have described an association between systemic hypotension in premature infants and neurologic morbidity (1-3), and, in some centers, clinical practice is to support blood pressure by inotropes and volume expanders when the MBP level falls below 30 mm Hg. The likely mechanism by which hypotension causes neurologic damage is by diminished oxygen delivery through decreased cerebral perfusion. However, the relationship between MBP and cerebral blood flow is unclear in premature infants (4 -8). Some authors have argued that cerebral blood flow is pressure passive and dependent on MBP in infants between 28 and 39 wk gestation (5,7). Others, who have studied infants between 24 and 34 wk gestation, observed that cerebral blood flow is independent of MBP (4,8). Furthermore, the critical level of MBP at which cerebral perfusion becomes compromised has not been clearly determined.In spite of a lack of evidence linking systemic hypotension to brain damage in very low birth weight infants, it is well known that older subjects lose consciousness when MBP falls to a seriously low level. A change in the level of consciousness may not be recognized in sick newborn infants who are heavily sedated while being ventilated, but it may be associated with recognizable changes in the EEG pattern. Using a cerebral function monitor, Greisen et al. (9) showed that reduced blood flow to the neonatal brain correlated with decreased amplitude of the EEG. There have bee...

Continuous EEG monitoring has not been used widely in neonatal intensive care, especially in the care of extremely premature infants, probably in part because of a lack of a reliable quantitative method. The purpose of this study was to quantify the EEG of the very premature infants just after birth by using spectral analysis and to describe the characteristics of the spectral signal when infants were clinically stable. Digital EEG recordings were performed on 53 infants who were Յ30 wk gestation for 75 min each day during the first 4 d after birth. Artefact was rejected manually after visual inspection of trace. The EEG was analyzed by manual measurement of interburst interval and automatically by spectral analysis using Fast Fourier Transformation. Spectral analysis generated the normal ranges of the relative power of the ␦ (0.5-3.5 Hz), (4 -7.5 Hz), ␣ (8 -12.5 Hz), and ␤ (13-30 Hz) frequency bands, spectral edge frequency, and symmetry. The median (range) relative power of the ␦ band increased significantly from 68% (62-76%) on day 1 to 81% (72-89%) on day 4 (p ϭ 0.001). The interburst intervals became progressively shorter between days 1 [14s (10 -25)] and 3 [8s (6 -12)]; there were no significant differences between days 3 and 4. The relative power of the ␦ band seemed to be the most useful and repeatable spectral measurement for continuous long-term monitoring. However, automatic artefact rejection software needs to be developed before continuous quantitative EEG monitoring can be used in the neonatal intensive care environment. The hemodynamic status of extremely premature infants is particularly labile during the first days after birth. Intensive interventions for such infants are intended to maintain an adequate tissue oxygen supply, particularly to the brain. Because clinical management is aimed at preserving cerebral integrity in these infants, it would be helpful to have some form of continuous neuromonitoring to guide clinical interventions. EEG provides a useful, noninvasive technique for monitoring cerebral electrical activity, and advances in digital technology have made it possible to record high-quality EEG even in an electrically noisy intensive care environment and have done away with the necessity of using large amounts of recording paper. However, interpretation of the EEG is generally considered to be highly specialized, and this is at least one reason that continuous EEG monitoring is not used widely in neonatal intensive care.There are three major issues to be considered for the automatic and reliable analysis of the EEG signal of premature infants and for data to be presented in a manner that is useful to clinicians. First, the EEG of these infants consists predominantly of high-amplitude slow waves (1,2). Bell et al. (3) showed that the relative power of slow waves with frequency Ͻ1 Hz might be as high as 90% in infants at 28 wk gestation. A recent study using DC EEG on infants between 34 and 37 wk gestation found that the spontaneous EEG activity of sleeping preterm infants consiste...

Photosensitivity is reported to occur in approximately 40% of patients with juvenile myoclonic epilepsy. Our experience suggests that the prevalence is higher and may be related to both the duration of intermittent photic stimulation and also the age at which the procedure is undertaken. A two-year retrospective review of all EEGs was undertaken on all children attending a paediatric EEG department to identify those with juvenile myoclonic epilepsy. Photosensitivity was defined as a generalized spike or spike-wave paroxysm occurring at least twice during intermittent photic stimulation. Sixty-one children with a diagnosis of juvenile myoclonic epilepsy with a median age of 13 (range 7-16) years were identified, 55 (90%) of whom were photosensitive. Eighteen of these 55 patients showed photosensitivity only after four minutes of continuous photic stimulation. The prevalence of photosensitivity in juvenile myoclonic epilepsy is likely to be higher than previously reported. When a diagnosis of juvenile myoclonic epilepsy is being considered, the initial diagnostic EEG should include intermittent photic stimulation for up to five minutes, or less if the patient shows evidence of photosensitivity. The identification of photosensitivity may have important management implications.

Decreased arterial carbon dioxide tension (PaCO 2 ) results in decreased cerebral blood flow, which is associated with diminished cerebral electrical activity. In such a situation, cerebral fractional oxygen extraction (CFOE) would be expected to increase to preserve cerebral oxygen delivery. This study aimed to determine whether changes in blood gases in infants less than 30 wk' gestation were associated with changes in background electroencephalograms (EEG) and CFOE. Thirty-two very low birth weight infants were studied daily for the first three days after birth. Digital EEG recordings were performed for 75 min each day. CFOE, mean blood pressure and arterial blood gases were measured midway through each recording. EEG was analysed by (a) spectral analysis and (b) manual calculation of interburst interval. Blood pressure, pH and PaCO 2 did not have any effect on the EEG. On day one, only PaCO 2 showed a relationship with the relative power of the delta frequency band (0.5-3.5 Hz) and the interburst interval. The relative power of the delta band remained within normal limits when PaCO 2 was between 24 and 55 mm Hg on day one. There was a negative association between PaCO 2 and CFOE. The associations between PaCO 2 and EEG measurements were strongest on day one, weaker on day two, and absent on day three. The slowing of EEG and increased CFOE at lower levels of PaCO 2 are likely to be due to decreased cerebral oxygen delivery induced by hypocarbia. When PaCO 2 was higher, there was suppression of the EEG. Periventricular leukomalacia is an important cause of neurologic morbidity in very low birth weight infants (1) and has been associated with severe hypocarbia during the first 24 h after birth. This effect of arterial carbon dioxide tension (PaCO 2 ) on the brain is likely to be mediated through its effect on cerebral blood flow, which is decreased by hypocarbia. In such a situation, cerebral fractional oxygen extraction (CFOE) would be expected to increase, as cerebral oxygen delivery is reduced (8). Decreased cerebral oxygen delivery would also be expected to be associated with reduced cerebral electrical activity. A positive relationship between cerebral blood flow and integrated amplitude of the EEG has been demonstrated on a group of infants between 27 and 33 wk' gestation (9). However, no studies have described the relationship between background cerebral electrical activity and PaCO 2 in very low birth weight infants.Electroencephalography provides a noninvasive technique for monitoring cerebral electrical activity. The normal EEG pattern of infants less than 30 wk' gestation is markedly discontinuous and consists of long isoelectric periods called interburst intervals, interspersed with bursts of high voltage and mixed frequency activity (10). Two separate studies have linked adverse neurologic outcome of such infants with an abnormal background EEG activity characterised by prolonged Received February 18, 2004; accepted November 16, 2004

Cardiac output is a determinant of systemic blood flow and its measurement may therefore be a useful indicator of abnormal hemodynamics and tissue oxygen delivery. The purpose of this study was to investigate in very premature newborn infants the relationships between cardiac output (left and right ventricular outputs), systemic blood pressure, peripheral blood flow (PBF) and two indicators of cerebral oxygen delivery (cerebral electrical activity and cerebral fractional oxygen extraction (CFOE)). This was a prospective observational study performed on 40 infants of less than 30 wk gestation. Digital electroencephalograms (EEGs) were recorded for one hour every day during the first four days after birth and subjected to qualitative and quantitative analysis. Left and right ventricular outputs, mean blood pressure (MBP), CFOE, PBF and arterial blood gases were measured at the same time. Within the ranges studied, there was no apparent relationship between left or right ventricular output (RVO), PBF and indicators of cerebral perfusion (cerebral electrical activity and CFOE). The EEG was normal in infants with low left and right ventricular outputs (Ͻ150 mL/kg/min) and MBP Ͼ 30 mm Hg. Infants with low cardiac output and normal MBP seem able to maintain cerebral perfusion, possibly through vasodilatation of the cerebral microvasculature. Clinicians rely on its absolute value to guide therapy and the prescription of volume expanders and inotropes. However, systemic blood pressure is the product of systemic vascular resistance and cardiac output and is not a direct indicator of the systemic blood flow. Nevertheless, the clinician's approach is based on the assumption that hypotension causes decreased organ perfusion, including that of the brain, resulting in tissue damage. Furthermore, the relationship between MBP and cerebral blood flow remains unclear (1,2); it is presumed that cerebral blood flow is preserved by autoregulation even in very preterm babies but the limits of autoregulation are uncertain.Although cardiac output might reasonably be expected to be a major determinant of systemic blood flow (and therefore of tissue oxygen delivery), the relationship is not a simple one.Thus, a study of preterm infants with closed or insignificant patent ductus arteriosus, showed a weak but significant correlation between mean blood pressure (MBP) and left ventricular output (LVO) overall, but LVO was normal for some babies with low MBP, while for others MBP was normal when ventricular output was low (3).There have been relatively few studies of the relationship between cardiac output and cerebral perfusion in the human preterm infant. A recent study of infants between 24 and 30 wk gestation measured cerebral fractional oxygen extraction (CFOE) as a proxy measure of cerebral oxygen delivery: CFOE is increased when cerebral oxygen delivery is low. There was a weak but significant negative correlation between LVO and cerebral fractional oxygen extraction (4). Infants were particularly vulnerable to poor cerebral o...

A persistent focal abnormality was observed in 157 (16%) electroencephalograms undertaken in 964 consecutive children with epileptic and non-epileptic seizures seen over one year. CT head scans were performed in 121 (77%) of the 157 children with a focus on the EEG; 26 (21%) showed an abnormality, and 21 (81%) of the abnormalities were localised. There was no difference in the proportion of abnormal scans associated with a delta or slow wave focus compared with a spike or sharp wave focus. An abnormal scan was uncommon after a single seizure. In only two patients (1.7% of all scans) did the findings on CT alter or greatly influence subsequent management. ( Neurol Neurosurg Psychiatry 1993;56:369-37 Scans were performed with a third generation Siemens Somatrom 2 scanner before and after intravenous contrast and with specific views of the temporal lobes. Records showing symmetric, posterior slow waves of youth, bilateral multifocal abnormalities, and asymmetry of background rhythmic activity (without any focal abnormality) were excluded from the study. Reactiveness of the focal slow wave abnormality was not assessed.Statistical analysis of the CT and EEG appearances used the X2 test. Repeat or follow up EEGs were undertaken in about a quarter of subjects but these data have not been analysed in this report. ResultsEEGs were recorded in 964 consecutive patients, aged 2 months to 17 years (mean 8 years). A total of 182 patients had had a single witnessed seizure; the remaining 782 patients had had at least two seizures. It was difficult to ascertain what proportion of these 782 patients had epilepsy as they were not all under the care of the authors and clinical information was therefore limited. However, at least 530 were considered to have epilepsy.The records showed a continuous, persistent, or recurring focal abnormality in 157 patients (16%), of which 83 were slow waves and 74 were spike or sharp wave foci. Three of the 157 patients showed both a slow wave and epileptiform focus. CT head scans were performed in 121 of the 157 patients (77%) with an EEG focus. CT was not recommend-369 on 12 May 2018 by guest. Protected by copyright.

The audit form was divided into two sections; the first recorded information from the EEG request including (a) clinical information, age and sex of patient, age of onset and seizure details, neurological findings, and family history required to facilitate syndrome recognition; drug history and handedness (relevant for o rhythm and other changes in background activity); (b) provisional diagnosis; and (c) purpose of EEG. The second part focused on the value of EEG in clinical practice and was subdivided into the following three areas: (a) request appropriateness; (b) diagnostic index yield (syndrome, generalised, focal, non-specific, and normal); and (c) usefulness of the electroclinical report.An audit form for each patient was completed at the time that the results of the EEG were reported. Statistical analysis of the comparison of data obtained from both surveys was by x2.Results There were 165 consecutive requests for EEG in the first two month period. There were 195 requests in the second period, but only the first 165 were analysed, allowing a comparison between populations of identical size. Sources of requests were almost identical in the two surveys, originating from hospital (80%) and