EEG Background Activity Research Articles

Electroencephalography during general anaesthesia differs between term-born and premature-born children

ObjectivesPremature birth is associated with a wide range of complications in later life, including structural and functional neurological abnormalities and altered pain sensitivity. We investigated whether during anaesthesia premature-born children display different patterns of background EEG activity and exhibit increased responses to nociceptive stimuli. MethodsWe examined background EEG and time-locked responses to clinical cannulation in 45 children (mean age (±SD) at study: 4.9(±3.0)years) under sevoflurane monoanaesthesia maintained at a steady-state end-tidal concentration of 2.5%. 15 were born prematurely (mean gestational age at birth: 29.2±3.9weeks) and 30 were age-matched term-born children. ResultsBackground levels of alpha and beta power were significantly lower in the premature-born children compared to term-born controls (p=0.048). Clinical cannulation evoked a significant increase in delta activity (p=0.032), which was not significantly different between the two groups (p=0.44). ConclusionsThe results indicate that whilst under anaesthesia premature-born children display different patterns of background brain activity compared to term-born children. SignificanceAs electrophysiological techniques are increasingly used by anaesthetists to gauge anaesthetic depth, differences in background levels of electrophysiological brain activity between premature and term-born children may be relevant when considering titration of anaesthetic dose.

Editorial: Bridging the gap before and after birth: methods and technologies to explore the functional neural development in humans.

Editorial: Bridging the gap before and after birth: methods and technologies to explore the functional neural development in humans.

EEG reactivity to pain in comatose patients: Importance of the stimulus type.

Electroencephalogram (EEG) background reactivity is a potentially interesting outcome predictor in comatose patients, especially after cardiac arrest, but recent studies report only fair interrater reliability. Furthermore, there are no definite guidelines for its testing. We therefore investigated the EEG effect of standardized noxious stimuli in comatose patients not reactive to auditory stimuli. In this prospective study we applied a protocol using three different painful stimuli (bilateral nipple pinching, pinprick at the nose base, finger-nail compression on each side), grouped in three distinct clusters with an alternated sequence, during EEG recordings in comatose patients. We only analyzed recordings showing any reactivity to pain. Fisher and χ2 tests were used as needed to assess contingency tables. Of 42 studies, 12 did not show any background reactivity, 2 presented SIRPIDs, and 2 had massive artefacts; we thus analyzed 26 EEGs recorded in 17 patients (4 women, 24%). Nipple pinching more frequently induced a change in EEG background activity (p<0.001), with a sensitivity of 97.4% for reactivity. Neither the order of the stimuli in the cluster (p=0.723), nor the cluster order (p=0.901) influenced the results. In this pilot study, bilateral, synchronous nipple pinching seems to be the most efficient method to test nociceptive EEG reactivity in comatose patients. This approach may enhance interrater reliability, but deserves confirmation in larger cohorts.

Reduced Cortical Activity Impairs Development and Plasticity after Neonatal Hypoxia Ischemia.

Preterm birth and term birth asphyxia result in brain injury from inadequate oxygen delivery and constitute a major and growing worldwide health problem. Poor outcomes are noted in a majority of very premature (<25 weeks gestation) newborns, resulting in death or life-long morbidity with motor, sensory, learning, behavioral, and language disabilities that limit academic achievement and well-being. Limited progress has been made to develop therapies that improve neurologic outcomes. The overall objective of this study is to understand the effect of early brain injury on activity-dependent brain development and cortical plasticity to develop new treatments that will optimize repair and recovery after brain injury.

Neurophysiologic Evaluation of Children with Beta-Thalassemia Major

Neural pathway involvement is considered to be a neurological complication in Beta-thalassemia major (BTM). This study aimed to detect possible involvement of central and peripheral neural pathways in a group of neurologically asymptomatic patients with BTM. It was performed on 30 patients diagnosed as having BTM (group I), and 10 healthy children who were matched for age, sex, and height (group II). Serum ferritin, iron, glucose tolerance test, intelligence quotient (IQ) test, and electroencephalogram (EEG) were assessed in BTM patients. Electrophysiologic study was assessed in both groups. The mean age of the patients was 10.45 ± 2.88 years. They were 14 males and 16 females. The results of the present study showed that 66.7% of patients had subclinical sensory peripheral neuropathy. Twenty percent of the patients had abnormal somatosensory evoked potentials. Low average and slow learner total IQ score were found in 63.3% of the studied patients. These findings did not correlate with age, disease duration, serum iron, and ferritin. Twenty-three patients had mature EEG background activity, while seven patients had immature background activity. The EEG background maturity had significant correlation with age, duration of desferrioxamine therapy, and serum iron. There was no correlation between serum ferritin level, EEG, and electrophysiologic findings. Regular electrophysiologic monitoring and intellectual evaluation are recommended to detect relevant abnormalities and apply appropriate management.

Early prognostication markers in cardiac arrest patients treated with hypothermia

Established prognostication markers, such as clinical findings, electroencephalography (EEG) and biochemical markers, used by clinicians to predict neurological outcome after cardiac arrest (CA) are altered under therapeutic hypothermia (TH) conditions and their validity remains uncertain. MEDLINE and Embase were searched for evidence on the current standards for neurological outcome prediction for out-of-hospital CA patients treated with TH and the validity of a wide range of prognostication markers. Relevant studies that suggested one or several established biomarkers and multimodal approaches for prognostication are included and reviewed. Whilst the prognostic accuracy of various tests after TH has been questioned, pupillary light reflexes and somatosensory evoked potentials are still strongly associated with negative outcome for early prognostication. Increasingly, EEG background activity has also been identified as a valid predictor for outcome after 72 h after CA and a preferred prognostic method in clinical settings. Neuroimaging techniques, such as magnetic resonance imaging and computed tomography, can identify functional and structural brain injury but are not readily available at the patient's bedside because of limited availability and high costs. A multimodal algorithm composed of neurological examination, EEG-based quantitative testing and somatosensory evoked potentials, in conjunction with newer magnetic resonance imaging sequences, if available, holds promise for accurate prognostication in CA patients treated with TH. In order to avoid premature withdrawal of care, prognostication should be performed more than 72 h after CA.

P136. Relation of EEG frequency and apathy in patients with Parkinson’s disease (PD)

Objective To examine the hypothesis that apathy in patients with PD is related to frontal and temporal changes in EEG frequencies. We expected apathy to correlate with slowing of general EEG background activity, with decrease of alpha power and with increase of theta power in frontal and temporal regions of the brain. Methods 37 non-demented patients with idiopathic PD were recruited from the Movement Disorder Outpatient Clinic Basel (age: Median 69y; from 50y to 84y; 14 females). The Apathy Evaluation Scale (AES) (Marin, 1991) in informant version (AES-I) were completed by relatives of the patients.256-channel EEGs with quantitative semi-automatic analyses were used to detect alpha total-frequencies alpha 1-, alpha 2- and theta-in frontal and temporal regions. In addition, slowing of EEG was measured with Median Peak frequency. For statistics, a general linear model with backward elimination procedure was conducted. We controlled for confounding factors: age, gender, education, severity of motor symptoms, levodopa equivalent dose, depression and cognition. Results In this sample, the patients were only slightly affected by apathy ( Median =24; from 18 to 39; cut off value: 38). The resulting model was significant ( R 2 = 0.39 ; p b =−3.74; p =0.08). Relevant variables in the resulting model were alpha total, temporal right ( b =76.493; p b =−58.37; p b =−13.07; p r =−0.40), whereas in females there was no correlation between alpha total and the number of apathy symptoms ( r =0.04). Conclusions Slowing of EEG is correlated with apathy in patients with PD. This correlation is significant even in PD patients with little or no depression. This fact helps to separate the two neuropsychiatric entities. In accordance with our hypothesis, beginning apathy in PD might be related to an alpha 1 decrease the frontal left part of the brain. In contrast, alpha total of the right hemisphere positively correlates with apathy. In addition, however, the results in male gender are consistent with our expectation, but have to be replicated in a larger sample of PD patients with more severe apathy.

Interplay between impaired brain structure and function in term newborns with congenital heart disease

Background: Term neonates with congenital heart disease (CHD) demonstrate a high incidence of white matter injury (WMI), together with increased average diffusivity and decreased fractional anisotropy (FA) on MR diffusion tensor imaging. EEG background activity is a robust measure of functional brain maturation that becomes less discontinuous, contains more fast activity and shows higher complexity of EEG patterns with increasing age. We sought to determine the association between structural brain abnormalities and functional brain maturation in term neonates with CHD. Methods: Thirteen term newborns with CHD underwent pre-operative MR imaging and continuous EEG recordings (cEEG). The proportion of cEEG with discontinuous vs. continuous background activity was quantified by visual analysis. During continuous epochs, we differentiated between two states: wakefulness/active sleep vs. quiet/transitional sleep, and applied algorithms to measure spectral power and EEG complexity. Results: Three patients had multifocal WMI which was associated with greater EEG background discontinuity (P&lt;0.05). Moreover, lower white matter diffusivity was associated with higher power of fast activity (P&lt;0.05 for wakefulness/active sleep EEG pattern), while higher white matter FA showed a trend toward being associated with increased EEG complexity (P&lt;0.1 for quiet/transitional sleep pattern). Conclusions: In this series of term neonates with CHD, structural and microstructural white matter abnormalities are associated with impaired maturation of brain function.

Objective differentiation of neonatal EEG background grades using detrended fluctuation analysis.

A quantitative and objective assessment of background electroencephalograph (EEG) in sick neonates remains an everyday clinical challenge. We studied whether long range temporal correlations quantified by detrended fluctuation analysis (DFA) could be used in the neonatal EEG to distinguish different grades of abnormality in the background EEG activity. Long-term EEG records of 34 neonates were collected after perinatal asphyxia, and their background was scored in 1 h epochs (8 h in each neonate) as mild, moderate or severe. We applied DFA on 15 min long, non-overlapping EEG epochs (n = 1088) filtered from 3 to 8 Hz. Our formal feasibility study suggested that DFA exponent can be reliably assessed in only part of the EEG epochs, and in only relatively short time scales (10–60 s), while it becomes ambiguous if longer time scales are considered. This prompted further exploration whether paradigm used for quantifying multifractal DFA (MF-DFA) could be applied in a more efficient way, and whether metrics from MF-DFA paradigm could yield useful benchmark with existing clinical EEG gradings. Comparison of MF-DFA metrics showed a significant difference between three visually assessed background EEG grades. MF-DFA parameters were also significantly correlated to interburst intervals quantified with our previously developed automated detector. Finally, we piloted a monitoring application of MF-DFA metrics and showed their evolution during patient recovery from asphyxia. Our exploratory study showed that neonatal EEG can be quantified using multifractal metrics, which might offer a suitable parameter to quantify the grade of EEG background, or to monitor changes in brain state that take place during long-term brain monitoring.

Clinical, Electroencephalographic, and Neuroradiological Outcome Predictors in Acute Nonhypoxic Encephalopathy: A Nine-Year Cohort Study.

Marked impairment of consciousness, brain lesion on neuroimaging, and nonreactive electroencephalographic (EEG) background activity are established outcome predictors in patients with hypoxic encephalopathy. In this observational cohort study, we aimed to assess the predictive value of clinical, neuroimaging and EEG characteristics for outcome in different types of acute nonhypoxic encephalopathic patients. All adult intensive care unit patients from a tertiary academic medical care center with clinical and EEG evidence of acute nonhypoxic encephalopathy were included from 2004 to 2012. Clinical data, neuroimaging studies, EEG characteristics, and outcome were assessed. In-hospital death was the main outcome. Median age of 262 patients was 65 years (range 18-98 years). Mortality was 12.6%. In Poisson regression analyses, older age (P=.02), intracranial hemorrhage (P=.008), coma (P=.012), and nonreactive EEG background activity (P<.0001) were independently associated with death with nonreactive EEG being the strongest predictor (relative risk 3.74; 95% confidence interval 2.02-6.91). Subgroup analysis revealed no significant effect modification for the predictive value of nonreactive EEG by the presence or absence of coma and different types of acute brain lesions. In conclusion, this study identifies and quantifies the independent predictive value of older age, intracranial hemorrhage, coma, and nonreactive EEG for death, in patients with different types of acute nonhypoxic encephalopathy. These results add further credence to the limited body of evidence that EEG provides important prognostic information in different types of acute encephalopathy not related to hypoxic brain injury. Further studies are warranted to analyze the robustness of this predictor in larger subpopulations with specific etiologies of acute nonhypoxic encephalopathies.

Advanced analysis of auditory evoked potentials in hyperthyroid patients: the effect of filtering.

The purpose of the study is to evaluate Auditory Evoked Potentials (AEPs) in patients with hyperthyroidism and to compare their frequency components with those of healthy subjects. In this study the AEPs in hyperthyroidism were studied both in time and frequency domains rather than studying just in the time domain by peak scoring. This paper presents a method for filtering auditory oddball standard and target AEPs by using singular spectrum analysis (SSA) and feature extraction in the frequency domain via spectral analysis. AEPs were recorded during an auditory oddball paradigm in 25 newly diagnosed hyperthyroid patients and 15 healthy subjects. The signals are captured in the presence of ongoing background EEG activity so they are often contaminated by artifacts. This paper presents a method for filtering auditory odd-ball standard and target AEPs by using Singular spectrum analysis and feature extraction in frequency domain via spectral analysis. Information about the frequency composition of the signal is then used to compare normal and hyperthyroid states. While there was no significant difference either in the target or standard unfiltered signals between the hyperthyroid patients and the control group (p > 0.05), there was a significant difference in the filtered signals between the two groups (p < 0.01). In conclusion, our results revealed that SSA is an effective filtering method for AEPs. Thus, a much more objective and specific examination method was developed.

EEG in the neonatal unit

The execution and interpretation of neonatal EEG adheres to strict and specific criteria related to this very early age. In preterm newborns, the dedicated healthcare staff needs to respect EEG indications and chronology of EEG recordings in order to diagnose and manage various pathologies, and use EEG in addition to cerebral imaging. EEG analysis focuses on a global vision of the recording according to the neonate's state of alertness and various age-related patterns. Monitoring of continuous conventional EEG and simplified EEG signal processing can help screen for seizures and monitor the effect of antiepileptic treatment, as well as appreciating changes in EEG background activity, for diagnostic and prognostic purposes. EEG reports should be highly explanatory to meet the expectations of the physician's clinical request.

Continuous EEG monitoring in children in the intensive care unit (ICU)

Pediatric EEG in the intensive care unit (ICU) requires specific technical requirements in order to yield relevant data depending upon clinical scenario: diagnosis of electroclinical or subclinical seizures, their quantification before and after therapeutic changes and sometimes evaluation of severity of cortical dysfunction. The urgent nature of these indications implies the rapid set-up of the EEG system by qualified staff and possibility of maintaining the electrodes in place during long periods of time. Various techniques are available today for EEG monitoring, the interpretation of which depends on the contribution of an experienced physician. Among recent techniques, those most commonly used are trend curves obtained via signal analysis such as amplitude EEG (a-EEG) and density spectral array (DSA) or compressed spectral array (CSA). Trend curves enable the digital creation of a display graph containing several hours of transformed and compressed EEG recorded data. Visualized on one sole display graph, these trend curves can facilitate the identification of very slow changes in EEG background activity and their variation (alertness cycles, changes linked to treatment administrations) as well as seizure patterns and their quantification. In this chapter, we propose a brief overview of monitoring techniques, followed by a review of the various data yielded by EEG monitoring as well as the relevance of this type of management; finally, detailed clinical indications will be discussed after thorough analysis of the literature.

Noise power associated with decreased task-induced variability of brain electrical activity in schizophrenia.

In schizophrenia, both increased baseline metabolic and electroencephalographic (EEG) activities as well as decreased task-related modulation of neural dynamics have been reported. Noise power (NP) can measure the background EEG activity during task performance, and Shannon entropy (SE) is useful for quantifying the global modulation of EEG activity with a high temporal resolution. In this study, we have assessed the possible relationship between increased NP in theta and gamma bands and decreased SE modulation in 24 patients with schizophrenia and 26 controls over the parietal and central regions during a P300 task. SE modulation was calculated as the change from baseline to the active epoch (i.e., 150-550 ms following the target stimulus onset). Patients with schizophrenia displayed statistically significant higher NP values and lower SE modulation than healthy controls. We found a significant association between gamma NP and SE in all of the participants. Specifically, a NP increase in the gamma band was followed by a decrease in SE change. These results support the notion that an excess of gamma activity, unlocked to the task being performed, is accompanied by a decreased modulation of EEG activity in schizophrenia.

Electroencephalographic aspects in dogs with congenital hydrocephalus

Introduction: Congenital hydrocephalus (CH) is a common neurologic disorder in dogs defined as an increased cerebrospinal fluid volume within the cranial cavity with no any specific causes. The diagnosis of this disease is based on the clinical features and imagistic examination (ultrasonography, CT, MRI) of the brain. Electroencephalography (EEG) is the best electrodiagnostic test in trying to assess the impact of hydrocephalus on electric activity of the brain . T he aim of this study is to describe short time EEG changes in dogs with CH. Materials and Methods: EEG was performed on 6 dogs with congenital hydrocephalus under general anaesthesia with medetomidine hydrochloride 0.05 mg/kg inj. EEGs were obtained via five subdermal stainless steel needle electrodes as described by Redding (1978). In EEG recoding the parameters used were: sensitivity = 70I¼V/cm; time constant = 0.3 seconds; Hf = 70 Hz; Lf = 0.5 Hz; notch filter inserted; impedance of all electrodes < 10 kI©. The results of the present study revealed abnormalities in EEG background activity in all dogs. Focal abnormalities were seen in 5 patients (slow waves in 2 dogs, spikes and sharp waves in 2 dogs, focal attenuation in 2 cases) and generalized abnormal activities in 4 dogs (generalized slow waves in 4 dogs and generalised spikes and sharp waves in 1 dog). The percentage of EEG interictal epileptiform discharges (66.67% of dogs had spikes, sharp waves, spikes and sharp waves complexes) was greater than seizures clinical seen (33.33% of dogs). In conclusion , EEG gived us important information about the severity of changes induced by hydrocephalus. Furthermore, this test is useful in the diagnosis of seizures associated with hydrocephalus and allows monitoring the therapeutic effects of antiepileptic drugs.

Slowing of EEG background activity in Parkinson's and Alzheimer's disease with early cognitive dysfunction.

Background: Slowing of the electroencephalogram (EEG) is frequent in Parkinson’s (PD) and Alzheimer’s disease (AD) and correlates with cognitive decline. As overlap pathology plays a role in the pathogenesis of dementia, it is likely that demented patients in PD show similar physiological alterations as in AD.Objective: To analyze distinctive quantitative EEG characteristics in early cognitive dysfunction in PD and AD.Methods: Forty patients (20 PD- and 20 AD patients with early cognitive impairment) and 20 normal controls (NC) were matched for gender, age, and education. Resting state EEG was recorded from 256 electrodes. Relative power spectra, median frequency (4–14 Hz), and neuropsychological outcome were compared between groups.Results: Relative theta power in left temporal region and median frequency separated the three groups significantly (p = 0.002 and p < 0.001). Relative theta power was increased and median frequency reduced in patients with both diseases compared to NC. Median frequency was higher in AD than in PD and classified groups significantly (p = 0.02).Conclusion: Increase of theta power in the left temporal region and a reduction of median frequency were associated with presence of AD or PD. PD patients are characterized by a pronounced slowing as compared to AD patients. Therefore, in both disorders EEG slowing might be a useful biomarker for beginning cognitive decline.

Valproate treatment normalizes EEG functional connectivity in successfully treated idiopathic generalized epilepsy patients

To investigate the effect of chronic VPA treatment of EEG functional connectivity in successfully treated idiopathic generalized epilepsy (IGE) patients. 19-channel waking, resting-state EEG records of 26 IGE patients were analyzed before treatment (IGE) and after the 90th day of treatment (VPA), in seizure-free condition. Three minutes of artifact-free EEG background activity (without epileptiform potentials) was analyzed for each patient in both conditions. A group of 26 age-matched healthy normative control persons (NC) was analyzed in the same way. All the EEG samples were processed to LORETA (Low Resolution Electromagnetic Tomography) to localize multiple distributed sources of EEG activity. Current source density time series were generated for 33 regions of interest (ROI) in each hemisphere for four frequency bands. Pearson correlation coefficients (R) were computed between all ROIs in each hemisphere, for four bands across the investigated samples. R values corresponded to intrahemispheric, cortico-cortical functional EEG connectivity (EEGfC). Group and condition differences were analyzed by statistical parametric network method. p<0.05, corrected for multiple comparisons: (1) The untreated IGE group showed increased EEGfC in the delta and theta bands, and decreased EEGfC in the alpha band (as compared to the NC group); (2) VPA treatment normalized EEGfC in the delta, theta and alpha bands; and (3) degree of normalization depended on frequency band and cortical region. VPA treatment normalizes EEGfC in IGE patients.

Corticosteroid therapy in regressive autism: a retrospective study of effects on the Frequency Modulated Auditory Evoked Response (FMAER), language, and behavior.

BackgroundUp to a third of children with Autism Spectrum Disorder (ASD) manifest regressive autism (R-ASD).They show normal early development followed by loss of language and social skills. Absent evidence-based therapies, anecdotal evidence suggests improvement following use of corticosteroids. This study examined the effects of corticosteroids for R-ASD children upon the 4 Hz frequency modulated evoked response (FMAER) arising from language cortex of the superior temporal gyrus (STG) and upon EEG background activity, language, and behavior. An untreated clinical convenience sample of ASD children served as control sample.MethodsTwenty steroid-treated R-ASD (STAR) and 24 not-treated ASD patients (NSA), aged 3 - 5 years, were retrospectively identified from a large database. All study participants had two sequential FMAER and EEG studies;Landau-Kleffner syndrome diagnosis was excluded. All subjects’ records contained clinical receptive and expressive language ratings based upon a priori developed metrics. The STAR group additionally was scored behaviorally regarding symptom severity as based on the Diagnostic and Statistical Manual IV (DSM-IV) ASD criteria list. EEGs were visually scored for abnormalities. FMAER responses were assessed quantitatively by spectral analysis. Treated and untreated group means and standard deviations for the FMAER, EEG, language, and behavior, were compared by paired t-test and Fisher’s exact tests.ResultsThe STAR group showed a significant increase in the 4 Hz FMAER spectral response and a significant reduction in response distortion compared to the NSA group. Star group subjects’ language ratings were significantly improved and more STAR than NSA group subjects showed significant language improvement. Most STAR group children showed significant behavioral improvement after treatment. STAR group language and behavior improvement was retained one year after treatment. Groups did not differ in terms of minor EEG abnormalities. Steroid treatment produced no lasting morbidity.ConclusionsSteroid treatment was associated with a significantly increased FMAER response magnitude, reduction of FMAER response distortion, and improvement in language and behavior scores. This was not observed in the non-treated group. These pilot findings warrant a prospective randomized validation trial of steroid treatment for R-ASD utilizing FMAER, EEG, and standardized ASD, language and behavior measures, and a longer follow-up period.Please see related article http://www.biomedcentral.com/1741-7015/12/79

Spectral Characteristics of the Ongoing Electroencephalogram in Children Suffering from Visual Dysfunctions

We recorded ongoing EEG and measured mean values of the modal frequency (MF), absolute spectral power (ASP), and relative (normalized) spectral power (RSP) of the delta, theta, alpha rhythms, and beta1 and beta2 subrhythms in 31 children with inborn visual dysfunctions (average intragroup visual acuity of about 0.2) and 49 children with normal vision (age, from 8 to 12 years). Background EEG activity in children with visual dysfunctions was characterized by lower ASPs of all EEG frequency ranges (maximally, of the alpha rhythm), a lower RSP of alpha oscillations against the background of a higher RSP of the delta range (and that of beta2 subrange in boys), and also by higher MFs of slow-wave activity and of beta oscillations (beta2 and beta1 subranges in girls and boys, respectively); the MF of alpha activity in most cortical regions was unchanged. The data obtained are probably indicative of increased activity of the caudal brainstem regions related to the existence of visual dysfunctions; this results in changes in the pattern of interaction between activating and deactivating cerebral systems. Possible compensatory mechanisms influencing integrative activity of the brain under conditions of visual dysfunctions are discussed.

The Effect of Blood Glucose and pCO2 on Spectral EEG of Premature Infants during the First Three Days of Life

Background: Spectral EEG analysis using automated quantification of total absolute band power (tABP) expresses brain function. We hypothesized that pCO₂ or blood glucose affects tABP during the critical first days of life in premature infants. Objective: To use automated tABP quantification to determine whether EEG background activity in premature infants during the first 3 days of life is influenced by pCO₂ or blood glucose levels. Methods: Preterm infants, group 1 [gestational age (GA) = 24-27 weeks] and group 2 (GA = 28-30 weeks), underwent continuous EEG monitoring for 3 days after birth. Biochemical data were extracted from the observational datasheet used during monitoring. Blood samples were taken at the request of the attending physician. Statistical analyses were performed as repeated measurements using linear mixed models with a random intercept. The effect of time was treated as a fixed covariate and the GA groups as a fixed factor in all models. Continuous data were described using the mean ± SD or median and range, and categorical data were described using the number of patients and percentages unless otherwise indicated. Results: There was an association between increased pCO₂ and tABP and between increased blood glucose and tABP. Further, there were no differences in the responses between groups 1 and 2. Conclusion: Both hyperglycemia and hypercapnia showed a negative effect on brain activity decreasing tABP during the first 3 days of life in premature infants.